Merge upstream

89 files changed, 1343 insertions, 768 deletions

diff --git a/AUTHORS b/AUTHORS
index 17fe246de..7f00f91f1 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -11,3 +11,8 @@ Original Authors "mruby developers" are:
    Masaki Muranaka
    Internet Initiative Japan Inc.
    Tadashi FUKUZAWA
+   MATSUMOTO Ryosuke
+   Yasuhiro Matsumoto
+   Koji Yoshioka
+   Jun Hiroe
+   Narihiro Nakamura
diff --git a/README.md b/README.md
index 28e2ffc71..9bcffacf7 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
     This is a preliminary release for internal team review.
     The URLs and addresses described below are not available yet.
     The official release will be announced later.
-    Any suggestion for modification is welcome.
+    Any suggestions for modification are welcome.
     Delays in replies are to be expected. Sorry in advance.
 
 ## What's mruby
@@ -113,4 +113,4 @@ Please ask us if you want to distribute your code under another license.
 See the [contribution guidelines](https://github.com/mruby/mruby/blob/master/CONTRIBUTING.md)
 then send a pull request to <http://github.com/mruby/mruby>.  We consider you have granted
 non-exclusive right to your contributed code under MIT license.  If you want to be named
-as one of mruby developers, include update to the AUTHORS file in your pull request.
+as one of mruby developers, please include an update to the AUTHORS file in your pull request.
diff --git a/doc/compile/README.md b/doc/compile/README.md
index a244d06b2..e7f382f15 100644
--- a/doc/compile/README.md
+++ b/doc/compile/README.md
@@ -33,7 +33,8 @@ customized path using the *$MRUBY_CONFIG* environment variable.
 
 To compile just call ```./minirake``` inside of the mruby source root. To
 generate and execute the test tools call ```./minirake test```. To clean
-all build files call ```./minirake clean```.
+all build files call ```./minirake clean```. To see full command line on 
+build, call ```./minirake -v```.
 
 ## Build Configuration
 
@@ -177,6 +178,7 @@ Integrate GEMs in the build process.
 	conf.gem 'path/to/another/gem'
 
 
+See doc/mrbgems/README.md for more option about mrbgems.
 ### Mrbtest
 
 Configuration Mrbtest build process.
diff --git a/doc/mrbgems/README.md b/doc/mrbgems/README.md
index e89fd1a56..881fbb228 100644
--- a/doc/mrbgems/README.md
+++ b/doc/mrbgems/README.md
@@ -25,6 +25,9 @@ A remote GIT repository location for a GEM is also supported:
 
 	conf.gem :bitbucket => 'mruby/mrbgems-example', :branch => 'master'
 
+To pull all gems from remote GIT repository on build, call ```./minirake -p```, 
+or ```./minirake --pull-gems```.
+
 NOTE: `:bitbucket` option supports only git. Hg is unsupported in this version.
 
 ## GemBox
@@ -96,7 +99,7 @@ GEM directory. A typical GEM specification could look like this for example:
 
 	MRuby::Gem::Specification.new('c_and_ruby_extension_example') do |spec|
 	  spec.license = 'MIT'
-	  spec.authors = 'mruby developers'
+	  spec.author  = 'mruby developers'
 	end
 
 The mrbgems build process will use this specification to compile Object and Ruby
@@ -121,7 +124,7 @@ In case your GEM is depending on other GEMs please use
 
 	MRuby::Gem::Specification.new('c_and_ruby_extension_example') do |spec|
 	  spec.license = 'MIT'
-	  spec.authors = 'mruby developers'
+	  spec.author  = 'mruby developers'
 
 	  # add GEM dependency mruby-parser.
 	  # Version has to be between 1.0.0 and 1.5.2
diff --git a/examples/mrbgems/c_and_ruby_extension_example/mrbgem.rake b/examples/mrbgems/c_and_ruby_extension_example/mrbgem.rake
index 35dbe5e18..a1f964b36 100644
--- a/examples/mrbgems/c_and_ruby_extension_example/mrbgem.rake
+++ b/examples/mrbgems/c_and_ruby_extension_example/mrbgem.rake
@@ -1,6 +1,6 @@
 MRuby::Gem::Specification.new('c_and_ruby_extension_example') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
  
   # Add compile flags
   # spec.cc.flags << ''
diff --git a/examples/mrbgems/c_extension_example/mrbgem.rake b/examples/mrbgems/c_extension_example/mrbgem.rake
index 8c132b233..3524e22f4 100644
--- a/examples/mrbgems/c_extension_example/mrbgem.rake
+++ b/examples/mrbgems/c_extension_example/mrbgem.rake
@@ -1,6 +1,6 @@
 MRuby::Gem::Specification.new('c_extension_example') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
  
   # Add compile flags
   # spec.cc.flags << '-g'
diff --git a/examples/mrbgems/ruby_extension_example/mrbgem.rake b/examples/mrbgems/ruby_extension_example/mrbgem.rake
index 3a80b5cd7..5624c33e9 100644
--- a/examples/mrbgems/ruby_extension_example/mrbgem.rake
+++ b/examples/mrbgems/ruby_extension_example/mrbgem.rake
@@ -1,6 +1,6 @@
 MRuby::Gem::Specification.new('ruby_extension_example') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
  
   # Add compile flags
   # spec.cc.flags << ''
diff --git a/examples/targets/ArduinoDue.rb b/examples/targets/ArduinoDue.rb
index c45efb57c..a4af4a926 100644
--- a/examples/targets/ArduinoDue.rb
+++ b/examples/targets/ArduinoDue.rb
@@ -5,6 +5,8 @@
 MRuby::CrossBuild.new("Arduino Due") do |conf|
   toolchain :gcc
 
+  # Mac OS X
+  # ARDUINO_PATH = '/Applications/Arduino.app/Contents/Resources/Java'
   # GNU Linux
   ARDUINO_PATH = '/opt/arduino'
   BIN_PATH = "#{ARDUINO_PATH}/hardware/tools/g++_arm_none_eabi/bin"
@@ -13,18 +15,28 @@ MRuby::CrossBuild.new("Arduino Due") do |conf|
 
   conf.cc do |cc|
     cc.command = "#{BIN_PATH}/arm-none-eabi-gcc"
-    cc.include_paths << ["#{SAM_PATH}/system/libsam -I#{SAM_PATH}/system/CMSIS/CMSIS/Include/",
+    cc.include_paths << ["#{SAM_PATH}/system/libsam", "#{SAM_PATH}/system/CMSIS/CMSIS/Include/",
                         "#{SAM_PATH}/system/CMSIS/Device/ATMEL/",
-                        "#{SAM_PATH}/cores/arduino -I#{TARGET_PATH}"]
+                        "#{SAM_PATH}/cores/arduino", "#{SAM_PATH}/libraries","#{TARGET_PATH}"]
     cc.flags = %w(-g -Os -w -ffunction-sections -fdata-sections -nostdlib --param max-inline-insns-single=500 
                 -Dprintf=iprintf -mcpu=cortex-m3 -DF_CPU=84000000L -DARDUINO=152 -D__SAM3X8E__ -mthumb -DUSB_PID=0x003e -DUSB_VID=0x2341 -DUSBCON)
     cc.compile_options = "%{flags} -o %{outfile} -c %{infile}"
+
+    #configuration for low memory environment
+    cc.defines << %w(MRB_HEAP_PAGE_SIZE=64)
+    cc.defines << %w(MRB_USE_IV_SEGLIST)
+    cc.defines << %w(KHASH_DEFAULT_SIZE=8)
+    cc.defines << %w(MRB_STR_BUF_MIN_SIZE=20)
+    cc.defines << %w(MRB_GC_STRESS)
+    #cc.defines << %w(DISABLE_STDIO) #if you dont need stdio.
+    #cc.defines << %w(POOL_PAGE_SIZE=1000) #effective only for use with mruby-eval
   end
 
   conf.cxx do |cxx|
     cxx.command = conf.cc.command.dup
     cxx.include_paths = conf.cc.include_paths.dup
     cxx.flags = conf.cc.flags.dup
+    cxx.defines = conf.cc.defines.dup
     cxx.compile_options = conf.cc.compile_options.dup
   end
 
@@ -36,4 +48,18 @@ MRuby::CrossBuild.new("Arduino Due") do |conf|
   #no executables
   conf.bins = []
 
+  #do not build executable test
+  conf.build_mrbtest_lib_only
+
+  #gems from core
+  conf.gem :core => "mruby-print" 
+  conf.gem :core => "mruby-math"
+  conf.gem :core => "mruby-enum-ext"
+
+  #light-weight regular expression
+  conf.gem :github => "masamitsu-murase/mruby-hs-regexp", :branch => "master" 
+
+  #Arduino API
+  #conf.gem :github =>"kyab/mruby-arduino", :branch => "master"
+
 end
diff --git a/examples/targets/chipKitMax32.rb b/examples/targets/chipKitMax32.rb
index 380a34094..5c3a30a2b 100644
--- a/examples/targets/chipKitMax32.rb
+++ b/examples/targets/chipKitMax32.rb
@@ -24,12 +24,22 @@ MRuby::CrossBuild.new("chipKitMax32") do |conf|
                 -fno-short-double -mprocessor=32MX795F512L -DF_CPU=80000000L -DARDUINO=23 -D_BOARD_MEGA_ 
                 -DMPIDEVER=0x01000202 -DMPIDE=23)
     cc.compile_options = "%{flags} -o %{outfile} -c %{infile}"
+
+    #configuration for low memory environment
+    cc.defines << %w(MRB_HEAP_PAGE_SIZE=64)
+    cc.defines << %w(MRB_USE_IV_SEGLIST)
+    cc.defines << %w(KHASH_DEFAULT_SIZE=8)
+    cc.defines << %w(MRB_STR_BUF_MIN_SIZE=20)
+    cc.defines << %w(MRB_GC_STRESS)
+    #cc.defines << %w(DISABLE_STDIO) #if you dont need stdio.
+    #cc.defines << %w(POOL_PAGE_SIZE=1000) #effective only for use with mruby-eval
   end
 
   conf.cxx do |cxx|
     cxx.command = conf.cc.command.dup
     cxx.include_paths = conf.cc.include_paths.dup
     cxx.flags = conf.cc.flags.dup
+    cxx.defines = conf.cc.defines.dup
     cxx.compile_options = conf.cc.compile_options.dup
   end
 
@@ -41,4 +51,18 @@ MRuby::CrossBuild.new("chipKitMax32") do |conf|
   #no executables
   conf.bins = []
 
+  #do not build test executable 
+  conf.build_mrbtest_lib_only
+
+  #gems from core
+  conf.gem :core => "mruby-print" 
+  conf.gem :core => "mruby-math"
+  conf.gem :core => "mruby-enum-ext"
+
+  #light-weight regular expression
+  conf.gem :github => "masamitsu-murase/mruby-hs-regexp", :branch => "master" 
+
+  #Arduino API
+  #conf.gem :github =>"kyab/mruby-arduino", :branch => "master"
+
 end
diff --git a/include/mruby.h b/include/mruby.h
index 33a15de0e..dcd2aa5fc 100644
--- a/include/mruby.h
+++ b/include/mruby.h
@@ -73,15 +73,15 @@ enum mrb_fiber_state {
 struct mrb_context {
   struct mrb_context *prev;
 
-  mrb_value *stack;
+  mrb_value *stack;                       /* stack of virtual machine */
   mrb_value *stbase, *stend;
 
   mrb_callinfo *ci;
   mrb_callinfo *cibase, *ciend;
 
-  mrb_code **rescue;
+  mrb_code **rescue;                      /* exception handler stack */
   int rsize;
-  struct RProc **ensure;
+  struct RProc **ensure;                  /* ensure handler stack */
   int esize;
 
   uint8_t status;
@@ -97,19 +97,19 @@ enum gc_state {
 typedef struct mrb_state {
   void *jmp;
 
-  mrb_allocf allocf;
+  mrb_allocf allocf;                      /* memory allocation function */
 
   struct mrb_context *c;
   struct mrb_context *root_c;
 
-  struct RObject *exc;
-  struct iv_tbl *globals;
-  struct mrb_irep **irep;
+  struct RObject *exc;                    /* exception */
+  struct iv_tbl *globals;                 /* global variable table */
+  struct mrb_irep **irep;                 /* program data array */
   size_t irep_len, irep_capa;
 
   mrb_sym init_sym;
   struct RObject *top_self;
-  struct RClass *object_class;
+  struct RClass *object_class;            /* Object class */
   struct RClass *class_class;
   struct RClass *module_class;
   struct RClass *proc_class;
@@ -125,17 +125,17 @@ typedef struct mrb_state {
   struct RClass *symbol_class;
   struct RClass *kernel_module;
 
-  struct heap_page *heaps;
+  struct heap_page *heaps;                /* heaps for GC */
   struct heap_page *sweeps;
   struct heap_page *free_heaps;
   size_t live; /* count of live objects */
-  struct RBasic *arena[MRB_ARENA_SIZE];
+  struct RBasic *arena[MRB_ARENA_SIZE];   /* GC protection array */
   int arena_idx;
 
   enum gc_state gc_state; /* state of gc */
   int current_white_part; /* make white object by white_part */
-  struct RBasic *gray_list; /* list of gray objects */
-  struct RBasic *variable_gray_list; /* list of objects to be traversed atomically */
+  struct RBasic *gray_list; /* list of gray objects to be traversed incrementally */
+  struct RBasic *atomic_gray_list; /* list of objects to be traversed atomically */
   size_t gc_live_after_mark;
   size_t gc_threshold;
   int gc_interval_ratio;
@@ -176,12 +176,13 @@ void mrb_undef_class_method(mrb_state*, struct RClass*, const char*);
 mrb_value mrb_instance_new(mrb_state *mrb, mrb_value cv);
 struct RClass * mrb_class_new(mrb_state *mrb, struct RClass *super);
 struct RClass * mrb_module_new(mrb_state *mrb);
-int mrb_class_defined(mrb_state *mrb, const char *name);
+mrb_bool mrb_class_defined(mrb_state *mrb, const char *name);
 struct RClass * mrb_class_get(mrb_state *mrb, const char *name);
+struct RClass * mrb_class_get_under(mrb_state *mrb, struct RClass *outer, const char *name);
 
 mrb_value mrb_obj_dup(mrb_state *mrb, mrb_value obj);
 mrb_value mrb_check_to_integer(mrb_state *mrb, mrb_value val, const char *method);
-int mrb_obj_respond_to(struct RClass* c, mrb_sym mid);
+mrb_bool mrb_obj_respond_to(struct RClass* c, mrb_sym mid);
 struct RClass * mrb_define_class_under(mrb_state *mrb, struct RClass *outer, const char *name, struct RClass *super);
 struct RClass * mrb_define_module_under(mrb_state *mrb, struct RClass *outer, const char *name);
 
@@ -239,9 +240,11 @@ mrb_sym mrb_intern(mrb_state *mrb,const char *cstr)
   return mrb_intern_cstr(mrb, cstr);
 }
 
-void *mrb_malloc(mrb_state*, size_t);
-void *mrb_calloc(mrb_state*, size_t, size_t);
-void *mrb_realloc(mrb_state*, void*, size_t);
+void *mrb_malloc(mrb_state*, size_t);         /* raise RuntimeError if no mem */
+void *mrb_calloc(mrb_state*, size_t, size_t); /* ditto */
+void *mrb_realloc(mrb_state*, void*, size_t); /* ditto */
+void *mrb_realloc_simple(mrb_state*, void*, size_t); /* return NULL if no memory available */
+void *mrb_malloc_simple(mrb_state*, size_t);  /* return NULL if no memory available */
 struct RBasic *mrb_obj_alloc(mrb_state*, enum mrb_vtype, struct RClass*);
 void mrb_free(mrb_state*, void*);
 
@@ -261,15 +264,16 @@ void mrb_p(mrb_state*, mrb_value);
 mrb_int mrb_obj_id(mrb_value obj);
 mrb_sym mrb_obj_to_sym(mrb_state *mrb, mrb_value name);
 
-int mrb_obj_eq(mrb_state*, mrb_value, mrb_value);
-int mrb_obj_equal(mrb_state*, mrb_value, mrb_value);
-int mrb_equal(mrb_state *mrb, mrb_value obj1, mrb_value obj2);
+mrb_bool mrb_obj_eq(mrb_state*, mrb_value, mrb_value);
+mrb_bool mrb_obj_equal(mrb_state*, mrb_value, mrb_value);
+mrb_bool mrb_equal(mrb_state *mrb, mrb_value obj1, mrb_value obj2);
 mrb_value mrb_Integer(mrb_state *mrb, mrb_value val);
 mrb_value mrb_Float(mrb_state *mrb, mrb_value val);
 mrb_value mrb_inspect(mrb_state *mrb, mrb_value obj);
-int mrb_eql(mrb_state *mrb, mrb_value obj1, mrb_value obj2);
+mrb_bool mrb_eql(mrb_state *mrb, mrb_value obj1, mrb_value obj2);
 
 void mrb_garbage_collect(mrb_state*);
+void mrb_full_gc(mrb_state*);
 void mrb_incremental_gc(mrb_state *);
 int mrb_gc_arena_save(mrb_state*);
 void mrb_gc_arena_restore(mrb_state*,int);
@@ -283,13 +287,13 @@ void mrb_field_write_barrier(mrb_state *, struct RBasic*, struct RBasic*);
 } while (0)
 void mrb_write_barrier(mrb_state *, struct RBasic*);
 
-mrb_value mrb_check_convert_type(mrb_state *mrb, mrb_value val, mrb_int type, const char *tname, const char *method);
+mrb_value mrb_check_convert_type(mrb_state *mrb, mrb_value val, enum mrb_vtype type, const char *tname, const char *method);
 mrb_value mrb_any_to_s(mrb_state *mrb, mrb_value obj);
 const char * mrb_obj_classname(mrb_state *mrb, mrb_value obj);
 struct RClass* mrb_obj_class(mrb_state *mrb, mrb_value obj);
 mrb_value mrb_class_path(mrb_state *mrb, struct RClass *c);
-mrb_value mrb_convert_type(mrb_state *mrb, mrb_value val, mrb_int type, const char *tname, const char *method);
-int mrb_obj_is_kind_of(mrb_state *mrb, mrb_value obj, struct RClass *c);
+mrb_value mrb_convert_type(mrb_state *mrb, mrb_value val, enum mrb_vtype type, const char *tname, const char *method);
+mrb_bool mrb_obj_is_kind_of(mrb_state *mrb, mrb_value obj, struct RClass *c);
 mrb_value mrb_obj_inspect(mrb_state *mrb, mrb_value self);
 mrb_value mrb_obj_clone(mrb_state *mrb, mrb_value self);
 
@@ -366,8 +370,8 @@ void mrb_define_global_const(mrb_state *mrb, const char *name, mrb_value val);
 mrb_value mrb_block_proc(void);
 mrb_value mrb_attr_get(mrb_state *mrb, mrb_value obj, mrb_sym id);
 
-int mrb_respond_to(mrb_state *mrb, mrb_value obj, mrb_sym mid);
-int mrb_obj_is_instance_of(mrb_state *mrb, mrb_value obj, struct RClass* c);
+mrb_bool mrb_respond_to(mrb_state *mrb, mrb_value obj, mrb_sym mid);
+mrb_bool mrb_obj_is_instance_of(mrb_state *mrb, mrb_value obj, struct RClass* c);
 
 /* memory pool implementation */
 typedef struct mrb_pool mrb_pool;
@@ -375,9 +379,16 @@ struct mrb_pool* mrb_pool_open(mrb_state*);
 void mrb_pool_close(struct mrb_pool*);
 void* mrb_pool_alloc(struct mrb_pool*, size_t);
 void* mrb_pool_realloc(struct mrb_pool*, void*, size_t oldlen, size_t newlen);
-int mrb_pool_can_realloc(struct mrb_pool*, void*, size_t);
+mrb_bool mrb_pool_can_realloc(struct mrb_pool*, void*, size_t);
 void* mrb_alloca(mrb_state *mrb, size_t);
 
+#ifdef MRB_DEBUG
+#include <assert.h>
+#define mrb_assert(p) assert(p)
+#else
+#define mrb_assert(p) ((void)0)
+#endif
+
 #if defined(__cplusplus)
 }  /* extern "C" { */
 #endif
diff --git a/include/mruby/irep.h b/include/mruby/irep.h
index 856b12099..498b58ca3 100644
--- a/include/mruby/irep.h
+++ b/include/mruby/irep.h
@@ -11,10 +11,11 @@
 extern "C" {
 #endif
 
+/* Program data array struct */
 typedef struct mrb_irep {
   uint32_t idx;
-  uint16_t nlocals;
-  uint16_t nregs;
+  uint16_t nlocals;        /* Number of local variables */
+  uint16_t nregs;          /* Number of register variables */
   uint8_t flags;
 
   mrb_code *iseq;
diff --git a/include/mruby/khash.h b/include/mruby/khash.h
index db8048f5a..fb11586d2 100644
--- a/include/mruby/khash.h
+++ b/include/mruby/khash.h
@@ -27,12 +27,14 @@ typedef khint_t khiter_t;
 //extern uint8_t __m[];
 
 /* mask for flags */
-static const uint8_t __m[8] = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80};
+static const uint8_t __m_empty[8]  = {0x02, 0x08, 0x20, 0x80};
+static const uint8_t __m_del[8]    = {0x01, 0x04, 0x10, 0x40};
+static const uint8_t __m_either[8] = {0x03, 0x0c, 0x30, 0xc0};
 
 
-#define __ac_isempty(e_flag, d_flag, i) (e_flag[(i)/8]&__m[(i)%8])
-#define __ac_isdel(e_flag, d_flag, i) (d_flag[(i)/8]&__m[(i)%8])
-#define __ac_iseither(e_flag, d_flag, i) (__ac_isempty(e_flag,d_flag,i)||__ac_isdel(e_flag,d_flag,i))
+#define __ac_isempty(ed_flag, i) (ed_flag[(i)/4]&__m_empty[(i)%4])
+#define __ac_isdel(ed_flag, i) (ed_flag[(i)/4]&__m_del[(i)%4])
+#define __ac_iseither(ed_flag, i) (ed_flag[(i)/4]&__m_either[(i)%4])
 #define khash_power2(v) do { \
   v--;\
   v |= v >> 1;\
@@ -56,8 +58,7 @@ static const uint8_t __m[8] = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80};
     khint_t size;                                                       \
     khint_t n_occupied;                                                 \
     khint_t upper_bound;                                                \
-    uint8_t *e_flags;                                                   \
-    uint8_t *d_flags;                                                   \
+    uint8_t *ed_flags;                                                  \
     khkey_t *keys;                                                      \
     khval_t *vals;                                                      \
     khint_t mask;                                                       \
@@ -96,14 +97,13 @@ kh_fill_flags(uint8_t *p, uint8_t c, size_t len)
   void kh_alloc_##name(kh_##name##_t *h)                                \
   {                                                                     \
     khint_t sz = h->n_buckets;                                          \
+    uint8_t *p = mrb_malloc(h->mrb, sizeof(uint8_t)*sz/4+(sizeof(khkey_t)+sizeof(khval_t))*sz); \
     h->size = h->n_occupied = 0;                                        \
     h->upper_bound = UPPER_BOUND(sz);                                   \
-    h->e_flags = (uint8_t *)mrb_malloc(h->mrb, sizeof(uint8_t)*sz/4);   \
-    h->d_flags = h->e_flags + sz/8;                                     \
-    kh_fill_flags(h->e_flags, 0xff, sz/8);                              \
-    kh_fill_flags(h->d_flags, 0x00, sz/8);                              \
-    h->keys = (khkey_t *)mrb_malloc(h->mrb, sizeof(khkey_t)*sz);        \
-    h->vals = (khval_t *)mrb_malloc(h->mrb, sizeof(khval_t)*sz);        \
+    h->keys = (khkey_t *)p;                                             \
+    h->vals = (khval_t *)(p+sizeof(khkey_t)*sz);                        \
+    h->ed_flags = (p+sizeof(khkey_t)*sz+sizeof(khval_t)*sz);            \
+    kh_fill_flags(h->ed_flags, 0xaa, sz/4);                             \
     h->mask = sz-1;                                                     \
     h->inc = sz/2-1;                                                    \
   }                                                                     \
@@ -124,24 +124,21 @@ kh_fill_flags(uint8_t *p, uint8_t c, size_t len)
   {                                                                     \
     if (h) {                                                            \
       mrb_free(h->mrb, h->keys);                                        \
-      mrb_free(h->mrb, h->vals);                                        \
-      mrb_free(h->mrb, h->e_flags);                                     \
       mrb_free(h->mrb, h);                                              \
     }                                                                   \
   }                                                                     \
   void kh_clear_##name(kh_##name##_t *h)                                \
   {                                                                     \
-    if (h && h->e_flags) {                                              \
-      kh_fill_flags(h->e_flags, 0xff, h->n_buckets/8);                  \
-      kh_fill_flags(h->d_flags, 0x00, h->n_buckets/8);                  \
+    if (h && h->ed_flags) {                                             \
+      kh_fill_flags(h->ed_flags, 0xaa, h->n_buckets/4);                 \
       h->size = h->n_occupied = 0;                                      \
     }                                                                   \
   }                                                                     \
   khint_t kh_get_##name(kh_##name##_t *h, khkey_t key)                  \
   {                                                                     \
     khint_t k = __hash_func(h->mrb,key) & (h->mask);                    \
-    while (!__ac_isempty(h->e_flags, h->d_flags, k)) {                  \
-      if (!__ac_isdel(h->e_flags, h->d_flags, k)) {                     \
+    while (!__ac_isempty(h->ed_flags, k)) {                             \
+      if (!__ac_isdel(h->ed_flags, k)) {                                \
         if (__hash_equal(h->mrb,h->keys[k], key)) return k;             \
       }                                                                 \
       k = (k+h->inc) & (h->mask);                                       \
@@ -154,7 +151,7 @@ kh_fill_flags(uint8_t *p, uint8_t c, size_t len)
       new_n_buckets = KHASH_MIN_SIZE;                                   \
     khash_power2(new_n_buckets);                                        \
     {                                                                   \
-      uint8_t *old_e_flags = h->e_flags;                                \
+      uint8_t *old_ed_flags = h->ed_flags;                              \
       khkey_t *old_keys = h->keys;                                      \
       khval_t *old_vals = h->vals;                                      \
       khint_t old_n_buckets = h->n_buckets;                             \
@@ -163,14 +160,12 @@ kh_fill_flags(uint8_t *p, uint8_t c, size_t len)
       kh_alloc_##name(h);                                               \
       /* relocate */                                                    \
       for (i=0 ; i<old_n_buckets ; i++) {                               \
-        if (!__ac_isempty(old_e_flags, old_d_flags, i)) {               \
+        if (!__ac_iseither(old_ed_flags, i)) {                          \
           khint_t k = kh_put_##name(h, old_keys[i]);                    \
           kh_value(h,k) = old_vals[i];                                  \
         }                                                               \
       }                                                                 \
-      mrb_free(h->mrb, old_e_flags);                                    \
       mrb_free(h->mrb, old_keys);                                       \
-      mrb_free(h->mrb, old_vals);                                       \
     }                                                                   \
   }                                                                     \
   khint_t kh_put_##name(kh_##name##_t *h, khkey_t key)                  \
@@ -180,27 +175,27 @@ kh_fill_flags(uint8_t *p, uint8_t c, size_t len)
       kh_resize_##name(h, h->n_buckets*2);                              \
     }                                                                   \
     k = __hash_func(h->mrb,key) & (h->mask);                            \
-    while (!__ac_iseither(h->e_flags, h->d_flags, k)) {                 \
+    while (!__ac_iseither(h->ed_flags, k)) {                            \
       if (__hash_equal(h->mrb,h->keys[k], key)) break;                  \
       k = (k+h->inc) & (h->mask);                                       \
     }                                                                   \
-    if (__ac_isempty(h->e_flags, h->d_flags, k)) {                      \
+    if (__ac_isempty(h->ed_flags, k)) {                                 \
       /* put at empty */                                                \
       h->keys[k] = key;                                                 \
-      h->e_flags[k/8] &= ~__m[k%8];                                     \
+      h->ed_flags[k/4] &= ~__m_empty[k%4];                              \
       h->size++;                                                        \
       h->n_occupied++;                                                  \
-    } else if (__ac_isdel(h->e_flags, h->d_flags, k)) {                 \
+    } else if (__ac_isdel(h->ed_flags, k)) {                            \
       /* put at del */                                                  \
       h->keys[k] = key;                                                 \
-      h->d_flags[k/8] &= ~__m[k%8];                                     \
+      h->ed_flags[k/4] &= ~__m_del[k%4];                                \
       h->size++;                                                        \
     }                                                                   \
     return k;                                                           \
   }                                                                     \
   void kh_del_##name(kh_##name##_t *h, khint_t x)                       \
   {                                                                     \
-    h->d_flags[x/8] |= __m[x%8];                                        \
+    h->ed_flags[x/4] |= __m_del[x%4];                                   \
     h->size--;                                                          \
   }                                                                     \
   kh_##name##_t *kh_copy_##name(mrb_state *mrb, kh_##name##_t *h)       \
@@ -231,7 +226,7 @@ kh_fill_flags(uint8_t *p, uint8_t c, size_t len)
 #define kh_del(name, h, k) kh_del_##name(h, k)
 #define kh_copy(name, mrb, h) kh_copy_##name(mrb, h)
 
-#define kh_exist(h, x) (!__ac_iseither((h)->e_flags, (h)->d_flags, (x)))
+#define kh_exist(h, x) (!__ac_iseither((h)->ed_flags, (x)))
 #define kh_key(h, x) ((h)->keys[x])
 #define kh_val(h, x) ((h)->vals[x])
 #define kh_value(h, x) ((h)->vals[x])
diff --git a/include/mruby/string.h b/include/mruby/string.h
index 26d1344d8..000c80b09 100644
--- a/include/mruby/string.h
+++ b/include/mruby/string.h
@@ -57,7 +57,7 @@ mrb_value mrb_str_to_str(mrb_state *mrb, mrb_value str);
 mrb_int mrb_str_hash(mrb_state *mrb, mrb_value str);
 mrb_value mrb_str_buf_append(mrb_state *mrb, mrb_value str, mrb_value str2);
 mrb_value mrb_str_inspect(mrb_state *mrb, mrb_value str);
-int mrb_str_equal(mrb_state *mrb, mrb_value str1, mrb_value str2);
+mrb_bool mrb_str_equal(mrb_state *mrb, mrb_value str1, mrb_value str2);
 mrb_value mrb_str_dump(mrb_state *mrb, mrb_value str);
 mrb_value mrb_str_cat(mrb_state *mrb, mrb_value str, const char *ptr, size_t len);
 mrb_value mrb_str_append(mrb_state *mrb, mrb_value str, mrb_value str2);
diff --git a/include/mruby/value.h b/include/mruby/value.h
index 06241ec76..e78035b5f 100644
--- a/include/mruby/value.h
+++ b/include/mruby/value.h
@@ -51,23 +51,29 @@
 typedef short mrb_sym;
 
 #ifdef _MSC_VER
-# define _ALLOW_KEYWORD_MACROS
-# include <float.h>
-# define inline __inline
+# ifndef __cplusplus
+#  define inline __inline
+# endif
 # define snprintf _snprintf
-# define isnan _isnan
-# define isinf(n) (!_finite(n) && !_isnan(n))
-# define strtoll _strtoi64
-# define PRId32 "I32d"
-# define PRIi32 "I32i"
-# define PRIo32 "I32o"
-# define PRIx32 "I32x"
-# define PRIX32 "I32X"
-# define PRId64 "I64d"
-# define PRIi64 "I64i"
-# define PRIo64 "I64o"
-# define PRIx64 "I64x"
-# define PRIX64 "I64X"
+# if _MSC_VER < 1800
+#  include <float.h>
+#  define isnan _isnan
+#  define isinf(n) (!_finite(n) && !_isnan(n))
+#  define strtoll _strtoi64
+#  define strtof (float)strtod
+#  define PRId32 "I32d"
+#  define PRIi32 "I32i"
+#  define PRIo32 "I32o"
+#  define PRIx32 "I32x"
+#  define PRIX32 "I32X"
+#  define PRId64 "I64d"
+#  define PRIi64 "I64i"
+#  define PRIo64 "I64o"
+#  define PRIx64 "I64x"
+#  define PRIX64 "I64X"
+# else
+#  include <inttypes.h>
+# endif
 #else
 # include <inttypes.h>
 #endif
diff --git a/minirake b/minirake
index f41b9b587..e48ca1306 100755
--- a/minirake
+++ b/minirake
@@ -317,6 +317,8 @@ class RakeApp
       "Require MODULE before executing rakefile."],
     ['--tasks',    '-T', GetoptLong::NO_ARGUMENT,
       "Display the tasks and dependencies, then exit."],
+    ['--pull-gems','-p', GetoptLong::NO_ARGUMENT,
+      "Pull all git mrbgems."],
     ['--trace',    '-t', GetoptLong::NO_ARGUMENT,
       "Turn on invoke/execute tracing."],
     ['--usage',    '-h', GetoptLong::NO_ARGUMENT,
@@ -401,6 +403,8 @@ class RakeApp
       require value
     when '--tasks'
       $show_tasks = true
+    when '--pull-gems'
+      $pull_gems = true
     when '--trace'
       $trace = true
     when '--usage'
@@ -419,6 +423,7 @@ class RakeApp
   # Read and handle the command line options.
   def handle_options
     $verbose = false
+    $pull_gems = false
     opts = GetoptLong.new(*command_line_options)
     opts.each { |opt, value| do_option(opt, value) }
   end
diff --git a/mrbgems/default.gembox b/mrbgems/default.gembox
index 1c6732d48..33ee99be0 100644
--- a/mrbgems/default.gembox
+++ b/mrbgems/default.gembox
@@ -41,12 +41,18 @@ MRuby::GemBox.new do |conf|
   # Use Random class
   conf.gem :core => "mruby-random"
 
+  # Use extensional Object class
+  conf.gem :core => "mruby-object-ext"
+
   # Use ObjectSpace class
   conf.gem :core => "mruby-objectspace"
 
   # Use Fiber class
   conf.gem :core => "mruby-fiber"
 
+  # Use extended toplevel object (main) methods
+  conf.gem :core => "mruby-toplevel-ext"
+
   # Generate mirb command
   conf.gem :core => "mruby-bin-mirb"
 
diff --git a/mrbgems/mruby-array-ext/mrbgem.rake b/mrbgems/mruby-array-ext/mrbgem.rake
index 38e0ad267..18f92ad65 100644
--- a/mrbgems/mruby-array-ext/mrbgem.rake
+++ b/mrbgems/mruby-array-ext/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-array-ext') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-bin-mirb/mrbgem.rake b/mrbgems/mruby-bin-mirb/mrbgem.rake
index fd0b20254..846a3b077 100644
--- a/mrbgems/mruby-bin-mirb/mrbgem.rake
+++ b/mrbgems/mruby-bin-mirb/mrbgem.rake
@@ -1,5 +1,8 @@
 MRuby::Gem::Specification.new('mruby-bin-mirb') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
+
+  spec.linker.libraries << 'readline' if spec.cc.defines.include? "ENABLE_READLINE"
+
   spec.bins = %w(mirb)
 end
diff --git a/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c b/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c
index 5e3e123c6..50556e092 100644
--- a/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c
+++ b/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c
@@ -15,11 +15,19 @@
 #include <mruby/data.h>
 #include <mruby/compile.h>
 #ifdef ENABLE_READLINE
+#include <limits.h>
 #include <readline/readline.h>
 #include <readline/history.h>
 #endif
 #include <mruby/string.h>
 
+
+#ifdef ENABLE_READLINE
+static const char *history_file_name = ".mirb_history";
+char history_path[PATH_MAX];
+#endif
+
+
 static void
 p(mrb_state *mrb, mrb_value obj, int prompt)
 {
@@ -38,7 +46,7 @@ p(mrb_state *mrb, mrb_value obj, int prompt)
 
 /* Guess if the user might want to enter more
  * or if he wants an evaluation of his code now */
-int
+mrb_bool
 is_code_block_open(struct mrb_parser_state *parser)
 {
   int code_block_open = FALSE;
@@ -236,6 +244,8 @@ main(int argc, char **argv)
 #ifndef ENABLE_READLINE
   int last_char;
   int char_index;
+#else
+  char *home = NULL;
 #endif
   mrbc_context *cxt;
   struct mrb_parser_state *parser;
@@ -268,6 +278,23 @@ main(int argc, char **argv)
   if (args.verbose) cxt->dump_result = 1;
 
   ai = mrb_gc_arena_save(mrb);
+
+#ifdef ENABLE_READLINE
+  using_history();
+  home = getenv("HOME");
+#ifdef _WIN32
+  if (!home)
+    home = getenv("USERPROFILE");
+#endif
+  if (home) {
+    strcpy(history_path, home);
+    strcat(history_path, "/");
+    strcat(history_path, history_file_name);
+    read_history(history_path);
+  }
+#endif
+
+
   while (TRUE) {
 #ifndef ENABLE_READLINE
     print_cmdline(code_block_open);
@@ -346,7 +373,7 @@ main(int argc, char **argv)
         }
         else {
           /* no */
-          if (!mrb_respond_to(mrb,result,mrb_intern(mrb,"inspect"))){
+          if (!mrb_respond_to(mrb, result, mrb_intern2(mrb, "inspect", 7))){
             result = mrb_any_to_s(mrb,result);
           }
           p(mrb, result, 1);
@@ -361,5 +388,9 @@ main(int argc, char **argv)
   mrbc_context_free(mrb, cxt);
   mrb_close(mrb);
 
+#ifdef ENABLE_READLINE
+  write_history(history_path);
+#endif
+
   return 0;
 }
diff --git a/mrbgems/mruby-bin-mruby/mrbgem.rake b/mrbgems/mruby-bin-mruby/mrbgem.rake
index 2e173a291..08ba89855 100644
--- a/mrbgems/mruby-bin-mruby/mrbgem.rake
+++ b/mrbgems/mruby-bin-mruby/mrbgem.rake
@@ -1,5 +1,5 @@
 MRuby::Gem::Specification.new('mruby-bin-mruby') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
   spec.bins = %w(mruby)
 end
diff --git a/mrbgems/mruby-enum-ext/mrbgem.rake b/mrbgems/mruby-enum-ext/mrbgem.rake
index 758d298dc..e054f4318 100644
--- a/mrbgems/mruby-enum-ext/mrbgem.rake
+++ b/mrbgems/mruby-enum-ext/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-enum-ext') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-eval/mrbgem.rake b/mrbgems/mruby-eval/mrbgem.rake
index f80cf1b9e..217a9e604 100644
--- a/mrbgems/mruby-eval/mrbgem.rake
+++ b/mrbgems/mruby-eval/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-eval') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-fiber/mrbgem.rake b/mrbgems/mruby-fiber/mrbgem.rake
index cb258adcb..25009c47f 100644
--- a/mrbgems/mruby-fiber/mrbgem.rake
+++ b/mrbgems/mruby-fiber/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-fiber') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-hash-ext/mrbgem.rake b/mrbgems/mruby-hash-ext/mrbgem.rake
index 3163c8c88..25d4f8e61 100644
--- a/mrbgems/mruby-hash-ext/mrbgem.rake
+++ b/mrbgems/mruby-hash-ext/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-hash-ext') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-math/mrbgem.rake b/mrbgems/mruby-math/mrbgem.rake
index 4b0fa40fd..75d3d1fff 100644
--- a/mrbgems/mruby-math/mrbgem.rake
+++ b/mrbgems/mruby-math/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-math') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-math/src/math.c b/mrbgems/mruby-math/src/math.c
index bf3c007b4..bdc7767f7 100644
--- a/mrbgems/mruby-math/src/math.c
+++ b/mrbgems/mruby-math/src/math.c
@@ -12,8 +12,8 @@
 #define domain_error(msg) \
     mrb_raise(mrb, E_RANGE_ERROR, "Numerical argument is out of domain - " #msg)
 
-/* math functions not provided under Microsoft Visual C++ */
-#ifdef _MSC_VER
+/* math functions not provided by Microsoft Visual C++ 2012 or older */
+#if defined _MSC_VER && _MSC_VER < 1800
 
 #define MATH_TOLERANCE 1E-12
 
@@ -87,6 +87,12 @@ erfc(double x)
   return one_sqrtpi*exp(-x*x)*q2;
 }
 
+double
+log2(double x)
+{
+    return log10(x)/log10(2.0);
+}
+
 #endif
 
 /*
@@ -358,18 +364,6 @@ math_atanh(mrb_state *mrb, mrb_value obj)
 # define log10(x) ((x) < 0.0 ? nan("") : log10(x))
 #endif
 
-#ifndef log2
-#ifndef HAVE_LOG2
-double
-log2(double x)
-{
-    return log10(x)/log10(2.0);
-}
-#else
-extern double log2(double);
-#endif
-#endif
-
 /*
  *  call-seq:
  *     Math.exp(x)    -> float
diff --git a/mrbgems/mruby-numeric-ext/mrbgem.rake b/mrbgems/mruby-numeric-ext/mrbgem.rake
index 69c4fde4c..010804058 100644
--- a/mrbgems/mruby-numeric-ext/mrbgem.rake
+++ b/mrbgems/mruby-numeric-ext/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-numeric-ext') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-object-ext/mrbgem.rake b/mrbgems/mruby-object-ext/mrbgem.rake
new file mode 100644
index 000000000..980f1667a
--- /dev/null
+++ b/mrbgems/mruby-object-ext/mrbgem.rake
@@ -0,0 +1,4 @@
+MRuby::Gem::Specification.new('mruby-object-ext') do |spec|
+  spec.license = 'MIT'
+  spec.author  = 'mruby developers'
+end
diff --git a/mrbgems/mruby-object-ext/src/object.c b/mrbgems/mruby-object-ext/src/object.c
new file mode 100644
index 000000000..598ebe91d
--- /dev/null
+++ b/mrbgems/mruby-object-ext/src/object.c
@@ -0,0 +1,108 @@
+#include "mruby.h"
+#include "mruby/array.h"
+#include "mruby/class.h"
+
+/*
+ *  call-seq:
+ *     nil.to_a    -> []
+ *
+ *  Always returns an empty array.
+ */
+
+static mrb_value
+nil_to_a(mrb_state *mrb, mrb_value obj)
+{
+    return mrb_ary_new(mrb);
+}
+
+/*
+ *  call-seq:
+ *     nil.to_f    -> 0.0
+ *
+ *  Always returns zero.
+ */
+
+static mrb_value
+nil_to_f(mrb_state *mrb, mrb_value obj)
+{
+    return mrb_float_value(mrb, 0.0);
+}
+
+/*
+ *  call-seq:
+ *     nil.to_i    -> 0
+ *
+ *  Always returns zero.
+ */
+
+static mrb_value
+nil_to_i(mrb_state *mrb, mrb_value obj)
+{
+    return mrb_fixnum_value(0);
+}
+
+/*
+ *  call-seq:
+ *     obj.instance_exec(arg...) {|var...| block }                       -> obj
+ *
+ *  Executes the given block within the context of the receiver
+ *  (_obj_). In order to set the context, the variable +self+ is set
+ *  to _obj_ while the code is executing, giving the code access to
+ *  _obj_'s instance variables.  Arguments are passed as block parameters.
+ *
+ *     class KlassWithSecret
+ *       def initialize
+ *         @secret = 99
+ *       end
+ *     end
+ *     k = KlassWithSecret.new
+ *     k.instance_exec(5) {|x| @secret+x }   #=> 104
+ */
+
+mrb_value 
+mrb_yield_internal(mrb_state *mrb, mrb_value b, int argc, mrb_value *argv, mrb_value self, struct RClass *c);
+
+static mrb_value
+mrb_obj_instance_exec(mrb_state *mrb, mrb_value self)
+{
+  mrb_value *argv;
+  int argc;
+  mrb_value blk;
+  struct RClass *c;
+  
+  mrb_get_args(mrb, "*&", &argv, &argc, &blk);
+
+  if (mrb_nil_p(blk)) {
+    mrb_raise(mrb, E_ARGUMENT_ERROR, "no block given");
+  }
+
+  switch (mrb_type(self)) {
+  case MRB_TT_SYMBOL:
+  case MRB_TT_FIXNUM:
+  case MRB_TT_FLOAT:
+    c = 0;
+    break;
+  default:
+    c = mrb_class_ptr(mrb_singleton_class(mrb, self));
+    break;
+  }
+
+  return mrb_yield_internal(mrb, blk, argc, argv, self, c);
+}
+
+void
+mrb_mruby_object_ext_gem_init(mrb_state* mrb)
+{
+  struct RClass * n = mrb->nil_class;
+
+  mrb_define_method(mrb, n, "to_a", nil_to_a,       MRB_ARGS_NONE());
+  mrb_define_method(mrb, n, "to_f", nil_to_f,       MRB_ARGS_NONE());
+  mrb_define_method(mrb, n, "to_i", nil_to_i,       MRB_ARGS_NONE());
+
+  mrb_define_method(mrb, mrb->object_class, "instance_exec", mrb_obj_instance_exec, MRB_ARGS_ANY() | MRB_ARGS_BLOCK());
+}
+
+void
+mrb_mruby_object_ext_gem_final(mrb_state* mrb)
+{
+}
diff --git a/mrbgems/mruby-object-ext/test/nil.rb b/mrbgems/mruby-object-ext/test/nil.rb
new file mode 100644
index 000000000..e385dec6a
--- /dev/null
+++ b/mrbgems/mruby-object-ext/test/nil.rb
@@ -0,0 +1,11 @@
+assert('NilClass#to_a') do
+  assert_equal nil.to_a, []
+end
+
+assert('NilClass#to_f') do
+  assert_equal nil.to_f, 0.0
+end
+
+assert('NilClass#to_i') do
+  assert_equal nil.to_i, 0
+end
diff --git a/mrbgems/mruby-object-ext/test/object.rb b/mrbgems/mruby-object-ext/test/object.rb
new file mode 100644
index 000000000..1a75622f6
--- /dev/null
+++ b/mrbgems/mruby-object-ext/test/object.rb
@@ -0,0 +1,9 @@
+assert('Object#instance_exec') do
+  class KlassWithSecret
+    def initialize
+      @secret = 99
+    end
+  end
+  k = KlassWithSecret.new
+  assert_equal k.instance_exec(5) {|x| @secret+x }, 104
+end
diff --git a/mrbgems/mruby-objectspace/mrbgem.rake b/mrbgems/mruby-objectspace/mrbgem.rake
index 100df4cdc..6a6a3e778 100644
--- a/mrbgems/mruby-objectspace/mrbgem.rake
+++ b/mrbgems/mruby-objectspace/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-objectspace') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-print/mrbgem.rake b/mrbgems/mruby-print/mrbgem.rake
index dc7831280..768fc2e18 100644
--- a/mrbgems/mruby-print/mrbgem.rake
+++ b/mrbgems/mruby-print/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-print') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-proc-ext/mrbgem.rake b/mrbgems/mruby-proc-ext/mrbgem.rake
index 7f979431d..b75fceda3 100644
--- a/mrbgems/mruby-proc-ext/mrbgem.rake
+++ b/mrbgems/mruby-proc-ext/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-proc-ext') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-random/mrbgem.rake b/mrbgems/mruby-random/mrbgem.rake
index 38e93e4b1..7ad3c855c 100644
--- a/mrbgems/mruby-random/mrbgem.rake
+++ b/mrbgems/mruby-random/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-random') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-random/src/random.c b/mrbgems/mruby-random/src/random.c
index 13b4fa7a3..1c89ca21d 100644
--- a/mrbgems/mruby-random/src/random.c
+++ b/mrbgems/mruby-random/src/random.c
@@ -11,12 +11,17 @@
 
 #include <time.h>
 
-#define GLOBAL_RAND_SEED_KEY    "$mrb_g_rand_seed"
-#define INSTANCE_RAND_SEED_KEY  "$mrb_i_rand_seed"
-#define MT_STATE_KEY            "$mrb_i_mt_state"
+#define GLOBAL_RAND_SEED_KEY          "$mrb_g_rand_seed"
+#define GLOBAL_RAND_SEED_KEY_CSTR_LEN 16
+
+#define INSTANCE_RAND_SEED_KEY          "$mrb_i_rand_seed"
+#define INSTANCE_RAND_SEED_KEY_CSTR_LEN 16
+
+#define MT_STATE_KEY          "$mrb_i_mt_state"
+#define MT_STATE_KEY_CSTR_LEN 15
 
 static const struct mrb_data_type mt_state_type = {
-    MT_STATE_KEY, mrb_free,
+  MT_STATE_KEY, mrb_free,
 };
 
 static mt_state *mrb_mt_get_context(mrb_state *mrb,  mrb_value self)
@@ -24,7 +29,7 @@ static mt_state *mrb_mt_get_context(mrb_state *mrb,  mrb_value self)
   mt_state *t;
   mrb_value context;
 
-  context = mrb_iv_get(mrb, self, mrb_intern(mrb, MT_STATE_KEY));
+  context = mrb_iv_get(mrb, self, mrb_intern2(mrb, MT_STATE_KEY, MT_STATE_KEY_CSTR_LEN));
   t = (mt_state*)mrb_data_get_ptr(mrb, context, &mt_state_type);
   if (!t)
     mrb_raise(mrb, E_RUNTIME_ERROR, "mt_state get from mrb_iv_get failed");
@@ -141,7 +146,7 @@ static mrb_value mrb_random_g_rand(mrb_state *mrb, mrb_value self)
   mrb_value seed;
 
   max = get_opt(mrb);
-  seed = mrb_gv_get(mrb, mrb_intern(mrb, GLOBAL_RAND_SEED_KEY));
+  seed = mrb_gv_get(mrb, mrb_intern2(mrb, GLOBAL_RAND_SEED_KEY, GLOBAL_RAND_SEED_KEY_CSTR_LEN));
   if (mrb_nil_p(seed)) {
     mrb_random_mt_g_srand(mrb, mrb_nil_value());
   }
@@ -155,8 +160,8 @@ static mrb_value mrb_random_g_srand(mrb_state *mrb, mrb_value self)
 
   seed = get_opt(mrb);
   seed = mrb_random_mt_g_srand(mrb, seed);
-  old_seed = mrb_gv_get(mrb, mrb_intern(mrb, GLOBAL_RAND_SEED_KEY));
-  mrb_gv_set(mrb, mrb_intern(mrb, GLOBAL_RAND_SEED_KEY), seed);
+  old_seed = mrb_gv_get(mrb, mrb_intern2(mrb, GLOBAL_RAND_SEED_KEY, GLOBAL_RAND_SEED_KEY_CSTR_LEN));
+  mrb_gv_set(mrb, mrb_intern2(mrb, GLOBAL_RAND_SEED_KEY, GLOBAL_RAND_SEED_KEY_CSTR_LEN), seed);
   return old_seed;
 }
 
@@ -170,8 +175,8 @@ static mrb_value mrb_random_init(mrb_state *mrb, mrb_value self)
 
   seed = get_opt(mrb);
   seed = mrb_random_mt_srand(mrb, t, seed);
-  mrb_iv_set(mrb, self, mrb_intern(mrb, INSTANCE_RAND_SEED_KEY), seed);
-  mrb_iv_set(mrb, self, mrb_intern(mrb, MT_STATE_KEY),
+  mrb_iv_set(mrb, self, mrb_intern2(mrb, INSTANCE_RAND_SEED_KEY, INSTANCE_RAND_SEED_KEY_CSTR_LEN), seed);
+  mrb_iv_set(mrb, self, mrb_intern2(mrb, MT_STATE_KEY, MT_STATE_KEY_CSTR_LEN),
     mrb_obj_value(Data_Wrap_Struct(mrb, mrb->object_class, &mt_state_type, (void*) t)));
   return self;
 }
@@ -183,7 +188,7 @@ static mrb_value mrb_random_rand(mrb_state *mrb, mrb_value self)
   mt_state *t = mrb_mt_get_context(mrb, self);
 
   max = get_opt(mrb);
-  seed = mrb_iv_get(mrb, self, mrb_intern(mrb, INSTANCE_RAND_SEED_KEY));
+  seed = mrb_iv_get(mrb, self, mrb_intern2(mrb, INSTANCE_RAND_SEED_KEY, INSTANCE_RAND_SEED_KEY_CSTR_LEN));
   if (mrb_nil_p(seed)) {
     mrb_random_mt_srand(mrb, t, mrb_nil_value());
   }
@@ -198,8 +203,8 @@ static mrb_value mrb_random_srand(mrb_state *mrb, mrb_value self)
 
   seed = get_opt(mrb);
   seed = mrb_random_mt_srand(mrb, t, seed);
-  old_seed = mrb_iv_get(mrb, self, mrb_intern(mrb, INSTANCE_RAND_SEED_KEY));
-  mrb_iv_set(mrb, self, mrb_intern(mrb, INSTANCE_RAND_SEED_KEY), seed);
+  old_seed = mrb_iv_get(mrb, self, mrb_intern2(mrb, INSTANCE_RAND_SEED_KEY, INSTANCE_RAND_SEED_KEY_CSTR_LEN));
+  mrb_iv_set(mrb, self, mrb_intern2(mrb, INSTANCE_RAND_SEED_KEY, INSTANCE_RAND_SEED_KEY_CSTR_LEN), seed);
 
   return old_seed;
 }
diff --git a/mrbgems/mruby-range-ext/mrbgem.rake b/mrbgems/mruby-range-ext/mrbgem.rake
index 5ed521a44..a7970aa51 100644
--- a/mrbgems/mruby-range-ext/mrbgem.rake
+++ b/mrbgems/mruby-range-ext/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-range-ext') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-range-ext/src/range.c b/mrbgems/mruby-range-ext/src/range.c
index 377677ffb..4e17dac8c 100644
--- a/mrbgems/mruby-range-ext/src/range.c
+++ b/mrbgems/mruby-range-ext/src/range.c
@@ -1,7 +1,7 @@
 #include "mruby.h"
 #include "mruby/range.h"
 
-static int
+static mrb_bool
 r_le(mrb_state *mrb, mrb_value a, mrb_value b)
 {
   mrb_value r = mrb_funcall(mrb, a, "<=>", 1, b); /* compare result */
@@ -15,7 +15,7 @@ r_le(mrb_state *mrb, mrb_value a, mrb_value b)
   return FALSE;
 }
 
-static int
+static mrb_bool
 r_lt(mrb_state *mrb, mrb_value a, mrb_value b)
 {
   mrb_value r = mrb_funcall(mrb, a, "<=>", 1, b);
diff --git a/mrbgems/mruby-sprintf/mrbgem.rake b/mrbgems/mruby-sprintf/mrbgem.rake
index 8772a5174..3e15ee7a9 100644
--- a/mrbgems/mruby-sprintf/mrbgem.rake
+++ b/mrbgems/mruby-sprintf/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-sprintf') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-sprintf/src/sprintf.c b/mrbgems/mruby-sprintf/src/sprintf.c
index 55698d09f..6479b19bc 100644
--- a/mrbgems/mruby-sprintf/src/sprintf.c
+++ b/mrbgems/mruby-sprintf/src/sprintf.c
@@ -15,10 +15,6 @@
 #include <math.h>
 #include <ctype.h>
 
-#ifdef _MSC_VER
-#include <float.h>
-#endif
-
 #ifdef HAVE_IEEEFP_H
 #include <ieeefp.h>
 #endif
diff --git a/mrbgems/mruby-string-ext/mrbgem.rake b/mrbgems/mruby-string-ext/mrbgem.rake
index 83db97eb4..4a3369998 100644
--- a/mrbgems/mruby-string-ext/mrbgem.rake
+++ b/mrbgems/mruby-string-ext/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-string-ext') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-struct/mrbgem.rake b/mrbgems/mruby-struct/mrbgem.rake
index 476e990da..3e9eab8d7 100644
--- a/mrbgems/mruby-struct/mrbgem.rake
+++ b/mrbgems/mruby-struct/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-struct') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-struct/src/struct.c b/mrbgems/mruby-struct/src/struct.c
index a2731ca54..a8511fc3c 100644
--- a/mrbgems/mruby-struct/src/struct.c
+++ b/mrbgems/mruby-struct/src/struct.c
@@ -43,7 +43,7 @@ struct_ivar_get(mrb_state *mrb, mrb_value c, mrb_sym id)
 mrb_value
 mrb_struct_iv_get(mrb_state *mrb, mrb_value c, const char *name)
 {
-  return struct_ivar_get(mrb, c, mrb_intern(mrb, name));
+  return struct_ivar_get(mrb, c, mrb_intern_cstr(mrb, name));
 }
 
 mrb_value
@@ -185,8 +185,7 @@ static mrb_value
 mrb_struct_set(mrb_state *mrb, mrb_value obj, mrb_value val)
 {
   const char *name;
-  int i;
-  size_t len;
+  size_t i, len;
   mrb_sym mid;
   mrb_value members, slot, *ptr, *ptr_members;
 
diff --git a/mrbgems/mruby-symbol-ext/mrbgem.rake b/mrbgems/mruby-symbol-ext/mrbgem.rake
index 8e40c743b..6294e7a46 100644
--- a/mrbgems/mruby-symbol-ext/mrbgem.rake
+++ b/mrbgems/mruby-symbol-ext/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-symbol-ext') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-time/mrbgem.rake b/mrbgems/mruby-time/mrbgem.rake
index 0f0b4899d..edf2aa3fc 100644
--- a/mrbgems/mruby-time/mrbgem.rake
+++ b/mrbgems/mruby-time/mrbgem.rake
@@ -1,4 +1,4 @@
 MRuby::Gem::Specification.new('mruby-time') do |spec|
   spec.license = 'MIT'
-  spec.authors = 'mruby developers'
+  spec.author  = 'mruby developers'
 end
diff --git a/mrbgems/mruby-time/src/time.c b/mrbgems/mruby-time/src/time.c
index 2a2aabe72..8b797f047 100644
--- a/mrbgems/mruby-time/src/time.c
+++ b/mrbgems/mruby-time/src/time.c
@@ -105,7 +105,7 @@ static const char *mon_names[] = {
 };
 
 static const char *wday_names[] = {
-  "Sun", "Mon", "Tus", "Wed", "Thu", "Fri", "Sat",
+  "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat",
 };
 
 struct mrb_time {
diff --git a/mrbgems/mruby-toplevel-ext/mrbgem.rake b/mrbgems/mruby-toplevel-ext/mrbgem.rake
new file mode 100644
index 000000000..78eb73a26
--- /dev/null
+++ b/mrbgems/mruby-toplevel-ext/mrbgem.rake
@@ -0,0 +1,4 @@
+MRuby::Gem::Specification.new('mruby-toplevel-ext') do |spec|
+  spec.license = 'MIT'
+  spec.author  = 'mruby developers'
+end
diff --git a/mrbgems/mruby-toplevel-ext/mrblib/toplevel.rb b/mrbgems/mruby-toplevel-ext/mrblib/toplevel.rb
new file mode 100644
index 000000000..774562398
--- /dev/null
+++ b/mrbgems/mruby-toplevel-ext/mrblib/toplevel.rb
@@ -0,0 +1,11 @@
+
+def self.include (*modules)
+  self.class.include(*modules)
+end
+
+def self.private(*methods)
+end
+def self.protected(*methods)
+end
+def self.public(*methods)
+end
diff --git a/mrbgems/mruby-toplevel-ext/test/toplevel.rb b/mrbgems/mruby-toplevel-ext/test/toplevel.rb
new file mode 100644
index 000000000..4401beba1
--- /dev/null
+++ b/mrbgems/mruby-toplevel-ext/test/toplevel.rb
@@ -0,0 +1,24 @@
+##
+# Toplevel Self(Ext) Test
+
+module ToplevelTestModule1
+  def method_foo
+    :foo
+  end
+
+  CONST_BAR = :bar
+end
+
+module ToplevelTestModule2
+  CONST_BAR = :bar2
+end
+
+assert('Toplevel#include') do
+  self.include ToplevelTestModule2, ToplevelTestModule1
+  
+  assert_true self.class.included_modules.include?( ToplevelTestModule1 )
+  assert_true self.class.included_modules.include?( ToplevelTestModule2 )
+  assert_equal :foo, method_foo
+  assert_equal :bar2, CONST_BAR
+end
+
diff --git a/mrblib/class.rb b/mrblib/class.rb
index 4f268b6c8..6d624ee83 100644
--- a/mrblib/class.rb
+++ b/mrblib/class.rb
@@ -1,18 +1,24 @@
 class Module
   # 15.2.2.4.13
   def attr_reader(*names)
-    names.each{|name|
-      name2 = ('@'+name.to_s).intern
-      define_method(name){self.instance_variable_get(name2)}
-    }
+    names.each do |name|
+      name = name.to_s
+      raise(NameError, "#{name.inspect} is not allowed as an instance variable name") if name.include?('@') || name.include?('?')  || name.include?('$')
+      
+      attr_name = '@'+name
+      define_method(name){self.instance_variable_get(attr_name)}
+    end
   end
   # 15.2.2.4.14
   def attr_writer(*names)
-    names.each{|name|
-      name2 = ('@'+name.to_s).intern
-      name = (name.to_s+"=").intern
-      define_method(name){|v|self.instance_variable_set(name2,v)}
-    }
+    names.each do |name|
+      name = name.to_s
+      raise(NameError, "#{name.inspect} is not allowed as an instance variable name") if name.include?('@') || name.include?('?')  || name.include?('$')
+      
+      attr_name = '@'+name
+      name = (name+"=").intern
+      define_method(name){|v|self.instance_variable_set(attr_name,v)}
+    end
   end
   # 15.2.2.4.12
   def attr_accessor(*names)
diff --git a/mrblib/string.rb b/mrblib/string.rb
index 131d30446..49f87be8b 100644
--- a/mrblib/string.rb
+++ b/mrblib/string.rb
@@ -133,6 +133,18 @@ class String
     a = self[pos+1..-1]
     self.replace([b, value, a].join(''))
   end
+
+  ##
+  # ISO 15.2.10.5.5
+  def =~(re)
+    re =~ self
+  end
+
+  ##
+  # ISO 15.2.10.5.27
+  def match(re, &block)
+    re.match(self, &block)
+  end
 end
 
 ##
diff --git a/src/array.c b/src/array.c
index a4a09ec0a..ceda884c0 100644
--- a/src/array.c
+++ b/src/array.c
@@ -19,7 +19,7 @@
 #define ARY_DEFAULT_LEN   4
 #define ARY_SHRINK_RATIO  5 /* must be larger than 2 */
 #define ARY_C_MAX_SIZE (SIZE_MAX / sizeof(mrb_value))
-#define ARY_MAX_SIZE ((ARY_C_MAX_SIZE < (size_t)MRB_INT_MAX) ? (mrb_int)ARY_C_MAX_SIZE : MRB_INT_MAX)
+#define ARY_MAX_SIZE ((ARY_C_MAX_SIZE < (size_t)MRB_INT_MAX) ? (mrb_int)ARY_C_MAX_SIZE : MRB_INT_MAX-1)
 
 static inline mrb_value
 ary_elt(mrb_value ary, mrb_int offset)
@@ -40,7 +40,7 @@ ary_new_capa(mrb_state *mrb, mrb_int capa)
   if (capa > ARY_MAX_SIZE) {
     mrb_raise(mrb, E_ARGUMENT_ERROR, "array size too big");
   }
-  blen = capa * sizeof(mrb_value) ;
+  blen = capa * sizeof(mrb_value);
   if (blen < capa) {
     mrb_raise(mrb, E_ARGUMENT_ERROR, "array size too big");
   }
@@ -926,7 +926,8 @@ inspect_ary(mrb_state *mrb, mrb_value ary, mrb_value list)
     }
     if (mrb_array_p(RARRAY_PTR(ary)[i])) {
       s = inspect_ary(mrb, RARRAY_PTR(ary)[i], list);
-    } else {
+    }
+    else {
       s = mrb_inspect(mrb, RARRAY_PTR(ary)[i]);
     }
     mrb_str_buf_cat(mrb, arystr, RSTRING_PTR(s), RSTRING_LEN(s));
@@ -1056,39 +1057,26 @@ static mrb_value
 mrb_ary_equal(mrb_state *mrb, mrb_value ary1)
 {
   mrb_value ary2;
-  mrb_bool equal_p;
+  mrb_int i;
 
   mrb_get_args(mrb, "o", &ary2);
-  if (mrb_obj_equal(mrb, ary1, ary2)) {
-    equal_p = 1;
-  }
-  else if (mrb_special_const_p(ary2)) {
-    equal_p = 0;
-  }
-  else if (!mrb_array_p(ary2)) {
+  if (mrb_obj_equal(mrb, ary1, ary2)) return mrb_true_value();
+  if (mrb_special_const_p(ary2)) return mrb_false_value();
+  if (!mrb_array_p(ary2)) {
     if (!mrb_respond_to(mrb, ary2, mrb_intern2(mrb, "to_ary", 6))) {
-        equal_p = 0;
+      return mrb_false_value();
     }
     else {
-      equal_p = mrb_equal(mrb, ary2, ary1);
+      return mrb_bool_value(mrb_equal(mrb, ary2, ary1));
     }
   }
-  else if (RARRAY_LEN(ary1) != RARRAY_LEN(ary2)) {
-    equal_p = 0;
-  }
-  else {
-    mrb_int i;
-
-    equal_p = 1;
-    for (i=0; i<RARRAY_LEN(ary1); i++) {
-      if (!mrb_equal(mrb, ary_elt(ary1, i), ary_elt(ary2, i))) {
-        equal_p = 0;
-        break;
-      }
+  if (RARRAY_LEN(ary1) != RARRAY_LEN(ary2)) return mrb_false_value();
+  for (i=0; i<RARRAY_LEN(ary1); i++) {
+    if (!mrb_equal(mrb, ary_elt(ary1, i), ary_elt(ary2, i))) {
+      return mrb_false_value();
     }
   }
-
-  return mrb_bool_value(equal_p);
+  return mrb_true_value();
 }
 
 /* 15.2.12.5.34 (x) */
@@ -1104,30 +1092,18 @@ static mrb_value
 mrb_ary_eql(mrb_state *mrb, mrb_value ary1)
 {
   mrb_value ary2;
-  mrb_bool eql_p;
+  mrb_int i;
 
   mrb_get_args(mrb, "o", &ary2);
-  if (mrb_obj_equal(mrb, ary1, ary2)) {
-    eql_p = 1;
-  }
-  else if (!mrb_array_p(ary2)) {
-    eql_p = 0;
-  }
-  else if (RARRAY_LEN(ary1) != RARRAY_LEN(ary2)) {
-    eql_p = 0;
-  }
-  else {
-    mrb_int i;
-    eql_p = 1;
-    for (i=0; i<RARRAY_LEN(ary1); i++) {
-      if (!mrb_eql(mrb, ary_elt(ary1, i), ary_elt(ary2, i))) {
-        eql_p = 0;
-        break;
-      }
+  if (mrb_obj_equal(mrb, ary1, ary2)) return mrb_true_value();
+  if (!mrb_array_p(ary2)) return mrb_false_value();
+  if (RARRAY_LEN(ary1) != RARRAY_LEN(ary2)) return mrb_false_value();
+  for (i=0; i<RARRAY_LEN(ary1); i++) {
+    if (!mrb_eql(mrb, ary_elt(ary1, i), ary_elt(ary2, i))) {
+      return mrb_false_value();
     }
   }
-
-  return mrb_bool_value(eql_p);
+  return mrb_true_value();
 }
 
 void
diff --git a/src/backtrace.c b/src/backtrace.c
index d5d0818ae..e05ad4326 100644
--- a/src/backtrace.c
+++ b/src/backtrace.c
@@ -18,7 +18,7 @@ mrb_print_backtrace(mrb_state *mrb)
   int i, line;
 
   fputs("trace:\n", stderr);
-  ciidx = mrb_fixnum(mrb_obj_iv_get(mrb, mrb->exc, mrb_intern(mrb, "ciidx")));
+  ciidx = mrb_fixnum(mrb_obj_iv_get(mrb, mrb->exc, mrb_intern2(mrb, "ciidx", 5)));
   if (ciidx >= mrb->c->ciend - mrb->c->cibase)
     ciidx = 10; /* ciidx is broken... */
 
@@ -41,7 +41,7 @@ mrb_print_backtrace(mrb_state *mrb)
           pc = mrb->c->cibase[i+1].pc;
         }
         else {
-          pc = (mrb_code*)mrb_voidp(mrb_obj_iv_get(mrb, mrb->exc, mrb_intern(mrb, "lastpc")));
+          pc = (mrb_code*)mrb_voidp(mrb_obj_iv_get(mrb, mrb->exc, mrb_intern2(mrb, "lastpc", 6)));
         }
         if (irep->iseq <= pc && pc < irep->iseq + irep->ilen) {
           line = irep->lines[pc - irep->iseq - 1];
diff --git a/src/class.c b/src/class.c
index 5fd3a4006..d67a4af3e 100644
--- a/src/class.c
+++ b/src/class.c
@@ -55,7 +55,7 @@ mrb_name_class(mrb_state *mrb, struct RClass *c, mrb_sym name)
   mrb_obj_iv_set(mrb, (struct RObject*)c,
                  mrb_intern2(mrb, "__classid__", 11), mrb_symbol_value(name));
 }
-
+                                
 #define make_metaclass(mrb, c) prepare_singleton_class((mrb), (struct RBasic*)(c))
 
 static void
@@ -78,6 +78,8 @@ prepare_singleton_class(mrb_state *mrb, struct RBasic *o)
   }
   else if (o->tt == MRB_TT_SCLASS) {
     c = (struct RClass*)o;
+    while (c->super->tt == MRB_TT_ICLASS)
+      c = c->super;
     make_metaclass(mrb, c->super);
     sc->super = c->super->c;
   }
@@ -105,7 +107,7 @@ mrb_define_module_id(mrb_state *mrb, mrb_sym name)
 struct RClass*
 mrb_define_module(mrb_state *mrb, const char *name)
 {
-  return mrb_define_module_id(mrb, mrb_intern(mrb, name));
+  return mrb_define_module_id(mrb, mrb_intern_cstr(mrb, name));
 }
 
 static void
@@ -159,9 +161,7 @@ mrb_define_class_id(mrb_state *mrb, mrb_sym name, struct RClass *super)
 struct RClass*
 mrb_define_class(mrb_state *mrb, const char *name, struct RClass *super)
 {
-  struct RClass *c;
-  c = mrb_define_class_id(mrb, mrb_intern(mrb, name), super);
-  return c;
+  return mrb_define_class_id(mrb, mrb_intern_cstr(mrb, name), super);
 }
 
 struct RClass*
@@ -203,7 +203,7 @@ mrb_vm_define_class(mrb_state *mrb, mrb_value outer, mrb_value super, mrb_sym id
   return c;
 }
 
-int
+mrb_bool
 mrb_class_defined(mrb_state *mrb, const char *name)
 {
   mrb_value sym = mrb_check_intern_cstr(mrb, name);
@@ -227,7 +227,13 @@ class_from_sym(mrb_state *mrb, struct RClass *klass, mrb_sym id)
 struct RClass *
 mrb_class_get(mrb_state *mrb, const char *name)
 {
-  return class_from_sym(mrb, mrb->object_class, mrb_intern(mrb, name));
+  return mrb_class_get_under(mrb, mrb->object_class, name);
+}
+
+struct RClass *
+mrb_class_get_under(mrb_state *mrb, struct RClass *outer, const char *name)
+{
+  return class_from_sym(mrb, outer, mrb_intern_cstr(mrb, name));
 }
 
 /*!
@@ -250,7 +256,7 @@ struct RClass *
 mrb_define_class_under(mrb_state *mrb, struct RClass *outer, const char *name, struct RClass *super)
 {
   struct RClass * c;
-  mrb_sym id = mrb_intern(mrb, name);
+  mrb_sym id = mrb_intern_cstr(mrb, name);
 
   if (mrb_const_defined_at(mrb, outer, id)) {
     c = class_from_sym(mrb, outer, id);
@@ -272,7 +278,7 @@ struct RClass *
 mrb_define_module_under(mrb_state *mrb, struct RClass *outer, const char *name)
 {
   struct RClass * c;
-  mrb_sym id = mrb_intern(mrb, name);
+  mrb_sym id = mrb_intern_cstr(mrb, name);
 
   if (mrb_const_defined_at(mrb, outer, id)) {
     c = class_from_sym(mrb, outer, id);
@@ -313,7 +319,7 @@ mrb_define_method_id(mrb_state *mrb, struct RClass *c, mrb_sym mid, mrb_func_t f
 void
 mrb_define_method(mrb_state *mrb, struct RClass *c, const char *name, mrb_func_t func, mrb_aspec aspec)
 {
-  mrb_define_method_id(mrb, c, mrb_intern(mrb, name), func, aspec);
+  mrb_define_method_id(mrb, c, mrb_intern_cstr(mrb, name), func, aspec);
 }
 
 void
@@ -371,20 +377,22 @@ to_hash(mrb_state *mrb, mrb_value val)
 
   format specifiers:
 
-   o: Object [mrb_value]
-   S: String [mrb_value]
-   A: Array [mrb_value]
-   H: Hash [mrb_value]
-   s: String [char*,int]
-   z: String [char*]
-   a: Array [mrb_value*,mrb_int]
-   f: Float [mrb_float]
-   i: Integer [mrb_int]
-   b: Boolean [mrb_bool]
-   n: Symbol [mrb_sym]
-   &: Block [mrb_value]
-   *: rest argument [mrb_value*,int]
-   |: optional
+    string  mruby type     C type                 note
+    ----------------------------------------------------------------------------------------------
+    o:      Object         [mrb_value]
+    S:      String         [mrb_value]
+    A:      Array          [mrb_value]
+    H:      Hash           [mrb_value]
+    s:      String         [char*,int]            Receive two arguments.
+    z:      String         [char*]                NUL terminated string.
+    a:      Array          [mrb_value*,mrb_int]   Receive two arguments.
+    f:      Float          [mrb_float]
+    i:      Integer        [mrb_int]
+    b:      Boolean        [mrb_bool]
+    n:      Symbol         [mrb_sym]
+    &:      Block          [mrb_value]
+    *:      rest argument  [mrb_value*,int]       Receive the rest of the arguments as an array.
+    |:      optional                              Next argument of '|' and later are optional.
  */
 int
 mrb_get_args(mrb_state *mrb, const char *format, ...)
@@ -487,7 +495,7 @@ mrb_get_args(mrb_state *mrb, const char *format, ...)
         if (i < argc) {
           ss = to_str(mrb, *sp++);
           s = mrb_str_ptr(ss);
-          if (strlen(s->ptr) != s->len) {
+          if (strlen(s->ptr) < s->len) {
             mrb_raise(mrb, E_ARGUMENT_ERROR, "String contains NUL");
           }
           *ps = s->ptr;
@@ -903,6 +911,12 @@ mrb_mod_module_eval(mrb_state *mrb, mrb_value mod)
 }
 
 mrb_value
+mrb_mod_dummy_visibility(mrb_state *mrb, mrb_value mod)
+{
+  return mod;
+}
+
+mrb_value
 mrb_singleton_class(mrb_state *mrb, mrb_value v)
 {
   struct RBasic *obj;
@@ -933,7 +947,7 @@ void
 mrb_define_singleton_method(mrb_state *mrb, struct RObject *o, const char *name, mrb_func_t func, mrb_aspec aspec)
 {
   prepare_singleton_class(mrb, (struct RBasic*)o);
-  mrb_define_method_id(mrb, o->c, mrb_intern(mrb, name), func, aspec);
+  mrb_define_method_id(mrb, o->c, mrb_intern_cstr(mrb, name), func, aspec);
 }
 
 void
@@ -1069,6 +1083,7 @@ mrb_class_new_class(mrb_state *mrb, mrb_value cv)
     super = mrb_obj_value(mrb->object_class);
   }
   new_class = mrb_class_new(mrb, mrb_class_ptr(super));
+  mrb_funcall(mrb, super, "inherited", 1, mrb_obj_value(new_class));
   return mrb_obj_value(new_class);
 }
 
@@ -1134,16 +1149,14 @@ mrb_bob_not(mrb_state *mrb, mrb_value cv)
 static mrb_value
 mrb_bob_missing(mrb_state *mrb, mrb_value mod)
 {
-  mrb_value name, *a;
+  mrb_sym name;
+  mrb_value *a;
   int alen;
   mrb_value inspect;
 
-  mrb_get_args(mrb, "o*", &name, &a, &alen);
-  if (!mrb_symbol_p(name)) {
-    mrb_raise(mrb, E_TYPE_ERROR, "name should be a symbol");
-  }
+  mrb_get_args(mrb, "n*", &name, &a, &alen);
 
-  if (mrb_respond_to(mrb,mod,mrb_intern2(mrb,"inspect",7))){
+  if (mrb_respond_to(mrb,mod,mrb_intern2(mrb, "inspect",7))){
     inspect = mrb_funcall(mrb, mod, "inspect", 0);
     if (RSTRING_LEN(inspect) > 64) {
       inspect = mrb_any_to_s(mrb, mod);
@@ -1154,12 +1167,12 @@ mrb_bob_missing(mrb_state *mrb, mrb_value mod)
   }
 
   mrb_raisef(mrb, E_NOMETHOD_ERROR, "undefined method '%S' for %S",
-             mrb_sym2str(mrb, mrb_symbol(name)), inspect);
+             mrb_sym2str(mrb, name), inspect);
   /* not reached */
   return mrb_nil_value();
 }
 
-int
+mrb_bool
 mrb_obj_respond_to(struct RClass* c, mrb_sym mid)
 {
   khiter_t k;
@@ -1183,7 +1196,7 @@ mrb_obj_respond_to(struct RClass* c, mrb_sym mid)
   return FALSE;         /* no method */
 }
 
-int
+mrb_bool
 mrb_respond_to(mrb_state *mrb, mrb_value obj, mrb_sym mid)
 {
   return mrb_obj_respond_to(mrb_class(mrb, obj), mid);
@@ -1338,7 +1351,7 @@ mrb_alias_method(mrb_state *mrb, struct RClass *c, mrb_sym a, mrb_sym b)
 void
 mrb_define_alias(mrb_state *mrb, struct RClass *klass, const char *name1, const char *name2)
 {
-  mrb_alias_method(mrb, klass, mrb_intern(mrb, name1), mrb_intern(mrb, name2));
+  mrb_alias_method(mrb, klass, mrb_intern_cstr(mrb, name1), mrb_intern_cstr(mrb, name2));
 }
 
 /*
@@ -1410,10 +1423,10 @@ mrb_value
 mrb_mod_alias(mrb_state *mrb, mrb_value mod)
 {
   struct RClass *c = mrb_class_ptr(mod);
-  mrb_value new_value, old_value;
+  mrb_sym new_name, old_name;
 
-  mrb_get_args(mrb, "oo", &new_value, &old_value);
-  mrb_alias_method(mrb, c, mrb_symbol(new_value), mrb_symbol(old_value));
+  mrb_get_args(mrb, "nn", &new_name, &old_name);
+  mrb_alias_method(mrb, c, new_name, old_name);
   return mrb_nil_value();
 }
 
@@ -1424,7 +1437,8 @@ undef_method(mrb_state *mrb, struct RClass *c, mrb_sym a)
 
   if (!mrb_obj_respond_to(c, a)) {
     mrb_name_error(mrb, a, "undefined method '%S' for class '%S'", mrb_sym2str(mrb, a), mrb_obj_value(c));
-  } else {
+  }
+  else {
     MRB_SET_VALUE(m, MRB_TT_PROC, value.p, 0);
     mrb_define_method_vm(mrb, c, a, m);
   }
@@ -1433,7 +1447,7 @@ undef_method(mrb_state *mrb, struct RClass *c, mrb_sym a)
 void
 mrb_undef_method(mrb_state *mrb, struct RClass *c, const char *name)
 {
-  undef_method(mrb, c, mrb_intern(mrb, name));
+  undef_method(mrb, c, mrb_intern_cstr(mrb, name));
 }
 
 void
@@ -1506,7 +1520,8 @@ get_sym_or_str_arg(mrb_state *mrb)
 
   if (mrb_symbol_p(sym_or_str) || mrb_string_p(sym_or_str)) {
     return sym_or_str;
-  } else {
+  }
+  else {
     mrb_value obj = mrb_funcall(mrb, sym_or_str, "inspect", 0);
     mrb_raisef(mrb, E_TYPE_ERROR, "%S is not a symbol", obj);
     return mrb_nil_value();
@@ -1538,7 +1553,8 @@ mrb_mod_cvar_defined(mrb_state *mrb, mrb_value mod)
   if (mrb_symbol_p(id)) {
     check_cv_name_sym(mrb, mrb_symbol(id));
     defined_p = mrb_cv_defined(mrb, mod, mrb_symbol(id));
-  } else {
+  }
+  else {
     mrb_value sym;
     check_cv_name_str(mrb, id);
     sym = mrb_check_intern_str(mrb, id);
@@ -1690,7 +1706,8 @@ mrb_mod_method_defined(mrb_state *mrb, mrb_value mod)
   id = get_sym_or_str_arg(mrb);
   if (mrb_symbol_p(id)) {
     method_defined_p = mrb_obj_respond_to(mrb_class_ptr(mod), mrb_symbol(id));
-  } else {
+  }
+  else {
     mrb_value sym = mrb_check_intern_str(mrb, id);
     if (mrb_nil_p(sym)) {
       method_defined_p = FALSE;
@@ -1774,7 +1791,8 @@ mrb_mod_const_defined(mrb_state *mrb, mrb_value mod)
   if (mrb_type(id) == MRB_TT_SYMBOL) {
     check_const_name_sym(mrb, mrb_symbol(id));
     const_defined_p = mrb_const_defined(mrb, mod, mrb_symbol(id));
-  } else {
+  }
+  else {
     mrb_value sym;
     check_const_name_str(mrb, id);
     sym = mrb_check_intern_str(mrb, id);
@@ -1874,10 +1892,10 @@ mrb_init_class(mrb_state *mrb)
   mrb_define_const(mrb, obj, "Class",       mrb_obj_value(cls));
 
   /* name each classes */
-  mrb_name_class(mrb, bob, mrb_intern(mrb, "BasicObject"));
-  mrb_name_class(mrb, obj, mrb_intern(mrb, "Object"));          /* 15.2.1 */
-  mrb_name_class(mrb, mod, mrb_intern(mrb, "Module"));          /* 15.2.2 */
-  mrb_name_class(mrb, cls, mrb_intern(mrb, "Class"));           /* 15.2.3 */
+  mrb_name_class(mrb, bob, mrb_intern2(mrb, "BasicObject", 11)); /* 15.2.1 */
+  mrb_name_class(mrb, obj, mrb_intern2(mrb, "Object", 6));       /* 15.2.1 */
+  mrb_name_class(mrb, mod, mrb_intern2(mrb, "Module", 6));       /* 15.2.2 */
+  mrb_name_class(mrb, cls, mrb_intern2(mrb, "Class", 5));        /* 15.2.3 */
 
   MRB_SET_INSTANCE_TT(cls, MRB_TT_CLASS);
   mrb_define_method(mrb, bob, "initialize",              mrb_bob_init,             MRB_ARGS_NONE());
@@ -1904,6 +1922,9 @@ mrb_init_class(mrb_state *mrb)
   mrb_define_method(mrb, mod, "instance_methods",        mrb_mod_instance_methods, MRB_ARGS_ANY());  /* 15.2.2.4.33 */
   mrb_define_method(mrb, mod, "method_defined?",         mrb_mod_method_defined,   MRB_ARGS_REQ(1)); /* 15.2.2.4.34 */
   mrb_define_method(mrb, mod, "module_eval",             mrb_mod_module_eval,      MRB_ARGS_ANY());  /* 15.2.2.4.35 */
+  mrb_define_method(mrb, mod, "private",                 mrb_mod_dummy_visibility, MRB_ARGS_ANY());  /* 15.2.2.4.36 */
+  mrb_define_method(mrb, mod, "protected",               mrb_mod_dummy_visibility, MRB_ARGS_ANY());  /* 15.2.2.4.37 */
+  mrb_define_method(mrb, mod, "public",                  mrb_mod_dummy_visibility, MRB_ARGS_ANY());  /* 15.2.2.4.38 */
   mrb_define_method(mrb, mod, "remove_class_variable",   mrb_mod_remove_cvar,      MRB_ARGS_REQ(1)); /* 15.2.2.4.39 */
   mrb_define_method(mrb, mod, "remove_method",           mrb_mod_remove_method,    MRB_ARGS_ANY());  /* 15.2.2.4.41 */
   mrb_define_method(mrb, mod, "to_s",                    mrb_mod_to_s,             MRB_ARGS_NONE());
diff --git a/src/codegen.c b/src/codegen.c
index cfbbe7286..5681ce03a 100644
--- a/src/codegen.c
+++ b/src/codegen.c
@@ -59,7 +59,7 @@ typedef struct scope {
   int icapa;
 
   mrb_irep *irep;
-  int pcapa;
+  size_t pcapa;
   int scapa;
 
   int nlocals;
@@ -426,9 +426,8 @@ push_(codegen_scope *s)
 static inline int
 new_lit(codegen_scope *s, mrb_value val)
 {
-  int i;
+  size_t i;
 
-  
   switch (mrb_type(val)) {
   case MRB_TT_STRING:
     for (i=0; i<s->irep->plen; i++) {
@@ -448,7 +447,7 @@ new_lit(codegen_scope *s, mrb_value val)
     }
     break;
   }
-    
+
   if (s->irep->plen == s->pcapa) {
     s->pcapa *= 2;
     s->irep->pool = (mrb_value *)codegen_realloc(s, s->irep->pool, sizeof(mrb_value)*s->pcapa);
@@ -462,7 +461,7 @@ new_lit(codegen_scope *s, mrb_value val)
 static inline int
 new_msym(codegen_scope *s, mrb_sym sym)
 {
-  int i, len;
+  size_t i, len;
 
   len = s->irep->slen;
   if (len > 256) len = 256;
@@ -481,7 +480,7 @@ new_msym(codegen_scope *s, mrb_sym sym)
 static inline int
 new_sym(codegen_scope *s, mrb_sym sym)
 {
-  int i;
+  size_t i;
 
   for (i=0; i<s->irep->slen; i++) {
     if (s->irep->syms[i] == sym) return i;
@@ -684,7 +683,7 @@ scope_body(codegen_scope *s, node *tree)
   return idx - s->idx;
 }
 
-static int
+static mrb_bool
 nosplat(node *t)
 {
   while (t) {
@@ -2065,7 +2064,7 @@ codegen(codegen_scope *s, node *tree, int val)
       char *p1 = (char*)tree->car;
       char *p2 = (char*)tree->cdr;
       int ai = mrb_gc_arena_save(s->mrb);
-      int sym = new_sym(s, mrb_intern(s->mrb, REGEXP_CLASS));
+      int sym = new_sym(s, mrb_intern2(s->mrb, REGEXP_CLASS, REGEXP_CLASS_CSTR_LEN));
       int off = new_lit(s, mrb_str_new(s->mrb, p1, strlen(p1)));
       int argc = 1;
 
@@ -2092,7 +2091,7 @@ codegen(codegen_scope *s, node *tree, int val)
     if (val) {
       node *n = tree->car;
       int ai = mrb_gc_arena_save(s->mrb);
-      int sym = new_sym(s, mrb_intern(s->mrb, REGEXP_CLASS));
+      int sym = new_sym(s, mrb_intern2(s->mrb, REGEXP_CLASS, REGEXP_CLASS_CSTR_LEN));
       int argc = 1;
       int off;
       char *p;
@@ -2506,7 +2505,8 @@ codedump(mrb_state *mrb, int n)
 {
 #ifdef ENABLE_STDIO
   mrb_irep *irep = mrb->irep[n];
-  int i, ai;
+  uint32_t i;
+  int ai;
   mrb_code c;
 
   if (!irep) return;
@@ -2842,13 +2842,15 @@ codegen_start(mrb_state *mrb, parser_state *p)
   if (p->filename) {
     scope->filename = p->filename;
   }
-  if (setjmp(scope->jmp) != 0) {
+  if (setjmp(scope->jmp) == 0) {
+    // prepare irep
+    codegen(scope, p->tree, NOVAL);
+    mrb_pool_close(scope->mpool);
+    return 0;
+  }
+  else {
     return -1;
   }
-  // prepare irep
-  codegen(scope, p->tree, NOVAL);
-  mrb_pool_close(scope->mpool);
-  return 0;
 }
 
 int
diff --git a/src/crc.c b/src/crc.c
index 463c7abe6..3bda7bc26 100644
--- a/src/crc.c
+++ b/src/crc.c
@@ -6,7 +6,7 @@
 
 #include <limits.h>
 #include <stdint.h>
-#include <sys/types.h>
+#include <stddef.h>
 
 // Calculate CRC (CRC-16-CCITT)
 //
diff --git a/src/dump.c b/src/dump.c
index c2b987bc8..72ca9e0c3 100644
--- a/src/dump.c
+++ b/src/dump.c
@@ -334,8 +334,7 @@ static int
 write_lineno_record(mrb_state *mrb, mrb_irep *irep, uint8_t* bin)
 {
   uint8_t *cur = bin;
-  size_t filename_len = 0;
-  int iseq_no;
+  size_t filename_len = 0, iseq_no;
 
   cur += sizeof(uint32_t); /* record size */
 
@@ -365,13 +364,13 @@ write_lineno_record(mrb_state *mrb, mrb_irep *irep, uint8_t* bin)
 }
 
 static int
-mrb_write_section_lineno(mrb_state *mrb, int start_index, uint8_t *bin)
+mrb_write_section_lineno(mrb_state *mrb, size_t start_index, uint8_t *bin)
 {
-  int irep_no;
+  size_t irep_no;
   uint32_t section_size = 0, rlen = 0; /* size of irep record */
   uint8_t *cur = bin;
 
-  if (mrb == NULL || start_index < 0 || start_index >= mrb->irep_len || bin == NULL) {
+  if (mrb == NULL || start_index >= mrb->irep_len || bin == NULL) {
     return MRB_DUMP_INVALID_ARGUMENT;
   }
 
diff --git a/src/error.c b/src/error.c
index bd3afd2e1..df4bbc866 100644
--- a/src/error.c
+++ b/src/error.c
@@ -5,7 +5,6 @@
 */
 
 #include <errno.h>
-#include <setjmp.h>
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
@@ -147,7 +146,8 @@ exc_inspect(mrb_state *mrb, mrb_value exc)
     if (!mrb_nil_p(mesg) && RSTRING_LEN(mesg) > 0) {
       mrb_str_cat(mrb, str, ": ", 2);
       mrb_str_append(mrb, str, mesg);
-    } else {
+    }
+    else {
       mrb_str_cat(mrb, str, ": ", 2);
       mrb_str_cat_cstr(mrb, str, mrb_obj_classname(mrb, exc));
     }
@@ -218,7 +218,7 @@ mrb_exc_raise(mrb_state *mrb, mrb_value exc)
     mrb_p(mrb, exc);
     abort();
   }
-  longjmp(*(jmp_buf*)mrb->jmp, 1);
+  mrb_longjmp(mrb);
 }
 
 void
@@ -425,10 +425,12 @@ mrb_sys_fail(mrb_state *mrb, const char *mesg)
     sce = mrb_class_get(mrb, "SystemCallError");
     if (mesg != NULL) {
       mrb_funcall(mrb, mrb_obj_value(sce), "_sys_fail", 2, mrb_fixnum_value(no), mrb_str_new_cstr(mrb, mesg));
-    } else {
+    }
+    else {
       mrb_funcall(mrb, mrb_obj_value(sce), "_sys_fail", 1, mrb_fixnum_value(no));
     }
-  } else {
+  }
+  else {
     mrb_raise(mrb, E_RUNTIME_ERROR, mesg);
   }
 }
diff --git a/src/error.h b/src/error.h
index 3726cb4c4..5aa4ca374 100644
--- a/src/error.h
+++ b/src/error.h
@@ -14,5 +14,6 @@ mrb_value make_exception(mrb_state *mrb, int argc, mrb_value *argv, int isstr);
 mrb_value mrb_make_exception(mrb_state *mrb, int argc, mrb_value *argv);
 mrb_value mrb_format(mrb_state *mrb, const char *format, ...);
 void mrb_exc_print(mrb_state *mrb, struct RObject *exc);
+void mrb_longjmp(mrb_state *mrb);
 
 #endif  /* MRUBY_ERROR_H */
diff --git a/src/gc.c b/src/gc.c
index 293fbf948..8569cc085 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -11,6 +11,7 @@
 # include <limits.h>
 #endif
 #include <string.h>
+#include <stdlib.h>
 #include "mruby.h"
 #include "mruby/array.h"
 #include "mruby/class.h"
@@ -37,18 +38,23 @@
     * Gray - Marked, But the child objects are unmarked.
     * Black - Marked, the child objects are also marked.
 
-  == Two white part
+  == Two White Types
 
-  The white has a different part of A and B.
-  In sweep phase, the sweep target white is either A or B.
-  The sweep target white is switched just before sweep phase.
-  e.g. A -> B -> A -> B ...
+  There're two white color types in a flip-flop fassion: White-A and White-B,
+  which respectively represent the Current White color (the newly allocated
+  objects in the current GC cycle) and the Sweep Target White color (the
+  dead objects to be swept).
 
-  All objects are painted white when allocated.
-  This white is another the sweep target white.
-  For example, if the sweep target white is A, it's B.
-  So objects when allocated in sweep phase will be next sweep phase target.
-  Therefore, these objects will not be released accidentally in sweep phase.
+  A and B will be switched just at the beginning of the next GC cycle. At
+  that time, all the dead objects have been swept, while the newly created
+  objects in the current GC cycle which finally remains White are now
+  regarded as dead objects. Instead of traversing all the White-A objects and
+  paint them as White-B, just switch the meaning of White-A and White-B would
+  be much cheaper.
+
+  As a result, the objects we sweep in the current GC cycle are always
+  left from the previous GC cycle. This allows us to sweep objects
+  incrementally, without the disturbance of the newly created objects.
 
   == Execution Timing
 
@@ -60,7 +66,7 @@
 
   For details, see the comments for each function.
 
-  = Write Barrier
+  == Write Barrier
 
   mruby implementer, C extension library writer must write a write
   barrier when writing a pointer to an object on object's field.
@@ -69,6 +75,20 @@
     * mrb_field_write_barrier
     * mrb_write_barrier
 
+  == Generational Mode
+
+  mruby's GC offers an Generational Mode while re-using the tri-color GC
+  infrastructure. It will treat the Black objects as Old objects after each
+  sweep phase, instead of paint them to White. The key idea are still same as
+  the traditional generational GC:
+
+    * Minor GC - just traverse the Young objects (Gray objects) in the mark
+                 phase, then only sweep the newly created objects, and leave
+                 the Old objects live.
+
+    * Major GC - same as a full regular GC cycle.
+
+
   For details, see the comments for each function.
 
 */
@@ -137,39 +157,46 @@ gettimeofday_time(void)
 #endif
 
 #ifdef GC_DEBUG
-#include <assert.h>
-#define gc_assert(expect) assert(expect)
 #define DEBUG(x) (x)
 #else
-#define gc_assert(expect) ((void)0)
 #define DEBUG(x)
 #endif
 
 #define GC_STEP_SIZE 1024
 
+
 void*
-mrb_realloc(mrb_state *mrb, void *p, size_t len)
+mrb_realloc_simple(mrb_state *mrb, void *p,  size_t len)
 {
   void *p2;
 
   p2 = (mrb->allocf)(mrb, p, len, mrb->ud);
-
   if (!p2 && len > 0 && mrb->heaps) {
-    mrb_garbage_collect(mrb);
+    mrb_full_gc(mrb);
     p2 = (mrb->allocf)(mrb, p, len, mrb->ud);
   }
 
+  return p2;
+}
+
+
+void*
+mrb_realloc(mrb_state *mrb, void *p, size_t len)
+{
+  void *p2;
+
+  p2 = mrb_realloc_simple(mrb, p, len);
   if (!p2 && len) {
     if (mrb->out_of_memory) {
       /* mrb_panic(mrb); */
     }
     else {
-      mrb->out_of_memory = 1;
+      mrb->out_of_memory = TRUE;
       mrb_raise(mrb, E_RUNTIME_ERROR, "Out of memory");
     }
   }
   else {
-    mrb->out_of_memory = 0;
+    mrb->out_of_memory = FALSE;
   }
 
   return p2;
@@ -182,6 +209,12 @@ mrb_malloc(mrb_state *mrb, size_t len)
 }
 
 void*
+mrb_malloc_simple(mrb_state *mrb, size_t len)
+{
+  return mrb_realloc_simple(mrb, 0, len);
+}
+
+void*
 mrb_calloc(mrb_state *mrb, size_t nelem, size_t len)
 {
   void *p;
@@ -195,7 +228,8 @@ mrb_calloc(mrb_state *mrb, size_t nelem, size_t len)
     if (p) {
       memset(p, 0, size);
     }
-  } else {
+  }
+  else {
     p = NULL;
   }
 
@@ -295,8 +329,8 @@ add_heap(mrb_state *mrb)
 void
 mrb_init_heap(mrb_state *mrb)
 {
-  mrb->heaps = 0;
-  mrb->free_heaps = 0;
+  mrb->heaps = NULL;
+  mrb->free_heaps = NULL;
   add_heap(mrb);
   mrb->gc_interval_ratio = DEFAULT_GC_INTERVAL_RATIO;
   mrb->gc_step_ratio = DEFAULT_GC_STEP_RATIO;
@@ -353,7 +387,7 @@ mrb_obj_alloc(mrb_state *mrb, enum mrb_vtype ttype, struct RClass *cls)
   static const RVALUE RVALUE_zero = { { { MRB_TT_FALSE } } };
 
 #ifdef MRB_GC_STRESS
-  mrb_garbage_collect(mrb);
+  mrb_full_gc(mrb);
 #endif
   if (mrb->gc_threshold < mrb->live) {
     mrb_incremental_gc(mrb);
@@ -391,19 +425,29 @@ add_gray_list(mrb_state *mrb, struct RBasic *obj)
 }
 
 static void
-mark_context(mrb_state *mrb, struct mrb_context *c)
+mark_context_stack(mrb_state *mrb, struct mrb_context *c)
 {
   size_t i;
   size_t e;
-  mrb_callinfo *ci;
 
-  /* mark stack */
   e = c->stack - c->stbase;
   if (c->ci) e += c->ci->nregs;
   if (c->stbase + e > c->stend) e = c->stend - c->stbase;
   for (i=0; i<e; i++) {
     mrb_gc_mark_value(mrb, c->stbase[i]);
   }
+}
+
+static void
+mark_context(mrb_state *mrb, struct mrb_context *c)
+{
+  size_t i;
+  size_t e;
+  mrb_callinfo *ci;
+
+  /* mark stack */
+  mark_context_stack(mrb, c);
+
   /* mark ensure stack */
   e = (c->ci) ? c->ci->eidx : 0;
   for (i=0; i<e; i++) {
@@ -424,7 +468,7 @@ mark_context(mrb_state *mrb, struct mrb_context *c)
 static void
 gc_mark_children(mrb_state *mrb, struct RBasic *obj)
 {
-  gc_assert(is_gray(obj));
+  mrb_assert(is_gray(obj));
   paint_black(obj);
   mrb->gray_list = obj->gcnext;
   mrb_gc_mark(mrb, (struct RBasic*)obj->c);
@@ -521,7 +565,7 @@ mrb_gc_mark(mrb_state *mrb, struct RBasic *obj)
 {
   if (obj == 0) return;
   if (!is_white(obj)) return;
-  gc_assert((obj)->tt != MRB_TT_FREE);
+  mrb_assert((obj)->tt != MRB_TT_FREE);
   add_gray_list(mrb, obj);
 }
 
@@ -561,7 +605,7 @@ obj_free(mrb_state *mrb, struct RBasic *obj)
 
       if (e->cioff < 0) {
         mrb_free(mrb, e->stack);
-        e->stack = 0;
+        e->stack = NULL;
       }
     }
     break;
@@ -613,12 +657,11 @@ obj_free(mrb_state *mrb, struct RBasic *obj)
 static void
 root_scan_phase(mrb_state *mrb)
 {
-  int j;
-  size_t i, e;
+  size_t i, e, j;
 
   if (!is_minor_gc(mrb)) {
-    mrb->gray_list = 0;
-    mrb->variable_gray_list = 0;
+    mrb->gray_list = NULL;
+    mrb->atomic_gray_list = NULL;
   }
 
   mrb_gc_mark_gv(mrb);
@@ -728,6 +771,18 @@ gc_gray_mark(mrb_state *mrb, struct RBasic *obj)
   return children;
 }
 
+
+static void
+gc_mark_gray_list(mrb_state *mrb) {
+  while (mrb->gray_list) {
+    if (is_gray(mrb->gray_list))
+      gc_mark_children(mrb, mrb->gray_list);
+    else
+      mrb->gray_list = mrb->gray_list->gcnext;
+  }
+}
+
+
 static size_t
 incremental_marking_phase(mrb_state *mrb, size_t limit)
 {
@@ -743,22 +798,13 @@ incremental_marking_phase(mrb_state *mrb, size_t limit)
 static void
 final_marking_phase(mrb_state *mrb)
 {
-  while (mrb->gray_list) {
-    if (is_gray(mrb->gray_list))
-      gc_mark_children(mrb, mrb->gray_list);
-    else
-      mrb->gray_list = mrb->gray_list->gcnext;
-  }
-  gc_assert(mrb->gray_list == NULL);
-  mrb->gray_list = mrb->variable_gray_list;
-  mrb->variable_gray_list = 0;
-  while (mrb->gray_list) {
-    if (is_gray(mrb->gray_list))
-      gc_mark_children(mrb, mrb->gray_list);
-    else
-      mrb->gray_list = mrb->gray_list->gcnext;
-  }
-  gc_assert(mrb->gray_list == NULL);
+  mark_context_stack(mrb, mrb->root_c);
+  gc_mark_gray_list(mrb);
+  mrb_assert(mrb->gray_list == NULL);
+  mrb->gray_list = mrb->atomic_gray_list;
+  mrb->atomic_gray_list = NULL;
+  gc_mark_gray_list(mrb);
+  mrb_assert(mrb->gray_list == NULL);
 }
 
 static void
@@ -858,17 +904,31 @@ incremental_gc(mrb_state *mrb, size_t limit)
   }
   default:
     /* unknown state */
-    gc_assert(0);
+    mrb_assert(0);
     return 0;
   }
 }
 
 static void
-advance_phase(mrb_state *mrb, enum gc_state to_state)
+incremental_gc_until(mrb_state *mrb, enum gc_state to_state)
 {
-  while (mrb->gc_state != to_state) {
+  do {
     incremental_gc(mrb, ~0);
+  } while (mrb->gc_state != to_state);
+}
+
+static void
+incremental_gc_step(mrb_state *mrb)
+{
+  size_t limit = 0, result = 0;
+  limit = (GC_STEP_SIZE/100) * mrb->gc_step_ratio;
+  while (result < limit) {
+    result += incremental_gc(mrb, limit);
+    if (mrb->gc_state == GC_STATE_NONE)
+      break;
   }
+
+  mrb->gc_threshold = mrb->live + GC_STEP_SIZE;
 }
 
 static void
@@ -876,15 +936,15 @@ clear_all_old(mrb_state *mrb)
 {
   size_t origin_mode = mrb->is_generational_gc_mode;
 
-  gc_assert(is_generational(mrb));
+  mrb_assert(is_generational(mrb));
   if (is_major_gc(mrb)) {
-    advance_phase(mrb, GC_STATE_NONE);
+    incremental_gc_until(mrb, GC_STATE_NONE);
   }
 
   mrb->is_generational_gc_mode = FALSE;
   prepare_incremental_sweep(mrb);
-  advance_phase(mrb, GC_STATE_NONE);
-  mrb->variable_gray_list = mrb->gray_list = NULL;
+  incremental_gc_until(mrb, GC_STATE_NONE);
+  mrb->atomic_gray_list = mrb->gray_list = NULL;
   mrb->is_generational_gc_mode = origin_mode;
 }
 
@@ -897,26 +957,19 @@ mrb_incremental_gc(mrb_state *mrb)
   GC_TIME_START;
 
   if (is_minor_gc(mrb)) {
-    do {
-      incremental_gc(mrb, ~0);
-    } while (mrb->gc_state != GC_STATE_NONE);
+    incremental_gc_until(mrb, GC_STATE_NONE);
   }
   else {
-    size_t limit = 0, result = 0;
-    limit = (GC_STEP_SIZE/100) * mrb->gc_step_ratio;
-    while (result < limit) {
-      result += incremental_gc(mrb, limit);
-      if (mrb->gc_state == GC_STATE_NONE)
-        break;
-    }
+    incremental_gc_step(mrb);
   }
 
   if (mrb->gc_state == GC_STATE_NONE) {
-    gc_assert(mrb->live >= mrb->gc_live_after_mark);
+    mrb_assert(mrb->live >= mrb->gc_live_after_mark);
     mrb->gc_threshold = (mrb->gc_live_after_mark/100) * mrb->gc_interval_ratio;
     if (mrb->gc_threshold < GC_STEP_SIZE) {
       mrb->gc_threshold = GC_STEP_SIZE;
     }
+
     if (is_major_gc(mrb)) {
       mrb->majorgc_old_threshold = mrb->gc_live_after_mark/100 * DEFAULT_MAJOR_GC_INC_RATIO;
       mrb->gc_full = FALSE;
@@ -928,28 +981,21 @@ mrb_incremental_gc(mrb_state *mrb)
       }
     }
   }
-  else {
-    mrb->gc_threshold = mrb->live + GC_STEP_SIZE;
-  }
-
 
   GC_TIME_STOP_AND_REPORT;
 }
 
+/* Perform a full gc cycle */
 void
-mrb_garbage_collect(mrb_state *mrb)
+mrb_full_gc(mrb_state *mrb)
 {
-  size_t max_limit = ~0;
-
   if (mrb->gc_disabled) return;
-  GC_INVOKE_TIME_REPORT("mrb_garbage_collect()");
+  GC_INVOKE_TIME_REPORT("mrb_full_gc()");
   GC_TIME_START;
 
   if (mrb->gc_state == GC_STATE_SWEEP) {
     /* finish sweep phase */
-    while (mrb->gc_state != GC_STATE_NONE) {
-      incremental_gc(mrb, max_limit);
-    }
+    incremental_gc_until(mrb, GC_STATE_NONE);
   }
 
   /* clean all black object as old */
@@ -958,10 +1004,7 @@ mrb_garbage_collect(mrb_state *mrb)
     mrb->gc_full = TRUE;
   }
 
-  do {
-    incremental_gc(mrb, max_limit);
-  } while (mrb->gc_state != GC_STATE_NONE);
-
+  incremental_gc_until(mrb, GC_STATE_NONE);
   mrb->gc_threshold = (mrb->gc_live_after_mark/100) * mrb->gc_interval_ratio;
 
   if (is_generational(mrb)) {
@@ -972,6 +1015,12 @@ mrb_garbage_collect(mrb_state *mrb)
   GC_TIME_STOP_AND_REPORT;
 }
 
+void
+mrb_garbage_collect(mrb_state *mrb)
+{
+  mrb_full_gc(mrb);
+}
+
 int
 mrb_gc_arena_save(mrb_state *mrb)
 {
@@ -995,14 +1044,14 @@ mrb_field_write_barrier(mrb_state *mrb, struct RBasic *obj, struct RBasic *value
   if (!is_black(obj)) return;
   if (!is_white(value)) return;
 
-  gc_assert(!is_dead(mrb, value) && !is_dead(mrb, obj));
-  gc_assert(is_generational(mrb) || mrb->gc_state != GC_STATE_NONE);
+  mrb_assert(!is_dead(mrb, value) && !is_dead(mrb, obj));
+  mrb_assert(is_generational(mrb) || mrb->gc_state != GC_STATE_NONE);
 
   if (is_generational(mrb) || mrb->gc_state == GC_STATE_MARK) {
     add_gray_list(mrb, value);
   }
   else {
-    gc_assert(mrb->gc_state == GC_STATE_SWEEP);
+    mrb_assert(mrb->gc_state == GC_STATE_SWEEP);
     paint_partial_white(mrb, obj); /* for never write barriers */
   }
 }
@@ -1021,11 +1070,11 @@ mrb_write_barrier(mrb_state *mrb, struct RBasic *obj)
 {
   if (!is_black(obj)) return;
 
-  gc_assert(!is_dead(mrb, obj));
-  gc_assert(is_generational(mrb) || mrb->gc_state != GC_STATE_NONE);
+  mrb_assert(!is_dead(mrb, obj));
+  mrb_assert(is_generational(mrb) || mrb->gc_state != GC_STATE_NONE);
   paint_gray(obj);
-  obj->gcnext = mrb->variable_gray_list;
-  mrb->variable_gray_list = obj;
+  obj->gcnext = mrb->atomic_gray_list;
+  mrb->atomic_gray_list = obj;
 }
 
 /*
@@ -1039,7 +1088,7 @@ mrb_write_barrier(mrb_state *mrb, struct RBasic *obj)
 static mrb_value
 gc_start(mrb_state *mrb, mrb_value obj)
 {
-  mrb_garbage_collect(mrb);
+  mrb_full_gc(mrb);
   return mrb_nil_value();
 }
 
@@ -1159,11 +1208,11 @@ change_gen_gc_mode(mrb_state *mrb, mrb_int enable)
 {
   if (is_generational(mrb) && !enable) {
     clear_all_old(mrb);
-    gc_assert(mrb->gc_state == GC_STATE_NONE);
+    mrb_assert(mrb->gc_state == GC_STATE_NONE);
     mrb->gc_full = FALSE;
   }
   else if (!is_generational(mrb) && enable) {
-    advance_phase(mrb, GC_STATE_NONE);
+    incremental_gc_until(mrb, GC_STATE_NONE);
     mrb->majorgc_old_threshold = mrb->gc_live_after_mark/100 * DEFAULT_MAJOR_GC_INC_RATIO;
     mrb->gc_full = FALSE;
   }
@@ -1271,7 +1320,7 @@ test_mrb_field_write_barrier(void)
   mrb->gc_state = GC_STATE_MARK;
   mrb_field_write_barrier(mrb, obj, value);
 
-  gc_assert(is_gray(value));
+  mrb_assert(is_gray(value));
 
 
   puts("  in GC_STATE_SWEEP");
@@ -1279,8 +1328,8 @@ test_mrb_field_write_barrier(void)
   mrb->gc_state = GC_STATE_SWEEP;
   mrb_field_write_barrier(mrb, obj, value);
 
-  gc_assert(obj->color & mrb->current_white_part);
-  gc_assert(value->color & mrb->current_white_part);
+  mrb_assert(obj->color & mrb->current_white_part);
+  mrb_assert(value->color & mrb->current_white_part);
 
 
   puts("  fail with black");
@@ -1289,7 +1338,7 @@ test_mrb_field_write_barrier(void)
   paint_partial_white(mrb,value);
   mrb_field_write_barrier(mrb, obj, value);
 
-  gc_assert(obj->color & mrb->current_white_part);
+  mrb_assert(obj->color & mrb->current_white_part);
 
 
   puts("  fail with gray");
@@ -1298,7 +1347,7 @@ test_mrb_field_write_barrier(void)
   paint_gray(value);
   mrb_field_write_barrier(mrb, obj, value);
 
-  gc_assert(is_gray(value));
+  mrb_assert(is_gray(value));
 
 
   {
@@ -1311,7 +1360,7 @@ test_mrb_field_write_barrier(void)
     mrb->gc_state = GC_STATE_MARK;
     mrb_field_write_barrier_value(mrb, obj, value);
 
-    gc_assert(is_gray(mrb_basic_ptr(value)));
+    mrb_assert(is_gray(mrb_basic_ptr(value)));
   }
 
   mrb_close(mrb);
@@ -1331,15 +1380,15 @@ test_mrb_write_barrier(void)
   mrb->gc_state = GC_STATE_MARK;
   mrb_write_barrier(mrb, obj);
 
-  gc_assert(is_gray(obj));
-  gc_assert(mrb->variable_gray_list == obj);
+  mrb_assert(is_gray(obj));
+  mrb_assert(mrb->atomic_gray_list == obj);
 
 
   puts("  fail with gray");
   paint_gray(obj);
   mrb_write_barrier(mrb, obj);
 
-  gc_assert(is_gray(obj));
+  mrb_assert(is_gray(obj));
 
   mrb_close(mrb);
 }
@@ -1352,17 +1401,17 @@ test_add_gray_list(void)
 
   puts("test_add_gray_list");
   change_gen_gc_mode(mrb, FALSE);
-  gc_assert(mrb->gray_list == NULL);
+  mrb_assert(mrb->gray_list == NULL);
   obj1 = mrb_basic_ptr(mrb_str_new_cstr(mrb, "test"));
   add_gray_list(mrb, obj1);
-  gc_assert(mrb->gray_list == obj1);
-  gc_assert(is_gray(obj1));
+  mrb_assert(mrb->gray_list == obj1);
+  mrb_assert(is_gray(obj1));
 
   obj2 = mrb_basic_ptr(mrb_str_new_cstr(mrb, "test"));
   add_gray_list(mrb, obj2);
-  gc_assert(mrb->gray_list == obj2);
-  gc_assert(mrb->gray_list->gcnext == obj1);
-  gc_assert(is_gray(obj2));
+  mrb_assert(mrb->gray_list == obj2);
+  mrb_assert(mrb->gray_list->gcnext == obj1);
+  mrb_assert(is_gray(obj2));
 
   mrb_close(mrb);
 }
@@ -1381,8 +1430,8 @@ test_gc_gray_mark(void)
   obj = (struct RBasic*)mrb->object_class;
   paint_gray(obj);
   gray_num = gc_gray_mark(mrb, obj);
-  gc_assert(is_black(obj));
-  gc_assert(gray_num > 1);
+  mrb_assert(is_black(obj));
+  mrb_assert(gray_num > 1);
 
   puts("  in MRB_TT_ARRAY");
   obj_v = mrb_ary_new(mrb);
@@ -1391,9 +1440,9 @@ test_gc_gray_mark(void)
   paint_partial_white(mrb, mrb_basic_ptr(value_v));
   mrb_ary_push(mrb, obj_v, value_v);
   gray_num = gc_gray_mark(mrb, mrb_basic_ptr(obj_v));
-  gc_assert(is_black(mrb_basic_ptr(obj_v)));
-  gc_assert(is_gray(mrb_basic_ptr(value_v)));
-  gc_assert(gray_num == 1);
+  mrb_assert(is_black(mrb_basic_ptr(obj_v)));
+  mrb_assert(is_gray(mrb_basic_ptr(value_v)));
+  mrb_assert(gray_num == 1);
 
   mrb_close(mrb);
 }
@@ -1409,16 +1458,16 @@ test_incremental_gc(void)
   puts("test_incremental_gc");
   change_gen_gc_mode(mrb, FALSE);
 
-  puts("  in mrb_garbage_collect");
-  mrb_garbage_collect(mrb);
+  puts("  in mrb_full_gc");
+  mrb_full_gc(mrb);
 
-  gc_assert(mrb->gc_state == GC_STATE_NONE);
+  mrb_assert(mrb->gc_state == GC_STATE_NONE);
   puts("  in GC_STATE_NONE");
   incremental_gc(mrb, max);
-  gc_assert(mrb->gc_state == GC_STATE_MARK);
+  mrb_assert(mrb->gc_state == GC_STATE_MARK);
   puts("  in GC_STATE_MARK");
-  advance_phase(mrb, GC_STATE_SWEEP);
-  gc_assert(mrb->gc_state == GC_STATE_SWEEP);
+  incremental_gc_until(mrb, GC_STATE_SWEEP);
+  mrb_assert(mrb->gc_state == GC_STATE_SWEEP);
 
   puts("  in GC_STATE_SWEEP");
   page = mrb->heaps;
@@ -1438,13 +1487,13 @@ test_incremental_gc(void)
     total += MRB_HEAP_PAGE_SIZE;
   }
 
-  gc_assert(mrb->gray_list == NULL);
+  mrb_assert(mrb->gray_list == NULL);
 
   incremental_gc(mrb, max);
-  gc_assert(mrb->gc_state == GC_STATE_SWEEP);
+  mrb_assert(mrb->gc_state == GC_STATE_SWEEP);
 
   incremental_gc(mrb, max);
-  gc_assert(mrb->gc_state == GC_STATE_NONE);
+  mrb_assert(mrb->gc_state == GC_STATE_NONE);
 
   free = (RVALUE*)mrb->heaps->freelist;
   while (free) {
@@ -1452,30 +1501,30 @@ test_incremental_gc(void)
    free = (RVALUE*)free->as.free.next;
   }
 
-  gc_assert(mrb->live == live);
-  gc_assert(mrb->live == total-freed);
+  mrb_assert(mrb->live == live);
+  mrb_assert(mrb->live == total-freed);
 
   puts("test_incremental_gc(gen)");
-  advance_phase(mrb, GC_STATE_SWEEP);
+  incremental_gc_until(mrb, GC_STATE_SWEEP);
   change_gen_gc_mode(mrb, TRUE);
 
-  gc_assert(mrb->gc_full == FALSE);
-  gc_assert(mrb->gc_state == GC_STATE_NONE);
+  mrb_assert(mrb->gc_full == FALSE);
+  mrb_assert(mrb->gc_state == GC_STATE_NONE);
 
   puts("  in minor");
-  gc_assert(is_minor_gc(mrb));
-  gc_assert(mrb->majorgc_old_threshold > 0);
+  mrb_assert(is_minor_gc(mrb));
+  mrb_assert(mrb->majorgc_old_threshold > 0);
   mrb->majorgc_old_threshold = 0;
   mrb_incremental_gc(mrb);
-  gc_assert(mrb->gc_full == TRUE);
-  gc_assert(mrb->gc_state == GC_STATE_NONE);
+  mrb_assert(mrb->gc_full == TRUE);
+  mrb_assert(mrb->gc_state == GC_STATE_NONE);
 
   puts("  in major");
-  gc_assert(is_major_gc(mrb));
+  mrb_assert(is_major_gc(mrb));
   do {
     mrb_incremental_gc(mrb);
   } while (mrb->gc_state != GC_STATE_NONE);
-  gc_assert(mrb->gc_full == FALSE);
+  mrb_assert(mrb->gc_full == FALSE);
 
   mrb_close(mrb);
 }
@@ -1490,12 +1539,12 @@ test_incremental_sweep_phase(void)
   add_heap(mrb);
   mrb->sweeps = mrb->heaps;
 
-  gc_assert(mrb->heaps->next->next == NULL);
-  gc_assert(mrb->free_heaps->next->next == NULL);
+  mrb_assert(mrb->heaps->next->next == NULL);
+  mrb_assert(mrb->free_heaps->next->next == NULL);
   incremental_sweep_phase(mrb, MRB_HEAP_PAGE_SIZE*3);
 
-  gc_assert(mrb->heaps->next == NULL);
-  gc_assert(mrb->heaps == mrb->free_heaps);
+  mrb_assert(mrb->heaps->next == NULL);
+  mrb_assert(mrb->heaps == mrb->free_heaps);
 
   mrb_close(mrb);
 }
diff --git a/src/hash.c b/src/hash.c
index e31f7b3d7..1ffaed5fb 100644
--- a/src/hash.c
+++ b/src/hash.c
@@ -145,7 +145,9 @@ mrb_hash_set(mrb_state *mrb, mrb_value hash, mrb_value key, mrb_value val) /* mr
   k = kh_get(ht, h, key);
   if (k == kh_end(h)) {
     /* expand */
+    int ai = mrb_gc_arena_save(mrb);
     k = kh_put(ht, h, KEY(key));
+    mrb_gc_arena_restore(mrb, ai);
   }
 
   kh_value(h, k) = val;
@@ -169,7 +171,9 @@ mrb_hash_dup(mrb_state *mrb, mrb_value hash)
 
     for (k = kh_begin(h); k != kh_end(h); k++) {
       if (kh_exist(h,k)) {
+        int ai = mrb_gc_arena_save(mrb);
         ret_k = kh_put(ht, ret_h, KEY(kh_key(h,k)));
+        mrb_gc_arena_restore(mrb, ai);
         kh_val(ret_h, ret_k) = kh_val(h,k);
       }
     }
@@ -772,16 +776,9 @@ mrb_value
 mrb_hash_empty_p(mrb_state *mrb, mrb_value self)
 {
   khash_t(ht) *h = RHASH_TBL(self);
-  mrb_bool empty_p;
 
-  if (h) {
-    empty_p = (kh_size(h) == 0);
-  }
-  else {
-    empty_p = 1;
-  }
-
-  return mrb_bool_value(empty_p);
+  if (h) return mrb_bool_value(kh_size(h) == 0);
+  return mrb_true_value();
 }
 
 static mrb_value
@@ -921,17 +918,12 @@ mrb_hash_has_keyWithKey(mrb_state *mrb, mrb_value hash, mrb_value key)
 {
   khash_t(ht) *h = RHASH_TBL(hash);
   khiter_t k;
-  mrb_bool result;
 
   if (h) {
     k = kh_get(ht, h, key);
-    result = (k != kh_end(h));
-  }
-  else {
-    result = 0;
+    return mrb_bool_value(k != kh_end(h));
   }
-
-  return mrb_bool_value(result);
+  return mrb_false_value();
 }
 
 /* 15.2.13.4.13 */
diff --git a/src/kernel.c b/src/kernel.c
index 4b3bed0d8..4b426c6b4 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -26,7 +26,7 @@ typedef enum {
     NOEX_RESPONDS  = 0x80
 } mrb_method_flag_t;
 
-int
+mrb_bool
 mrb_obj_basic_to_s_p(mrb_state *mrb, mrb_value obj)
 {
     struct RProc *me = mrb_method_search(mrb, mrb_class(mrb, obj), mrb_intern2(mrb, "to_s", 4));
@@ -521,7 +521,7 @@ mrb_obj_instance_eval(mrb_state *mrb, mrb_value self)
   return mrb_yield_internal(mrb, b, 0, 0, self, c);
 }
 
-int
+mrb_bool
 mrb_obj_is_instance_of(mrb_state *mrb, mrb_value obj, struct RClass* c)
 {
   if (mrb_obj_class(mrb, obj) == c) return TRUE;
@@ -549,15 +549,40 @@ obj_is_instance_of(mrb_state *mrb, mrb_value self)
 }
 
 static void
-check_iv_name(mrb_state *mrb, mrb_sym id)
+valid_iv_name(mrb_state *mrb, mrb_sym iv_name_id, const char* s, size_t len)
+{
+  if (len < 2 || !(s[0] == '@' && s[1] != '@')) {
+    mrb_name_error(mrb, iv_name_id, "`%S' is not allowed as an instance variable name", mrb_sym2str(mrb, iv_name_id));
+  }
+}
+
+static void
+check_iv_name(mrb_state *mrb, mrb_sym iv_name_id)
 {
   const char *s;
   size_t len;
 
-  s = mrb_sym2name_len(mrb, id, &len);
-  if (len < 2 || !(s[0] == '@' && s[1] != '@')) {
-    mrb_name_error(mrb, id, "`%S' is not allowed as an instance variable name", mrb_sym2str(mrb, id));
+  s = mrb_sym2name_len(mrb, iv_name_id, &len);
+  valid_iv_name(mrb, iv_name_id, s, len);
+}
+
+static mrb_sym
+get_valid_iv_sym(mrb_state *mrb, mrb_value iv_name)
+{
+  mrb_sym iv_name_id;
+
+  mrb_assert(mrb_symbol_p(iv_name) || mrb_string_p(iv_name));
+
+  if (mrb_string_p(iv_name)) {
+    iv_name_id = mrb_intern_cstr(mrb, RSTRING_PTR(iv_name));
+    valid_iv_name(mrb, iv_name_id, RSTRING_PTR(iv_name), RSTRING_LEN(iv_name));
+  }
+  else {
+    iv_name_id = mrb_symbol(iv_name);
+    check_iv_name(mrb, iv_name_id);
   }
+
+  return iv_name_id;
 }
 
 /* 15.3.1.3.20 */
@@ -582,10 +607,11 @@ mrb_value
 mrb_obj_ivar_defined(mrb_state *mrb, mrb_value self)
 {
   mrb_sym mid;
+  mrb_value sym;
   mrb_bool defined_p;
 
-  mrb_get_args(mrb, "n", &mid);
-  check_iv_name(mrb, mid);
+  mrb_get_args(mrb, "o", &sym);
+  mid = get_valid_iv_sym(mrb, sym);
   defined_p = mrb_obj_iv_defined(mrb, mrb_obj_ptr(self), mid);
 
   return mrb_bool_value(defined_p);
@@ -614,12 +640,13 @@ mrb_obj_ivar_defined(mrb_state *mrb, mrb_value self)
 mrb_value
 mrb_obj_ivar_get(mrb_state *mrb, mrb_value self)
 {
-  mrb_sym id;
+  mrb_sym iv_name_id;
+  mrb_value iv_name;
 
-  mrb_get_args(mrb, "n", &id);
+  mrb_get_args(mrb, "o", &iv_name);
 
-  check_iv_name(mrb, id);
-  return mrb_iv_get(mrb, self, id);
+  iv_name_id = get_valid_iv_sym(mrb, iv_name);
+  return mrb_iv_get(mrb, self, iv_name_id);
 }
 
 /* 15.3.1.3.22 */
@@ -645,12 +672,13 @@ mrb_obj_ivar_get(mrb_state *mrb, mrb_value self)
 mrb_value
 mrb_obj_ivar_set(mrb_state *mrb, mrb_value self)
 {
-  mrb_sym id;
-  mrb_value val;
+  mrb_sym iv_name_id;
+  mrb_value iv_name, val;
+
+  mrb_get_args(mrb, "oo", &iv_name, &val);
 
-  mrb_get_args(mrb, "no", &id, &val);
-  check_iv_name(mrb, id);
-  mrb_iv_set(mrb, self, id, val);
+  iv_name_id = get_valid_iv_sym(mrb, iv_name);
+  mrb_iv_set(mrb, self, iv_name_id, val);
   return val;
 }
 
@@ -938,7 +966,7 @@ mrb_obj_remove_instance_variable(mrb_state *mrb, mrb_value self)
   return val;
 }
 
-static inline int
+static inline mrb_bool
 basic_obj_respond_to(mrb_state *mrb, mrb_value obj, mrb_sym id, int pub)
 {
   return mrb_respond_to(mrb, obj, id);
@@ -1101,5 +1129,5 @@ mrb_init_kernel(mrb_state *mrb)
   mrb_define_method(mrb, krn, "to_s",                       mrb_any_to_s,                    MRB_ARGS_NONE());    /* 15.3.1.3.46 */
 
   mrb_include_module(mrb, mrb->object_class, mrb->kernel_module);
-  mrb_alias_method(mrb, mrb->module_class, mrb_intern(mrb, "dup"), mrb_intern(mrb, "clone"));
+  mrb_alias_method(mrb, mrb->module_class, mrb_intern2(mrb, "dup", 3), mrb_intern2(mrb, "clone", 5));
 }
diff --git a/src/load.c b/src/load.c
index 62010e425..092ddbde8 100644
--- a/src/load.c
+++ b/src/load.c
@@ -187,7 +187,6 @@ read_rite_section_irep(mrb_state *mrb, const uint8_t *bin)
 {
   int result;
   size_t sirep;
-  size_t i;
   uint32_t len;
   uint16_t nirep;
   uint16_t n;
@@ -200,14 +199,14 @@ read_rite_section_irep(mrb_state *mrb, const uint8_t *bin)
   nirep = bin_to_uint16(header->nirep);
 
   //Read Binary Data Section
-  for (n = 0, i = sirep; n < nirep; n++, i++) {
+  for (n = 0; n < nirep; n++) {
     result = read_rite_irep_record(mrb, bin, &len);
     if (result != MRB_DUMP_OK)
       goto error_exit;
     bin += len;
   }
 
-  result = sirep + bin_to_uint16(header->sirep);
+  result = nirep;
 error_exit:
   if (result < MRB_DUMP_OK) {
     irep_free(sirep, mrb);
@@ -368,7 +367,7 @@ mrb_read_irep(mrb_state *mrb, const uint8_t *bin)
     bin += bin_to_uint32(section_header->section_size);
   } while (memcmp(section_header->section_identify, RITE_BINARY_EOF, sizeof(section_header->section_identify)) != 0);
 
-  return total_nirep;
+  return sirep;
 }
 
 static void
@@ -464,7 +463,6 @@ read_rite_section_irep_file(mrb_state *mrb, FILE *fp)
 {
   int32_t result;
   size_t sirep;
-  size_t i;
   uint16_t nirep;
   uint16_t n;
   uint32_t len, buf_size;
@@ -488,7 +486,7 @@ read_rite_section_irep_file(mrb_state *mrb, FILE *fp)
   }
 
   //Read Binary Data Section
-  for (n = 0, i = sirep; n < nirep; n++, i++) {
+  for (n = 0; n < nirep; n++) {
     void *ptr;
 
     if (fread(buf, record_header_size, 1, fp) == 0) {
@@ -516,7 +514,7 @@ read_rite_section_irep_file(mrb_state *mrb, FILE *fp)
       goto error_exit;
   }
 
-  result = sirep + bin_to_uint16(header.sirep);
+  result = nirep;
 error_exit:
   if (buf) {
     mrb_free(mrb, buf);
@@ -539,7 +537,9 @@ mrb_read_irep_file(mrb_state *mrb, FILE* fp)
   size_t sirep;
   struct rite_section_header section_header;
   long fpos;
-  const size_t block_size = 1 << 14;
+  size_t block_size = 1 << 14;
+  const uint8_t block_fallback_count = 4;
+  int i;
   const size_t buf_size = sizeof(struct rite_binary_header);
 
   if ((mrb == NULL) || (fp == NULL)) {
@@ -564,7 +564,10 @@ mrb_read_irep_file(mrb_state *mrb, FILE* fp)
   /* verify CRC */
   fpos = ftell(fp);
   /* You don't need use SIZE_ERROR as block_size is enough small. */
-  buf = mrb_malloc(mrb, block_size);
+  for (i = 0; i < block_fallback_count; i++,block_size >>= 1){
+    buf = mrb_malloc_simple(mrb, block_size);
+    if (buf) break;  
+  }
   if (!buf) {
     return MRB_DUMP_GENERAL_FAILURE;
   }
@@ -609,7 +612,7 @@ mrb_read_irep_file(mrb_state *mrb, FILE* fp)
     fseek(fp, fpos + section_size, SEEK_SET);
   } while (memcmp(section_header.section_identify, RITE_BINARY_EOF, sizeof(section_header.section_identify)) != 0);
 
-  return total_nirep;
+  return sirep;
 }
 
 mrb_value
diff --git a/src/numeric.c b/src/numeric.c
index 91843fdf8..cfde61c8c 100644
--- a/src/numeric.c
+++ b/src/numeric.c
@@ -4,7 +4,6 @@
 ** See Copyright Notice in mruby.h
 */
 
-#include <assert.h>
 #include <float.h>
 #if defined(__FreeBSD__) && __FreeBSD__ < 4
 # include <floatingpoint.h>
@@ -240,7 +239,8 @@ mrb_flo_to_str(mrb_state *mrb, mrb_value flo, int max_digit)
       *(c++) = 'e';
       if (exp > 0) {
         *(c++) = '+';
-      } else {
+      }
+      else {
         *(c++) = '-';
         exp = -exp;
       }
@@ -781,7 +781,7 @@ fixdivmod(mrb_state *mrb, mrb_int x, mrb_int y, mrb_int *divp, mrb_int *modp)
 {
   mrb_int div, mod;
 
-  /* TODO: add assert(y != 0) to make sure */
+  /* TODO: add mrb_assert(y != 0) to make sure */
 
   if (y < 0) {
     if (x < 0)
@@ -998,7 +998,7 @@ fix_xor(mrb_state *mrb, mrb_value x)
 #define NUMERIC_SHIFT_WIDTH_MAX (sizeof(mrb_int)*CHAR_BIT-1)
 
 static mrb_value
-lshift(mrb_state *mrb, mrb_int val, int width)
+lshift(mrb_state *mrb, mrb_int val, size_t width)
 {
   if (width > NUMERIC_SHIFT_WIDTH_MAX) {
     mrb_raisef(mrb, E_RANGE_ERROR, "width(%S) > (%S:sizeof(mrb_int)*CHAR_BIT-1)",
@@ -1010,7 +1010,7 @@ lshift(mrb_state *mrb, mrb_int val, int width)
 }
 
 static mrb_value
-rshift(mrb_int val, int width)
+rshift(mrb_int val, size_t width)
 {
   if (width >= NUMERIC_SHIFT_WIDTH_MAX) {
     if (val < 0) {
@@ -1253,12 +1253,14 @@ mrb_fixnum_to_str(mrb_state *mrb, mrb_value x, int base)
 
   if (val == 0) {
     *--b = '0';
-  } else if (val < 0) {
+  }
+  else if (val < 0) {
     do {
       *--b = mrb_digitmap[-(val % base)];
     } while (val /= base);
     *--b = '-';
-  } else {
+  }
+  else {
     do {
       *--b = mrb_digitmap[(int)(val % base)];
     } while (val /= base);
diff --git a/src/object.c b/src/object.c
index a2162f77f..5b2278767 100644
--- a/src/object.c
+++ b/src/object.c
@@ -5,18 +5,19 @@
 */
 
 #include "mruby.h"
+#include "mruby/array.h"
 #include "mruby/class.h"
 #include "mruby/numeric.h"
 #include "mruby/string.h"
 #include "error.h"
 
-int
+mrb_bool
 mrb_obj_eq(mrb_state *mrb, mrb_value v1, mrb_value v2)
 {
   if (mrb_type(v1) != mrb_type(v2)) return FALSE;
   switch (mrb_type(v1)) {
   case MRB_TT_TRUE:
-    return 1;
+    return TRUE;
 
   case MRB_TT_FALSE:
   case MRB_TT_FIXNUM:
@@ -32,14 +33,14 @@ mrb_obj_eq(mrb_state *mrb, mrb_value v1, mrb_value v2)
   }
 }
 
-int
+mrb_bool
 mrb_obj_equal(mrb_state *mrb, mrb_value v1, mrb_value v2)
 {
   /* temporary definition */
   return mrb_obj_eq(mrb, v1, v2);
 }
 
-int
+mrb_bool
 mrb_equal(mrb_state *mrb, mrb_value obj1, mrb_value obj2)
 {
   mrb_value result;
@@ -67,7 +68,7 @@ mrb_equal(mrb_state *mrb, mrb_value obj1, mrb_value obj2)
 static mrb_value
 mrb_true(mrb_state *mrb, mrb_value obj)
 {
-    return mrb_true_value();
+  return mrb_true_value();
 }
 
 /* 15.2.4.3.5  */
@@ -171,9 +172,6 @@ true_to_s(mrb_state *mrb, mrb_value obj)
 static mrb_value
 true_or(mrb_state *mrb, mrb_value obj)
 {
-  mrb_bool obj2;
-
-  mrb_get_args(mrb, "b", &obj2);
   return mrb_true_value();
 }
 
@@ -202,9 +200,6 @@ true_or(mrb_state *mrb, mrb_value obj)
 static mrb_value
 false_and(mrb_state *mrb, mrb_value obj)
 {
-  mrb_bool obj2;
-
-  mrb_get_args(mrb, "b", &obj2);
   return mrb_false_value();
 }
 
@@ -302,7 +297,7 @@ convert_type(mrb_state *mrb, mrb_value val, const char *tname, const char *metho
 {
   mrb_sym m = 0;
 
-  m = mrb_intern(mrb, method);
+  m = mrb_intern_cstr(mrb, method);
   if (!mrb_respond_to(mrb, val, m)) {
     if (raise) {
       mrb_raisef(mrb, E_TYPE_ERROR, "can't convert %S into %S", val, mrb_str_new_cstr(mrb, tname));
@@ -318,18 +313,18 @@ convert_type(mrb_state *mrb, mrb_value val, const char *tname, const char *metho
 mrb_value
 mrb_check_to_integer(mrb_state *mrb, mrb_value val, const char *method)
 {
-    mrb_value v;
+  mrb_value v;
 
-    if (mrb_type(val) == MRB_TT_FIXNUM) return val;
-    v = convert_type(mrb, val, "Integer", method, FALSE);
-    if (mrb_nil_p(v) || mrb_type(v) != MRB_TT_FIXNUM) {
-      return mrb_nil_value();
-    }
-    return v;
+  if (mrb_type(val) == MRB_TT_FIXNUM) return val;
+  v = convert_type(mrb, val, "Integer", method, FALSE);
+  if (mrb_nil_p(v) || mrb_type(v) != MRB_TT_FIXNUM) {
+    return mrb_nil_value();
+  }
+  return v;
 }
 
 mrb_value
-mrb_convert_type(mrb_state *mrb, mrb_value val, mrb_int type, const char *tname, const char *method)
+mrb_convert_type(mrb_state *mrb, mrb_value val, enum mrb_vtype type, const char *tname, const char *method)
 {
   mrb_value v;
 
@@ -343,7 +338,7 @@ mrb_convert_type(mrb_state *mrb, mrb_value val, mrb_int type, const char *tname,
 }
 
 mrb_value
-mrb_check_convert_type(mrb_state *mrb, mrb_value val, mrb_int type, const char *tname, const char *method)
+mrb_check_convert_type(mrb_state *mrb, mrb_value val, enum mrb_vtype type, const char *tname, const char *method)
 {
   mrb_value v;
 
@@ -354,8 +349,8 @@ mrb_check_convert_type(mrb_state *mrb, mrb_value val, mrb_int type, const char *
 }
 
 static const struct types {
-    unsigned char type;
-    const char *name;
+  unsigned char type;
+  const char *name;
 } builtin_types[] = {
 //    {MRB_TT_NIL,  "nil"},
   {MRB_TT_FALSE,  "false"},
@@ -473,7 +468,7 @@ mrb_any_to_s(mrb_state *mrb, mrb_value obj)
  *     b.kind_of? M       #=> true
  */
 
-int
+mrb_bool
 mrb_obj_is_kind_of(mrb_state *mrb, mrb_value obj, struct RClass *c)
 {
   struct RClass *cl = mrb_class(mrb, obj);
@@ -499,21 +494,21 @@ mrb_obj_is_kind_of(mrb_state *mrb, mrb_value obj, struct RClass *c)
 static mrb_value
 mrb_to_integer(mrb_state *mrb, mrb_value val, const char *method)
 {
-    mrb_value v;
+  mrb_value v;
 
-    if (mrb_fixnum_p(val)) return val;
-    v = convert_type(mrb, val, "Integer", method, TRUE);
-    if (!mrb_obj_is_kind_of(mrb, v, mrb->fixnum_class)) {
-      mrb_raisef(mrb, E_TYPE_ERROR, "can't convert %S to Integer (%S#%S gives %S)",
-                 val, val, mrb_str_new_cstr(mrb, method), v);
-    }
-    return v;
+  if (mrb_fixnum_p(val)) return val;
+  v = convert_type(mrb, val, "Integer", method, TRUE);
+  if (!mrb_obj_is_kind_of(mrb, v, mrb->fixnum_class)) {
+    mrb_raisef(mrb, E_TYPE_ERROR, "can't convert %S to Integer (%S#%S gives %S)",
+               val, val, mrb_str_new_cstr(mrb, method), v);
+  }
+  return v;
 }
 
 mrb_value
 mrb_to_int(mrb_state *mrb, mrb_value val)
 {
-    return mrb_to_integer(mrb, val, "to_int");
+  return mrb_to_integer(mrb, val, "to_int");
 }
 
 static mrb_value
@@ -529,7 +524,7 @@ mrb_convert_to_integer(mrb_state *mrb, mrb_value val, int base)
     case MRB_TT_FLOAT:
       if (base != 0) goto arg_error;
       if (FIXABLE(mrb_float(val))) {
-          break;
+        break;
       }
       return mrb_flo_to_fixnum(mrb, val);
 
@@ -545,14 +540,14 @@ string_conv:
       break;
   }
   if (base != 0) {
-      tmp = mrb_check_string_type(mrb, val);
-      if (!mrb_nil_p(tmp)) goto string_conv;
-    arg_error:
-      mrb_raise(mrb, E_ARGUMENT_ERROR, "base specified for non string value");
+    tmp = mrb_check_string_type(mrb, val);
+    if (!mrb_nil_p(tmp)) goto string_conv;
+arg_error:
+    mrb_raise(mrb, E_ARGUMENT_ERROR, "base specified for non string value");
   }
   tmp = convert_type(mrb, val, "Integer", "to_int", FALSE);
   if (mrb_nil_p(tmp)) {
-      return mrb_to_integer(mrb, val, "to_i");
+    return mrb_to_integer(mrb, val, "to_i");
   }
   return tmp;
 }
@@ -560,14 +555,14 @@ string_conv:
 mrb_value
 mrb_Integer(mrb_state *mrb, mrb_value val)
 {
-    return mrb_convert_to_integer(mrb, val, 0);
+  return mrb_convert_to_integer(mrb, val, 0);
 }
 
 mrb_value
 mrb_Float(mrb_state *mrb, mrb_value val)
 {
   if (mrb_nil_p(val)) {
-      mrb_raise(mrb, E_TYPE_ERROR, "can't convert nil into Float");
+    mrb_raise(mrb, E_TYPE_ERROR, "can't convert nil into Float");
   }
   switch (mrb_type(val)) {
     case MRB_TT_FIXNUM:
@@ -590,7 +585,7 @@ mrb_inspect(mrb_state *mrb, mrb_value obj)
   return mrb_obj_as_string(mrb, mrb_funcall(mrb, obj, "inspect", 0, 0));
 }
 
-int
+mrb_bool
 mrb_eql(mrb_state *mrb, mrb_value obj1, mrb_value obj2)
 {
   if (mrb_obj_eq(mrb, obj1, obj2)) return TRUE;
diff --git a/src/opcode.h b/src/opcode.h
index b4f843116..f87611119 100644
--- a/src/opcode.h
+++ b/src/opcode.h
@@ -17,27 +17,27 @@
 /*        Ax:OP =      25: 7        */
 /*   A:Bz:Cz:OP = 9:14: 2: 7        */
 
-#define GET_OPCODE(i) ((int)(((mrb_code)(i)) & 0x7f))
-#define GETARG_A(i)   ((int)((((mrb_code)(i)) >> 23) & 0x1ff))
-#define GETARG_B(i)   ((int)((((mrb_code)(i)) >> 14) & 0x1ff))
-#define GETARG_C(i)   ((int)((((mrb_code)(i)) >>  7) & 0x7f))
-#define GETARG_Bx(i)  ((int)((((mrb_code)(i)) >>  7) & 0xffff))
-#define GETARG_sBx(i) ((int)(GETARG_Bx(i)-MAXARG_sBx))
-#define GETARG_Ax(i)  ((int32_t)((((mrb_code)(i)) >>  7) & 0x1ffffff))
+#define GET_OPCODE(i)            ((int)(((mrb_code)(i)) & 0x7f))
+#define GETARG_A(i)              ((int)((((mrb_code)(i)) >> 23) & 0x1ff))
+#define GETARG_B(i)              ((int)((((mrb_code)(i)) >> 14) & 0x1ff))
+#define GETARG_C(i)              ((int)((((mrb_code)(i)) >>  7) & 0x7f))
+#define GETARG_Bx(i)             ((int)((((mrb_code)(i)) >>  7) & 0xffff))
+#define GETARG_sBx(i)            ((int)(GETARG_Bx(i)-MAXARG_sBx))
+#define GETARG_Ax(i)             ((int32_t)((((mrb_code)(i)) >>  7) & 0x1ffffff))
 #define GETARG_UNPACK_b(i,n1,n2) ((int)((((mrb_code)(i)) >> (7+(n2))) & (((1<<(n1))-1))))
 #define GETARG_UNPACK_c(i,n1,n2) ((int)((((mrb_code)(i)) >> 7) & (((1<<(n2))-1))))
-#define GETARG_b(i)   GETARG_UNPACK_b(i,14,2)
-#define GETARG_c(i)   GETARG_UNPACK_c(i,14,2)
-
-#define MKOPCODE(op)  ((op) & 0x7f)
-#define MKARG_A(c)    ((mrb_code)((c) & 0x1ff) << 23)
-#define MKARG_B(c)    ((mrb_code)((c) & 0x1ff) << 14)
-#define MKARG_C(c)    (((c) & 0x7f) <<  7)
-#define MKARG_Bx(v)   ((mrb_code)((v) & 0xffff) << 7)
-#define MKARG_sBx(v)  MKARG_Bx((v)+MAXARG_sBx)
-#define MKARG_Ax(v)   ((mrb_code)((v) & 0x1ffffff) << 7)
+#define GETARG_b(i)              GETARG_UNPACK_b(i,14,2)
+#define GETARG_c(i)              GETARG_UNPACK_c(i,14,2)
+
+#define MKOPCODE(op)          ((op) & 0x7f)
+#define MKARG_A(c)            ((mrb_code)((c) & 0x1ff) << 23)
+#define MKARG_B(c)            ((mrb_code)((c) & 0x1ff) << 14)
+#define MKARG_C(c)            (((c) & 0x7f) <<  7)
+#define MKARG_Bx(v)           ((mrb_code)((v) & 0xffff) << 7)
+#define MKARG_sBx(v)          MKARG_Bx((v)+MAXARG_sBx)
+#define MKARG_Ax(v)           ((mrb_code)((v) & 0x1ffffff) << 7)
 #define MKARG_PACK(b,n1,c,n2) ((((b) & ((1<<n1)-1)) << (7+n2))|(((c) & ((1<<n2)-1)) << 7))
-#define MKARG_bc(b,c) MKARG_PACK(b,14,c,2)
+#define MKARG_bc(b,c)         MKARG_PACK(b,14,c,2)
 
 #define MKOP_A(op,a)        (MKOPCODE(op)|MKARG_A(a))
 #define MKOP_AB(op,a,b)     (MKOP_A(op,a)|MKARG_B(b))
@@ -50,98 +50,101 @@
 #define MKOP_Abc(op,a,b,c)  (MKOP_A(op,a)|MKARG_bc(b,c))
 
 enum {
-OP_NOP=0,/*                                                             */
-OP_MOVE,/*      A B     R(A) := R(B)                                    */
-OP_LOADL,/*     A Bx    R(A) := Lit(Bx)                                 */
-OP_LOADI,/*     A sBx   R(A) := sBx                                     */
-OP_LOADSYM,/*   A Bx    R(A) := Sym(Bx)                                 */
-OP_LOADNIL,/*   A       R(A) := nil                                     */
-OP_LOADSELF,/*  A       R(A) := self                                    */
-OP_LOADT,/*     A       R(A) := true                                    */
-OP_LOADF,/*     A       R(A) := false                                   */
-
-OP_GETGLOBAL,/* A Bx    R(A) := getglobal(Sym(Bx))                      */
-OP_SETGLOBAL,/* A Bx    setglobal(Sym(Bx), R(A))                        */
-OP_GETSPECIAL,/*A Bx    R(A) := Special[Bx]                             */
-OP_SETSPECIAL,/*A Bx    Special[Bx] := R(A)                             */
-OP_GETIV,/*     A Bx    R(A) := ivget(Sym(Bx))                          */
-OP_SETIV,/*     A Bx    ivset(Sym(Bx),R(A))                             */
-OP_GETCV,/*     A Bx    R(A) := cvget(Sym(Bx))                          */
-OP_SETCV,/*     A Bx    cvset(Sym(Bx),R(A))                             */
-OP_GETCONST,/*  A Bx    R(A) := constget(Sym(Bx))                       */
-OP_SETCONST,/*  A Bx    constset(Sym(Bx),R(A))                          */
-OP_GETMCNST,/*  A Bx    R(A) := R(A)::Sym(B)                            */
-OP_SETMCNST,/*  A Bx    R(A+1)::Sym(B) := R(A)                          */
-OP_GETUPVAR,/*  A B C   R(A) := uvget(B,C)                              */
-OP_SETUPVAR,/*  A B C   uvset(B,C,R(A))                                 */
-
-OP_JMP,/*       sBx     pc+=sBx                                         */
-OP_JMPIF,/*     A sBx   if R(A) pc+=sBx                                 */
-OP_JMPNOT,/*    A sBx   if !R(A) pc+=sBx                                */
-OP_ONERR,/*     sBx     rescue_push(pc+sBx)                             */
-OP_RESCUE,/*    A       clear(exc); R(A) := exception (ignore when A=0) */
-OP_POPERR,/*    A       A.times{rescue_pop()}                           */
-OP_RAISE,/*     A       raise(R(A))                                     */
-OP_EPUSH,/*     Bx      ensure_push(SEQ[Bx])                            */
-OP_EPOP,/*      A       A.times{ensure_pop().call}                      */
-
-OP_SEND,/*      A B C   R(A) := call(R(A),mSym(B),R(A+1),...,R(A+C))    */
-OP_SENDB,/*     A B C   R(A) := call(R(A),mSym(B),R(A+1),...,R(A+C),&R(A+C+1))*/
-OP_FSEND,/*     A B C   R(A) := fcall(R(A),mSym(B),R(A+1),...,R(A+C-1)) */
-OP_CALL,/*      A B C   R(A) := self.call(R(A),.., R(A+C))              */
-OP_SUPER,/*     A B C   R(A) := super(R(A+1),... ,R(A+C-1))             */
-OP_ARGARY,/*    A Bx    R(A) := argument array (16=6:1:5:4)             */
-OP_ENTER,/*     Ax      arg setup according to flags (24=5:5:1:5:5:1:1) */
-OP_KARG,/*      A B C   R(A) := kdict[mSym(B)]; if C kdict.rm(mSym(B))  */
-OP_KDICT,/*     A C     R(A) := kdict                                   */
-
-OP_RETURN,/*    A B     return R(A) (B=normal,in-block return/break)    */
-OP_TAILCALL,/*  A B C   return call(R(A),mSym(B),*R(C))                 */
-OP_BLKPUSH,/*   A Bx    R(A) := block (16=6:1:5:4)                      */
-
-OP_ADD,/*       A B C   R(A) := R(A)+R(A+1) (mSyms[B]=:+,C=1)           */
-OP_ADDI,/*      A B C   R(A) := R(A)+C (mSyms[B]=:+)                    */
-OP_SUB,/*       A B C   R(A) := R(A)-R(A+1) (mSyms[B]=:-,C=1)           */
-OP_SUBI,/*      A B C   R(A) := R(A)-C (mSyms[B]=:-)                    */
-OP_MUL,/*       A B C   R(A) := R(A)*R(A+1) (mSyms[B]=:*,C=1)           */
-OP_DIV,/*       A B C   R(A) := R(A)/R(A+1) (mSyms[B]=:/,C=1)           */
-OP_EQ,/*        A B C   R(A) := R(A)==R(A+1) (mSyms[B]=:==,C=1)         */
-OP_LT,/*        A B C   R(A) := R(A)<R(A+1)  (mSyms[B]=:<,C=1)          */
-OP_LE,/*        A B C   R(A) := R(A)<=R(A+1) (mSyms[B]=:<=,C=1)         */
-OP_GT,/*        A B C   R(A) := R(A)>R(A+1)  (mSyms[B]=:>,C=1)          */
-OP_GE,/*        A B C   R(A) := R(A)>=R(A+1) (mSyms[B]=:>=,C=1)         */
-
-OP_ARRAY,/*     A B C   R(A) := ary_new(R(B),R(B+1)..R(B+C))            */
-OP_ARYCAT,/*    A B     ary_cat(R(A),R(B))                              */
-OP_ARYPUSH,/*   A B     ary_push(R(A),R(B))                             */
-OP_AREF,/*      A B C   R(A) := R(B)[C]                                 */
-OP_ASET,/*      A B C   R(B)[C] := R(A)                                 */
-OP_APOST,/*     A B C   *R(A),R(A+1)..R(A+C) := R(A)                    */
-
-OP_STRING,/*    A Bx    R(A) := str_dup(Lit(Bx))                        */
-OP_STRCAT,/*    A B     str_cat(R(A),R(B))                              */
-
-OP_HASH,/*      A B C   R(A) := hash_new(R(B),R(B+1)..R(B+C))           */
-OP_LAMBDA,/*    A Bz Cz R(A) := lambda(SEQ[Bz],Cm)                      */
-OP_RANGE,/*     A B C   R(A) := range_new(R(B),R(B+1),C)                */
-
-OP_OCLASS,/*    A       R(A) := ::Object                                */
-OP_CLASS,/*     A B     R(A) := newclass(R(A),mSym(B),R(A+1))           */
-OP_MODULE,/*    A B     R(A) := newmodule(R(A),mSym(B))                 */
-OP_EXEC,/*      A Bx    R(A) := blockexec(R(A),SEQ[Bx])                 */
-OP_METHOD,/*    A B     R(A).newmethod(mSym(B),R(A+1))                  */
-OP_SCLASS,/*    A B     R(A) := R(B).singleton_class                    */
-OP_TCLASS,/*    A       R(A) := target_class                            */
-
-OP_DEBUG,/*     A       print R(A)                                      */
-OP_STOP,/*              stop VM                                         */
-OP_ERR,/*       Bx      raise RuntimeError with message Lit(Bx)         */
-
-OP_RSVD1,/*             reserved instruction #1                         */
-OP_RSVD2,/*             reserved instruction #2                         */
-OP_RSVD3,/*             reserved instruction #3                         */
-OP_RSVD4,/*             reserved instruction #4                         */
-OP_RSVD5,/*             reserved instruction #5                         */
+  /*-----------------------------------------------------------------------
+  operation code  operand description
+  ------------------------------------------------------------------------*/
+  OP_NOP=0,/*                                                             */
+  OP_MOVE,/*      A B     R(A) := R(B)                                    */
+  OP_LOADL,/*     A Bx    R(A) := Lit(Bx)                                 */
+  OP_LOADI,/*     A sBx   R(A) := sBx                                     */
+  OP_LOADSYM,/*   A Bx    R(A) := Sym(Bx)                                 */
+  OP_LOADNIL,/*   A       R(A) := nil                                     */
+  OP_LOADSELF,/*  A       R(A) := self                                    */
+  OP_LOADT,/*     A       R(A) := true                                    */
+  OP_LOADF,/*     A       R(A) := false                                   */
+
+  OP_GETGLOBAL,/* A Bx    R(A) := getglobal(Sym(Bx))                      */
+  OP_SETGLOBAL,/* A Bx    setglobal(Sym(Bx), R(A))                        */
+  OP_GETSPECIAL,/*A Bx    R(A) := Special[Bx]                             */
+  OP_SETSPECIAL,/*A Bx    Special[Bx] := R(A)                             */
+  OP_GETIV,/*     A Bx    R(A) := ivget(Sym(Bx))                          */
+  OP_SETIV,/*     A Bx    ivset(Sym(Bx),R(A))                             */
+  OP_GETCV,/*     A Bx    R(A) := cvget(Sym(Bx))                          */
+  OP_SETCV,/*     A Bx    cvset(Sym(Bx),R(A))                             */
+  OP_GETCONST,/*  A Bx    R(A) := constget(Sym(Bx))                       */
+  OP_SETCONST,/*  A Bx    constset(Sym(Bx),R(A))                          */
+  OP_GETMCNST,/*  A Bx    R(A) := R(A)::Sym(B)                            */
+  OP_SETMCNST,/*  A Bx    R(A+1)::Sym(B) := R(A)                          */
+  OP_GETUPVAR,/*  A B C   R(A) := uvget(B,C)                              */
+  OP_SETUPVAR,/*  A B C   uvset(B,C,R(A))                                 */
+
+  OP_JMP,/*       sBx     pc+=sBx                                         */
+  OP_JMPIF,/*     A sBx   if R(A) pc+=sBx                                 */
+  OP_JMPNOT,/*    A sBx   if !R(A) pc+=sBx                                */
+  OP_ONERR,/*     sBx     rescue_push(pc+sBx)                             */
+  OP_RESCUE,/*    A       clear(exc); R(A) := exception (ignore when A=0) */
+  OP_POPERR,/*    A       A.times{rescue_pop()}                           */
+  OP_RAISE,/*     A       raise(R(A))                                     */
+  OP_EPUSH,/*     Bx      ensure_push(SEQ[Bx])                            */
+  OP_EPOP,/*      A       A.times{ensure_pop().call}                      */
+
+  OP_SEND,/*      A B C   R(A) := call(R(A),mSym(B),R(A+1),...,R(A+C))    */
+  OP_SENDB,/*     A B C   R(A) := call(R(A),mSym(B),R(A+1),...,R(A+C),&R(A+C+1))*/
+  OP_FSEND,/*     A B C   R(A) := fcall(R(A),mSym(B),R(A+1),...,R(A+C-1)) */
+  OP_CALL,/*      A B C   R(A) := self.call(R(A),.., R(A+C))              */
+  OP_SUPER,/*     A B C   R(A) := super(R(A+1),... ,R(A+C-1))             */
+  OP_ARGARY,/*    A Bx    R(A) := argument array (16=6:1:5:4)             */
+  OP_ENTER,/*     Ax      arg setup according to flags (24=5:5:1:5:5:1:1) */
+  OP_KARG,/*      A B C   R(A) := kdict[mSym(B)]; if C kdict.rm(mSym(B))  */
+  OP_KDICT,/*     A C     R(A) := kdict                                   */
+
+  OP_RETURN,/*    A B     return R(A) (B=normal,in-block return/break)    */
+  OP_TAILCALL,/*  A B C   return call(R(A),mSym(B),*R(C))                 */
+  OP_BLKPUSH,/*   A Bx    R(A) := block (16=6:1:5:4)                      */
+
+  OP_ADD,/*       A B C   R(A) := R(A)+R(A+1) (mSyms[B]=:+,C=1)           */
+  OP_ADDI,/*      A B C   R(A) := R(A)+C (mSyms[B]=:+)                    */
+  OP_SUB,/*       A B C   R(A) := R(A)-R(A+1) (mSyms[B]=:-,C=1)           */
+  OP_SUBI,/*      A B C   R(A) := R(A)-C (mSyms[B]=:-)                    */
+  OP_MUL,/*       A B C   R(A) := R(A)*R(A+1) (mSyms[B]=:*,C=1)           */
+  OP_DIV,/*       A B C   R(A) := R(A)/R(A+1) (mSyms[B]=:/,C=1)           */
+  OP_EQ,/*        A B C   R(A) := R(A)==R(A+1) (mSyms[B]=:==,C=1)         */
+  OP_LT,/*        A B C   R(A) := R(A)<R(A+1)  (mSyms[B]=:<,C=1)          */
+  OP_LE,/*        A B C   R(A) := R(A)<=R(A+1) (mSyms[B]=:<=,C=1)         */
+  OP_GT,/*        A B C   R(A) := R(A)>R(A+1)  (mSyms[B]=:>,C=1)          */
+  OP_GE,/*        A B C   R(A) := R(A)>=R(A+1) (mSyms[B]=:>=,C=1)         */
+
+  OP_ARRAY,/*     A B C   R(A) := ary_new(R(B),R(B+1)..R(B+C))            */
+  OP_ARYCAT,/*    A B     ary_cat(R(A),R(B))                              */
+  OP_ARYPUSH,/*   A B     ary_push(R(A),R(B))                             */
+  OP_AREF,/*      A B C   R(A) := R(B)[C]                                 */
+  OP_ASET,/*      A B C   R(B)[C] := R(A)                                 */
+  OP_APOST,/*     A B C   *R(A),R(A+1)..R(A+C) := R(A)                    */
+
+  OP_STRING,/*    A Bx    R(A) := str_dup(Lit(Bx))                        */
+  OP_STRCAT,/*    A B     str_cat(R(A),R(B))                              */
+
+  OP_HASH,/*      A B C   R(A) := hash_new(R(B),R(B+1)..R(B+C))           */
+  OP_LAMBDA,/*    A Bz Cz R(A) := lambda(SEQ[Bz],Cm)                      */
+  OP_RANGE,/*     A B C   R(A) := range_new(R(B),R(B+1),C)                */
+
+  OP_OCLASS,/*    A       R(A) := ::Object                                */
+  OP_CLASS,/*     A B     R(A) := newclass(R(A),mSym(B),R(A+1))           */
+  OP_MODULE,/*    A B     R(A) := newmodule(R(A),mSym(B))                 */
+  OP_EXEC,/*      A Bx    R(A) := blockexec(R(A),SEQ[Bx])                 */
+  OP_METHOD,/*    A B     R(A).newmethod(mSym(B),R(A+1))                  */
+  OP_SCLASS,/*    A B     R(A) := R(B).singleton_class                    */
+  OP_TCLASS,/*    A       R(A) := target_class                            */
+
+  OP_DEBUG,/*     A       print R(A)                                      */
+  OP_STOP,/*              stop VM                                         */
+  OP_ERR,/*       Bx      raise RuntimeError with message Lit(Bx)         */
+
+  OP_RSVD1,/*             reserved instruction #1                         */
+  OP_RSVD2,/*             reserved instruction #2                         */
+  OP_RSVD3,/*             reserved instruction #3                         */
+  OP_RSVD4,/*             reserved instruction #4                         */
+  OP_RSVD5,/*             reserved instruction #5                         */
 };
 
 #define OP_L_STRICT  1
diff --git a/src/parse.y b/src/parse.y
index f5dbdb6fd..9a83d5cbd 100644
--- a/src/parse.y
+++ b/src/parse.y
@@ -1,6 +1,6 @@
 /*
 ** parse.y - mruby parser
-** 
+**
 ** See Copyright Notice in mruby.h
 */
 
@@ -272,7 +272,7 @@ new_scope(parser_state *p, node *body)
 static node*
 new_begin(parser_state *p, node *body)
 {
-  if (body) 
+  if (body)
     return list2((node*)NODE_BEGIN, body);
   return cons((node*)NODE_BEGIN, 0);
 }
@@ -909,7 +909,7 @@ parsing_heredoc_inf(parser_state *p)
   node *nd = p->parsing_heredoc;
   if (nd == NULL)
     return NULL;
-  /* assert(nd->car->car == NODE_HEREDOC); */
+  /* mrb_assert(nd->car->car == NODE_HEREDOC); */
   return (parser_heredoc_info*)nd->car->cdr;
 }
 
@@ -2744,7 +2744,7 @@ var_ref		: variable
 		    {
 		      $$ = var_reference(p, $1);
 		    }
-		| keyword_nil 
+		| keyword_nil
 		    {
 		      $$ = new_nil(p);
 		    }
@@ -3293,7 +3293,7 @@ peek_n(parser_state *p, int c, int n)
     list = push(list, (node*)(intptr_t)c0);
   } while(n--);
   if (p->pb) {
-    p->pb = push(p->pb, (node*)list);
+    p->pb = append(p->pb, (node*)list);
   }
   else {
     p->pb = list;
@@ -3408,7 +3408,7 @@ scan_oct(const int *start, int len, int *retlen)
   const int *s = start;
   int retval = 0;
 
-  /* assert(len <= 3) */
+  /* mrb_assert(len <= 3) */
   while (len-- && *s >= '0' && *s <= '7') {
     retval <<= 3;
     retval |= *s++ - '0';
@@ -3426,7 +3426,7 @@ scan_hex(const int *start, int len, int *retlen)
   register int retval = 0;
   char *tmp;
 
-  /* assert(len <= 2) */
+  /* mrb_assert(len <= 2) */
   while (len-- && *s && (tmp = (char*)strchr(hexdigit, *s))) {
     retval <<= 4;
     retval |= (tmp - hexdigit) & 15;
@@ -3620,12 +3620,14 @@ parse_string(parser_state *p)
 	  tokadd(p, '\n');
 	}
 	else {
-	  pushback(p, c);
-
-	  if(type & STR_FUNC_REGEXP)
+	  if (type & STR_FUNC_REGEXP) {
 	    tokadd(p, '\\');
-
-	  tokadd(p, read_escape(p));
+	    if (c != -1)
+	      tokadd(p, c);
+	  } else {
+	    pushback(p, c);
+	    tokadd(p, read_escape(p));
+	  }
 	  if (hinf)
 	    hinf->line_head = FALSE;
 	}
@@ -3684,7 +3686,7 @@ parse_string(parser_state *p)
 
     tokadd(p, c);
 
-  } 
+  }
 
   tokfix(p);
   p->lstate = EXPR_END;
@@ -3729,7 +3731,7 @@ parse_string(parser_state *p)
   yylval.nd = new_str(p, tok(p), toklen(p));
   return tSTRING;
 }
- 
+
 
 static int
 heredoc_identifier(parser_state *p)
@@ -4811,7 +4813,7 @@ parser_yylex(parser_state *p)
       pushback(p, c);
       if (last_state == EXPR_FNAME) goto gvar;
       tokfix(p);
-      yylval.nd = new_nth_ref(p, atoi(tok(p))); 
+      yylval.nd = new_nth_ref(p, atoi(tok(p)));
       return tNTH_REF;
 
     default:
@@ -5174,7 +5176,7 @@ parser_state*
 mrb_parse_file(mrb_state *mrb, FILE *f, mrbc_context *c)
 {
   parser_state *p;
- 
+
   p = mrb_parser_new(mrb);
   if (!p) return 0;
   p->s = p->send = NULL;
@@ -5559,7 +5561,7 @@ parser_dump(mrb_state *mrb, node *tree, int offset)
     printf("NODE_CALL:\n");
     parser_dump(mrb, tree->car, offset+1);
     dump_prefix(offset+1);
-    printf("method='%s' (%d)\n", 
+    printf("method='%s' (%d)\n",
     mrb_sym2name(mrb, sym(tree->cdr->car)),
     (int)(intptr_t)tree->cdr->car);
     tree = tree->cdr->cdr->car;
diff --git a/src/pool.c b/src/pool.c
index c992b5e53..f09df92c5 100644
--- a/src/pool.c
+++ b/src/pool.c
@@ -53,7 +53,7 @@ mrb_pool_open(mrb_state *mrb)
 
   if (pool) {
     pool->mrb = mrb;
-    pool->pages = 0;
+    pool->pages = NULL;
   }
 
   return pool;
@@ -96,7 +96,7 @@ mrb_pool_alloc(mrb_pool *pool, size_t len)
   struct mrb_pool_page *page;
   size_t n;
 
-  if (!pool) return 0;
+  if (!pool) return NULL;
   len += ALIGN_PADDING(len);
   page = pool->pages;
   while (page) {
@@ -109,7 +109,7 @@ mrb_pool_alloc(mrb_pool *pool, size_t len)
     page = page->next;
   }
   page = page_alloc(pool, len);
-  if (!page) return 0;
+  if (!page) return NULL;
   page->offset = len;
   page->next = pool->pages;
   pool->pages = page;
@@ -118,7 +118,7 @@ mrb_pool_alloc(mrb_pool *pool, size_t len)
   return page->last;
 }
 
-int
+mrb_bool
 mrb_pool_can_realloc(mrb_pool *pool, void *p, size_t len)
 {
   struct mrb_pool_page *page;
@@ -145,7 +145,7 @@ mrb_pool_realloc(mrb_pool *pool, void *p, size_t oldlen, size_t newlen)
   struct mrb_pool_page *page;
   void *np;
 
-  if (!pool) return 0;
+  if (!pool) return NULL;
   oldlen += ALIGN_PADDING(oldlen);
   newlen += ALIGN_PADDING(newlen);
   page = pool->pages;
@@ -177,10 +177,10 @@ main(void)
   mrb_pool *pool;
   void *p;
 
-  pool = mrb_pool_open(0);
+  pool = mrb_pool_open(NULL);
   p = mrb_pool_alloc(pool, len);
   for (i=1; i<20; i++) {
-    printf("%p (len=%d) %d\n", p, len, mrb_pool_can_realloc(pool, p, len*2));
+    printf("%p (len=%d) %ud\n", p, len, mrb_pool_can_realloc(pool, p, len*2));
     p = mrb_pool_realloc(pool, p, len, len*2);
     len *= 2;
   }
diff --git a/src/proc.c b/src/proc.c
index 5c50effaa..787a46492 100644
--- a/src/proc.c
+++ b/src/proc.c
@@ -139,7 +139,7 @@ mrb_proc_arity(mrb_state *mrb, mrb_value self)
   mrb_code *iseq = mrb_proc_iseq(mrb, p);
   mrb_aspec aspec = GETARG_Ax(*iseq);
   int ma, ra, pa, arity;
-  
+
   ma = MRB_ASPEC_REQ(aspec);
   ra = MRB_ASPEC_REST(aspec);
   pa = MRB_ASPEC_POST(aspec);
@@ -201,8 +201,8 @@ mrb_init_proc(mrb_state *mrb)
   mrb_define_method(mrb, mrb->proc_class, "arity", mrb_proc_arity, MRB_ARGS_NONE());
 
   m = mrb_proc_new(mrb, call_irep);
-  mrb_define_method_raw(mrb, mrb->proc_class, mrb_intern(mrb, "call"), m);
-  mrb_define_method_raw(mrb, mrb->proc_class, mrb_intern(mrb, "[]"), m);
+  mrb_define_method_raw(mrb, mrb->proc_class, mrb_intern2(mrb, "call", 4), m);
+  mrb_define_method_raw(mrb, mrb->proc_class, mrb_intern2(mrb, "[]", 2), m);
 
   mrb_define_class_method(mrb, mrb->kernel_module, "lambda", proc_lambda, MRB_ARGS_NONE()); /* 15.3.1.2.6  */
   mrb_define_method(mrb, mrb->kernel_module,       "lambda", proc_lambda, MRB_ARGS_NONE()); /* 15.3.1.3.27 */
diff --git a/src/range.c b/src/range.c
index 10a03ddb4..1d6519a6e 100644
--- a/src/range.c
+++ b/src/range.c
@@ -152,33 +152,25 @@ mrb_range_eq(mrb_state *mrb, mrb_value range)
   struct RRange *rr;
   struct RRange *ro;
   mrb_value obj;
-  mrb_bool eq_p;
 
   mrb_get_args(mrb, "o", &obj);
 
-  if (mrb_obj_equal(mrb, range, obj)) {
-    eq_p = 1;
-  }
-  else if (!mrb_obj_is_instance_of(mrb, obj, mrb_obj_class(mrb, range))) { /* same class? */
-    eq_p = 0;
-  }
-  else {
-    rr = mrb_range_ptr(range);
-    ro = mrb_range_ptr(obj);
-    if (!mrb_obj_equal(mrb, rr->edges->beg, ro->edges->beg) ||
-        !mrb_obj_equal(mrb, rr->edges->end, ro->edges->end) ||
-        rr->excl != ro->excl) {
-      eq_p = 0;
-    }
-    else {
-      eq_p = 1;
-    }
+  if (mrb_obj_equal(mrb, range, obj)) return mrb_true_value();
+  if (!mrb_obj_is_instance_of(mrb, obj, mrb_obj_class(mrb, range))) { /* same class? */
+    return mrb_false_value();
   }
 
-  return mrb_bool_value(eq_p);
+  rr = mrb_range_ptr(range);
+  ro = mrb_range_ptr(obj);
+  if (!mrb_bool(mrb_funcall(mrb, rr->edges->beg, "==", 1, ro->edges->beg)) ||
+      !mrb_bool(mrb_funcall(mrb, rr->edges->end, "==", 1, ro->edges->end)) ||
+      rr->excl != ro->excl) {
+    return mrb_false_value();
+  }
+  return mrb_true_value();
 }
 
-static int
+static mrb_bool
 r_le(mrb_state *mrb, mrb_value a, mrb_value b)
 {
   mrb_value r = mrb_funcall(mrb, a, "<=>", 1, b); /* compare result */
@@ -192,7 +184,7 @@ r_le(mrb_state *mrb, mrb_value a, mrb_value b)
   return FALSE;
 }
 
-static int
+static mrb_bool
 r_gt(mrb_state *mrb, mrb_value a, mrb_value b)
 {
   mrb_value r = mrb_funcall(mrb, a, "<=>", 1, b);
@@ -205,7 +197,7 @@ r_gt(mrb_state *mrb, mrb_value a, mrb_value b)
   return FALSE;
 }
 
-static int
+static mrb_bool
 r_ge(mrb_state *mrb, mrb_value a, mrb_value b)
 {
   mrb_value r = mrb_funcall(mrb, a, "<=>", 1, b); /* compare result */
@@ -284,10 +276,10 @@ mrb_range_beg_len(mrb_state *mrb, mrb_value range, mrb_int *begp, mrb_int *lenp,
 
   if (beg < 0) {
     beg += len;
-    if (beg < 0) goto out_of_range;
+    if (beg < 0) return FALSE;
   }
 
-  if (beg > len) goto out_of_range;
+  if (beg > len) return FALSE;
   if (end > len) end = len;
 
   if (end < 0) end += len;
@@ -298,9 +290,6 @@ mrb_range_beg_len(mrb_state *mrb, mrb_value range, mrb_int *begp, mrb_int *lenp,
   *begp = beg;
   *lenp = len;
   return TRUE;
-
-out_of_range:
-  return FALSE;
 }
 
 /* 15.2.14.4.12(x) */
@@ -385,34 +374,23 @@ range_eql(mrb_state *mrb, mrb_value range)
 {
   mrb_value obj;
   struct RRange *r, *o;
-  mrb_bool eql_p;
 
   mrb_get_args(mrb, "o", &obj);
-  if (mrb_obj_equal(mrb, range, obj)) {
-    eql_p = 1;
-  }
-  else if (!mrb_obj_is_kind_of(mrb, obj, RANGE_CLASS)) {
-    eql_p = 0;
+
+  if (mrb_obj_equal(mrb, range, obj)) return mrb_true_value();
+  if (!mrb_obj_is_kind_of(mrb, obj, RANGE_CLASS)) {
+    return mrb_false_value();
   }
-  else {
-    r = mrb_range_ptr(range);
-    if (mrb_type(obj) != MRB_TT_RANGE) {
-      eql_p = 0;
-    }
-    else {
-      o = mrb_range_ptr(obj);
-      if (!mrb_eql(mrb, r->edges->beg, o->edges->beg) ||
-          !mrb_eql(mrb, r->edges->end, o->edges->end) ||
-          (r->excl != o->excl)) {
-        eql_p = 0;
-      }
-      else {
-        eql_p = 1;
-      }
-    }
+  if (mrb_type(obj) != MRB_TT_RANGE) return mrb_false_value();
+
+  r = mrb_range_ptr(range);
+  o = mrb_range_ptr(obj);
+  if (!mrb_eql(mrb, r->edges->beg, o->edges->beg) ||
+      !mrb_eql(mrb, r->edges->end, o->edges->end) ||
+      (r->excl != o->excl)) {
+    return mrb_false_value();
   }
-
-  return mrb_bool_value(eql_p);
+  return mrb_true_value();
 }
 
 /* 15.2.14.4.15(x) */
diff --git a/src/re.h b/src/re.h
index 5632bc399..20cd0b226 100644
--- a/src/re.h
+++ b/src/re.h
@@ -7,6 +7,7 @@
 #ifndef RE_H
 #define RE_H
 
-#define REGEXP_CLASS "Regexp"
+#define REGEXP_CLASS          "Regexp"
+#define REGEXP_CLASS_CSTR_LEN 6
 
 #endif
diff --git a/src/state.c b/src/state.c
index 34de1e45e..5dcc4a40a 100644
--- a/src/state.c
+++ b/src/state.c
@@ -21,10 +21,6 @@ inspect_main(mrb_state *mrb, mrb_value mod)
   return mrb_str_new(mrb, "main", 4);
 }
 
-#ifdef MRB_NAN_BOXING
-#include <assert.h>
-#endif
-
 mrb_state*
 mrb_open_allocf(mrb_allocf f, void *ud)
 {
@@ -33,7 +29,7 @@ mrb_open_allocf(mrb_allocf f, void *ud)
   mrb_state *mrb;
 
 #ifdef MRB_NAN_BOXING
-  assert(sizeof(void*) == 4);
+  mrb_assert(sizeof(void*) == 4);
 #endif
 
   mrb = (mrb_state *)(f)(NULL, NULL, sizeof(mrb_state), ud);
@@ -192,7 +188,7 @@ mrb_value
 mrb_top_self(mrb_state *mrb)
 {
   if (!mrb->top_self) {
-    mrb->top_self = (struct RObject*)mrb_obj_alloc(mrb, MRB_TT_OBJECT, mrb->object_class);  
+    mrb->top_self = (struct RObject*)mrb_obj_alloc(mrb, MRB_TT_OBJECT, mrb->object_class);
     mrb_define_singleton_method(mrb, mrb->top_self, "inspect", inspect_main, MRB_ARGS_NONE());
     mrb_define_singleton_method(mrb, mrb->top_self, "to_s", inspect_main, MRB_ARGS_NONE());
   }
diff --git a/src/string.c b/src/string.c
index 7cd727806..f3a788df3 100644
--- a/src/string.c
+++ b/src/string.c
@@ -74,7 +74,7 @@ mrb_str_modify(mrb_state *mrb, struct RString *s)
       if (p) {
         memcpy(ptr, p, len);
       }
-      ptr[len] = 0;
+      ptr[len] =  '\0';
       s->ptr = ptr;
       s->aux.capa = len;
       str_decref(mrb, shared);
@@ -104,10 +104,9 @@ mrb_str_resize(mrb_state *mrb, mrb_value str, mrb_int len)
   mrb_str_modify(mrb, s);
   slen = s->len;
   if (len != slen) {
-    if (slen < len || slen -len > 1024) {
-      s->ptr = (char *)mrb_realloc(mrb, s->ptr, len+1);
+    if (slen < len || slen - len > 256) {
+      RESIZE_CAPA(s, len);
     }
-    s->aux.capa = len;
     s->len = len;
     s->ptr[len] = '\0';   /* sentinel */
   }
@@ -261,14 +260,7 @@ mrb_str_new_cstr(mrb_state *mrb, const char *p)
     len = 0;
   }
 
-  s = mrb_obj_alloc_string(mrb);
-  s->ptr = (char *)mrb_malloc(mrb, len+1);
-  if (p) {
-    memcpy(s->ptr, p, len);
-  }
-  s->ptr[len] = 0;
-  s->len = (mrb_int)len;
-  s->aux.capa = (mrb_int)len;
+  s = str_new(mrb, p, len);
 
   return mrb_obj_value(s);
 }
@@ -406,7 +398,7 @@ mrb_str_concat(mrb_state *mrb, mrb_value self, mrb_value other)
   }
   memcpy(s1->ptr+s1->len, s2->ptr, s2->len);
   s1->len = len;
-  s1->ptr[len] = 0;
+  s1->ptr[len] =  '\0';
 }
 
 /*
@@ -603,7 +595,7 @@ mrb_str_cmp_m(mrb_state *mrb, mrb_value str1)
   return mrb_fixnum_value(result);
 }
 
-static int
+static mrb_bool
 str_eql(mrb_state *mrb, const mrb_value str1, const mrb_value str2)
 {
   const mrb_int len = RSTRING_LEN(str1);
@@ -614,7 +606,7 @@ str_eql(mrb_state *mrb, const mrb_value str1, const mrb_value str2)
   return FALSE;
 }
 
-int
+mrb_bool
 mrb_str_equal(mrb_state *mrb, mrb_value str1, mrb_value str2)
 {
   if (mrb_obj_equal(mrb, str1, str2)) return TRUE;
@@ -2542,7 +2534,6 @@ mrb_init_string(mrb_state *mrb)
   mrb_define_method(mrb, s, "*",               mrb_str_times,           MRB_ARGS_REQ(1)); /* 15.2.10.5.1  */
   mrb_define_method(mrb, s, "<=>",             mrb_str_cmp_m,           MRB_ARGS_REQ(1)); /* 15.2.10.5.3  */
   mrb_define_method(mrb, s, "==",              mrb_str_equal_m,         MRB_ARGS_REQ(1)); /* 15.2.10.5.4  */
-  mrb_define_method(mrb, s, "=~",              noregexp,                MRB_ARGS_REQ(1)); /* 15.2.10.5.5  */
   mrb_define_method(mrb, s, "[]",              mrb_str_aref_m,          MRB_ARGS_ANY());  /* 15.2.10.5.6  */
   mrb_define_method(mrb, s, "capitalize",      mrb_str_capitalize,      MRB_ARGS_NONE()); /* 15.2.10.5.7  */
   mrb_define_method(mrb, s, "capitalize!",     mrb_str_capitalize_bang, MRB_ARGS_REQ(1)); /* 15.2.10.5.8  */
@@ -2555,26 +2546,18 @@ mrb_init_string(mrb_state *mrb)
   mrb_define_method(mrb, s, "empty?",          mrb_str_empty_p,         MRB_ARGS_NONE()); /* 15.2.10.5.16 */
   mrb_define_method(mrb, s, "eql?",            mrb_str_eql,             MRB_ARGS_REQ(1)); /* 15.2.10.5.17 */
 
-  // NOTE: Regexp not implemented
-  mrb_define_method(mrb, s, "gsub",            noregexp,                MRB_ARGS_REQ(1)); /* 15.2.10.5.18 */
-  mrb_define_method(mrb, s, "gsub!",           noregexp,                MRB_ARGS_REQ(1)); /* 15.2.10.5.19 */
-
   mrb_define_method(mrb, s, "hash",            mrb_str_hash_m,          MRB_ARGS_REQ(1)); /* 15.2.10.5.20 */
   mrb_define_method(mrb, s, "include?",        mrb_str_include,         MRB_ARGS_REQ(1)); /* 15.2.10.5.21 */
   mrb_define_method(mrb, s, "index",           mrb_str_index_m,         MRB_ARGS_ANY());  /* 15.2.10.5.22 */
   mrb_define_method(mrb, s, "initialize",      mrb_str_init,            MRB_ARGS_REQ(1)); /* 15.2.10.5.23 */
   mrb_define_method(mrb, s, "initialize_copy", mrb_str_replace,         MRB_ARGS_REQ(1)); /* 15.2.10.5.24 */
   mrb_define_method(mrb, s, "intern",          mrb_str_intern,          MRB_ARGS_NONE()); /* 15.2.10.5.25 */
-  mrb_define_method(mrb, s, "match",           noregexp,                MRB_ARGS_REQ(1)); /* 15.2.10.5.27 */
   mrb_define_method(mrb, s, "replace",         mrb_str_replace,         MRB_ARGS_REQ(1)); /* 15.2.10.5.28 */
   mrb_define_method(mrb, s, "reverse",         mrb_str_reverse,         MRB_ARGS_NONE()); /* 15.2.10.5.29 */
   mrb_define_method(mrb, s, "reverse!",        mrb_str_reverse_bang,    MRB_ARGS_NONE()); /* 15.2.10.5.30 */
   mrb_define_method(mrb, s, "rindex",          mrb_str_rindex_m,        MRB_ARGS_ANY());  /* 15.2.10.5.31 */
-  mrb_define_method(mrb, s, "scan",            noregexp,                MRB_ARGS_REQ(1)); /* 15.2.10.5.32 */
   mrb_define_method(mrb, s, "slice",           mrb_str_aref_m,          MRB_ARGS_ANY());  /* 15.2.10.5.34 */
   mrb_define_method(mrb, s, "split",           mrb_str_split_m,         MRB_ARGS_ANY());  /* 15.2.10.5.35 */
-  mrb_define_method(mrb, s, "sub",             noregexp,                MRB_ARGS_REQ(1)); /* 15.2.10.5.36 */
-  mrb_define_method(mrb, s, "sub!",            noregexp,                MRB_ARGS_REQ(1)); /* 15.2.10.5.37 */
 
   mrb_define_method(mrb, s, "to_i",            mrb_str_to_i,            MRB_ARGS_ANY());  /* 15.2.10.5.38 */
   mrb_define_method(mrb, s, "to_f",            mrb_str_to_f,            MRB_ARGS_NONE()); /* 15.2.10.5.39 */
diff --git a/src/symbol.c b/src/symbol.c
index c0bb48f32..c145a4a1a 100644
--- a/src/symbol.c
+++ b/src/symbol.c
@@ -251,7 +251,7 @@ sym_to_sym(mrb_state *mrb, mrb_value sym)
 #endif
 #define is_identchar(c) (SIGN_EXTEND_CHAR(c)!=-1&&(ISALNUM(c) || (c) == '_'))
 
-static int
+static mrb_bool
 is_special_global_name(const char* m)
 {
   switch (*m) {
@@ -274,7 +274,7 @@ is_special_global_name(const char* m)
   return !*m;
 }
 
-static int
+static mrb_bool
 symname_p(const char *name)
 {
   const char *m = name;
@@ -382,7 +382,7 @@ mrb_sym2str(mrb_state *mrb, mrb_sym sym)
   size_t len;
   const char *name = mrb_sym2name_len(mrb, sym, &len);
   mrb_value str;
-  
+
   if (!name) return mrb_undef_value(); /* can't happen */
   str = mrb_str_new_static(mrb, name, len);
   if (symname_p(name) && strlen(name) == len) {
@@ -452,5 +452,5 @@ mrb_init_symbol(mrb_state *mrb)
   mrb_define_method(mrb, sym, "to_sym",          sym_to_sym,     MRB_ARGS_NONE());              /* 15.2.11.3.4  */
   mrb_define_method(mrb, sym, "inspect",         sym_inspect,    MRB_ARGS_NONE());              /* 15.2.11.3.5(x)  */
   mrb_define_method(mrb, sym, "<=>",             sym_cmp,        MRB_ARGS_REQ(1));
-  mrb->init_sym = mrb_intern(mrb, "initialize");
+  mrb->init_sym = mrb_intern2(mrb, "initialize", 10);
 }
diff --git a/src/variable.c b/src/variable.c
index 2610c5d7a..048b63bca 100644
--- a/src/variable.c
+++ b/src/variable.c
@@ -27,12 +27,21 @@ typedef struct segment {
   struct segment *next;
 } segment;
 
+/* Instance variable table structure */
 typedef struct iv_tbl {
   segment *rootseg;
   size_t size;
   size_t last_len;
 } iv_tbl;
 
+/*
+ * Creates the instance variable table.
+ *
+ * Parameters
+ *   mrb
+ * Returns
+ *   the instance variable table.
+ */
 static iv_tbl*
 iv_new(mrb_state *mrb)
 {
@@ -47,6 +56,15 @@ iv_new(mrb_state *mrb)
   return t;
 }
 
+/*
+ * Set the value for the symbol in the instance variable table.
+ *
+ * Parameters
+ *   mrb
+ *   t     the instance variable table to be set in.
+ *   sym   the symbol to be used as the key.
+ *   val   the value to be set.
+ */
 static void
 iv_put(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value val)
 {
@@ -59,7 +77,7 @@ iv_put(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value val)
   while (seg) {
     for (i=0; i<MRB_SEGMENT_SIZE; i++) {
       mrb_sym key = seg->key[i];
-      /* found room in last segment after last_len */
+      /* Found room in last segment after last_len */
       if (!seg->next && i >= t->last_len) {
         seg->key[i] = sym;
         seg->val[i] = val;
@@ -80,7 +98,7 @@ iv_put(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value val)
     seg = seg->next;
   }
 
-  /* not found */
+  /* Not found */
   t->size++;
   if (matched_seg) {
     matched_seg->key[matched_idx] = sym;
@@ -103,6 +121,18 @@ iv_put(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value val)
   return;
 }
 
+/*
+ * Get a value for a symbol from the instance the variable table.
+ *
+ * Parameters
+ *   mrb
+ *   t     the variable table to be searched.
+ *   sym   the symbol to be used as the key.
+ *   vp    the value pointer. Recieves the value if the specified symbol contains
+ *         in the instance variable table.
+ * Returns
+ *   true if the specfiyed symbol contains in the instance variable table.
+ */
 static mrb_bool
 iv_get(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value *vp)
 {
@@ -127,6 +157,17 @@ iv_get(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value *vp)
   return FALSE;
 }
 
+/*
+ * Deletes the value for the symbol from the instance variable table.
+ *
+ * Parameters
+ *   t    the variable table to be searched.
+ *   sym  the symbol to be used as the key.
+ *   vp   the value pointer. Recieve the deleted value if the symbol contans
+ *        in the instance varible table.
+ * Returns
+ *   true if the specfied symbol contains in the instance variable table.
+ */
 static mrb_bool
 iv_del(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value *vp)
 {
@@ -916,7 +957,7 @@ mrb_const_remove(mrb_state *mrb, mrb_value mod, mrb_sym sym)
 void
 mrb_define_const(mrb_state *mrb, struct RClass *mod, const char *name, mrb_value v)
 {
-  mrb_obj_iv_set(mrb, (struct RObject*)mod, mrb_intern(mrb, name), v);
+  mrb_obj_iv_set(mrb, (struct RObject*)mod, mrb_intern_cstr(mrb, name), v);
 }
 
 void
diff --git a/src/vm.c b/src/vm.c
index 38e3cd6ed..3cdf57551 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -1,4 +1,4 @@
-/*
+ /*
 ** vm.c - virtual machine for mruby
 **
 ** See Copyright Notice in mruby.h
@@ -92,12 +92,12 @@ stack_init(mrb_state *mrb)
 {
   struct mrb_context *c = mrb->c;
 
-  /* assert(mrb->stack == NULL); */
+  /* mrb_assert(mrb->stack == NULL); */
   c->stbase = (mrb_value *)mrb_calloc(mrb, STACK_INIT_SIZE, sizeof(mrb_value));
   c->stend = c->stbase + STACK_INIT_SIZE;
   c->stack = c->stbase;
 
-  /* assert(ci == NULL); */
+  /* mrb_assert(ci == NULL); */
   c->cibase = (mrb_callinfo *)mrb_calloc(mrb, CALLINFO_INIT_SIZE, sizeof(mrb_callinfo));
   c->ciend = c->cibase + CALLINFO_INIT_SIZE;
   c->ci = c->cibase;
@@ -174,22 +174,22 @@ uvenv(mrb_state *mrb, int up)
   struct REnv *e = mrb->c->ci->proc->env;
 
   while (up--) {
-    if (!e) return 0;
+    if (!e) return NULL;
     e = (struct REnv*)e->c;
   }
   return e;
 }
 
-static inline int
+static inline mrb_bool
 is_strict(mrb_state *mrb, struct REnv *e)
 {
   int cioff = e->cioff;
 
   if (cioff >= 0 && mrb->c->cibase[cioff].proc &&
       MRB_PROC_STRICT_P(mrb->c->cibase[cioff].proc)) {
-    return 1;
+    return TRUE;
   }
-  return 0;
+  return FALSE;
 }
 
 static inline struct REnv*
@@ -279,7 +279,7 @@ ecall(mrb_state *mrb, int i)
 mrb_value
 mrb_funcall(mrb_state *mrb, mrb_value self, const char *name, int argc, ...)
 {
-  mrb_sym mid = mrb_intern(mrb, name);
+  mrb_sym mid = mrb_intern_cstr(mrb, name);
 
   if (argc == 0) {
     return mrb_funcall_argv(mrb, self, mid, 0, 0);
@@ -544,7 +544,7 @@ void mrb_gv_val_set(mrb_state *mrb, mrb_sym sym, mrb_value val);
 mrb_value
 mrb_run(mrb_state *mrb, struct RProc *proc, mrb_value self)
 {
-  /* assert(mrb_proc_cfunc_p(proc)) */
+  /* mrb_assert(mrb_proc_cfunc_p(proc)) */
   mrb_irep *irep = proc->body.irep;
   mrb_code *pc = irep->iseq;
   mrb_value *pool = irep->pool;
@@ -1261,7 +1261,7 @@ mrb_run(mrb_state *mrb, struct RProc *proc, mrb_value self)
           mrb->c->stack = mrb->c->stbase + ci[1].stackidx;
           if (ci[1].acc < 0 && prev_jmp) {
             mrb->jmp = prev_jmp;
-            longjmp(*(jmp_buf*)mrb->jmp, 1);
+            mrb_longjmp(mrb);
           }
           while (eidx > ci->eidx) {
             ecall(mrb, --eidx);
@@ -2127,3 +2127,9 @@ mrb_run(mrb_state *mrb, struct RProc *proc, mrb_value self)
   }
   END_DISPATCH;
 }
+
+void
+mrb_longjmp(mrb_state *mrb)
+{
+  longjmp(*(jmp_buf*)mrb->jmp, 1);
+}
diff --git a/tasks/mrbgem_spec.rake b/tasks/mrbgem_spec.rake
index 3363b4885..df55e749f 100644
--- a/tasks/mrbgem_spec.rake
+++ b/tasks/mrbgem_spec.rake
@@ -275,13 +275,20 @@ module MRuby
             req_versions = dep[:requirements]
 
             # check each GEM dependency against all available GEMs
+            found_dep_gem = false
             each do |dep_g|
               if name == dep_g.name
                 unless dep_g.version_ok?(req_versions)
                   fail "#{name} version should be #{req_versions.join(' and ')} but was '#{dep_g.version}'"
                 end
+
+                found_dep_gem = true
+                break
               end
             end
+
+            fail "The GEM '#{g.name}' depends on the GEM '#{name}' but it could not be found" unless found_dep_gem
+
           end
         end
       end
diff --git a/tasks/mrbgems.rake b/tasks/mrbgems.rake
index 5f156c45a..d8f56f88e 100644
--- a/tasks/mrbgems.rake
+++ b/tasks/mrbgems.rake
@@ -74,9 +74,10 @@ please check the following additional licenses too:
 GEMS_LEGAL
 
         gems.map do |g|
+          authors = [g.authors].flatten.sort.join(", ")
           f.puts
           f.puts "GEM: #{g.name}"
-          f.puts "Copyright (c) #{Time.now.year} #{g.authors}"
+          f.puts "Copyright (c) #{Time.now.year} #{authors}"
           f.puts "License: #{g.licenses}"
         end
       end
diff --git a/tasks/mrbgems_test.rake b/tasks/mrbgems_test.rake
index 717f0d76b..1050b84bb 100644
--- a/tasks/mrbgems_test.rake
+++ b/tasks/mrbgems_test.rake
@@ -38,7 +38,7 @@ MRuby.each_target do
             f.puts %Q[  }]
             f.puts %Q[  mrb_const_set(mrb2, mrb_obj_value(mrb2->object_class), mrb_intern(mrb2, "GEMNAME"), mrb_str_new(mrb2, "#{g.name}", #{g.name.length}));]
 
-            if not g.test_args.empty?
+            unless g.test_args.empty?
               f.puts %Q[  test_args_hash = mrb_hash_new_capa(mrb, #{g.test_args.length}); ]
               g.test_args.each do |arg_name, arg_value|
                 escaped_arg_name = arg_name.gsub('\\', '\\\\\\\\').gsub('"', '\"')
diff --git a/tasks/mruby_build.rake b/tasks/mruby_build.rake
index eeebd161b..ef7f06a81 100644
--- a/tasks/mruby_build.rake
+++ b/tasks/mruby_build.rake
@@ -43,7 +43,7 @@ module MRuby
     end
     include Rake::DSL
     include LoadGems
-    attr_accessor :name, :bins, :exts, :file_separator
+    attr_accessor :name, :bins, :exts, :file_separator, :build_dir
     attr_reader :libmruby, :gems
 
     COMPILERS = %w(cc cxx objc asm)
@@ -63,6 +63,7 @@ module MRuby
         end
 
         @file_separator = '/'
+        @build_dir = "#{MRUBY_ROOT}/build/#{@name}"
         @cc = Command::Compiler.new(self, %w(.c))
         @cxx = Command::Compiler.new(self, %w(.cc .cxx .cpp))
         @objc = Command::Compiler.new(self, %w(.m))
@@ -95,10 +96,6 @@ module MRuby
       MRUBY_ROOT
     end
 
-    def build_dir
-      "#{MRUBY_ROOT}/build/#{self.name}"
-    end
-
     def mrbcfile
       MRuby.targets['host'].exefile("#{MRuby.targets['host'].build_dir}/bin/mrbc")
     end
diff --git a/tasks/mruby_build_commands.rake b/tasks/mruby_build_commands.rake
index 1d69fa54d..349b8717d 100644
--- a/tasks/mruby_build_commands.rake
+++ b/tasks/mruby_build_commands.rake
@@ -220,19 +220,28 @@ module MRuby
 
   class Command::Git < Command
     attr_accessor :flags
-    attr_accessor :clone_options
+    attr_accessor :clone_options, :pull_options
 
     def initialize(build)
       super
       @command = 'git'
       @flags = []
       @clone_options = "clone %{flags} %{url} %{dir}"
+      @pull_options = "pull"
     end
 
     def run_clone(dir, url, _flags = [])
       _pp "GIT", url, dir.relative_path
       _run clone_options, { :flags => [flags, _flags].flatten.join(' '), :url => url, :dir => filename(dir) }
     end
+
+    def run_pull(dir, url)
+      root = Dir.pwd
+      Dir.chdir dir
+      _pp "GIT PULL", url, dir.relative_path
+      _run pull_options
+      Dir.chdir root
+    end
   end
 
   class Command::Mrbc < Command
@@ -250,9 +259,14 @@ module MRuby
       infiles.each do |f|
         _pp "MRBC", f.relative_path, nil, :indent => 2
       end
-      IO.popen("#{filename @command} #{@compile_options % {:funcname => funcname}} #{infiles.join(' ')}", 'r+') do |io|
+      IO.popen("#{filename @command} #{@compile_options % {:funcname => funcname}} #{filename(infiles).join(' ')}", 'r+') do |io|
         out.puts io.read
       end
+      # if mrbc execution fail, drop the file
+      unless $?.exitstatus
+        File.delete(out.path)
+        exit -1
+      end
     end
   end
 
diff --git a/tasks/mruby_build_gem.rake b/tasks/mruby_build_gem.rake
index 870ccfa57..24aea71ab 100644
--- a/tasks/mruby_build_gem.rake
+++ b/tasks/mruby_build_gem.rake
@@ -39,14 +39,20 @@ module MRuby
         gemdir = "#{root}/mrbgems/#{params[:core]}"
       elsif params[:git]
         url = params[:git]
-        gemdir = "build/mrbgems/#{url.match(/([-\w]+)(\.[-\w]+|)$/).to_a[1]}"
-        return gemdir if File.exists?(gemdir)
+        gemdir = "#{build_dir}/mrbgems/#{url.match(/([-\w]+)(\.[-\w]+|)$/).to_a[1]}"
 
-        options = [params[:options]] || []
-        options << "--branch \"#{params[:branch]}\"" if params[:branch]
-
-        FileUtils.mkdir_p "build/mrbgems"
-        git.run_clone gemdir, url, options
+        if File.exists?(gemdir)
+          if $pull_gems
+            git.run_pull gemdir, url
+          else
+            gemdir
+          end
+        else
+          options = [params[:options]] || []
+          options << "--branch \"#{params[:branch]}\"" if params[:branch]
+          FileUtils.mkdir_p "#{build_dir}/mrbgems"
+          git.run_clone gemdir, url, options
+        end
       else
         fail "unknown gem option #{params}"
       end
diff --git a/tasks/toolchains/androideabi.rake b/tasks/toolchains/androideabi.rake
index a69fd1a9d..a20027c0d 100644
--- a/tasks/toolchains/androideabi.rake
+++ b/tasks/toolchains/androideabi.rake
@@ -41,20 +41,23 @@ MRuby::Toolchain.new(:androideabi) do |conf|
   end
 
   if ANDROID_STANDALONE_TOOLCHAIN == nil then
-    if RUBY_PLATFORM.include?('darwin') then
+    case RUBY_PLATFORM
+    when /cygwin|mswin|mingw|bccwin|wince|emx/i
+      HOST_PLATFORM = 'windows'
+    when /darwin/i
       HOST_PLATFORM = 'darwin-x86'
-    elsif RUBY_PLATFORM.include?('linux') then
+    when /x86_64-linux/i
+      HOST_PLATFORM = 'linux-x86_64'
+    when /linux/i
       HOST_PLATFORM = 'linux-x86'
-    elsif RUBY_PLATFORM.include?('win') then
-      HOST_PLATFORM = 'windows'
     else
-      # Unknown host platform.
+      # Unknown host platform
     end
 
     ANDROID_TARGET_PLATFORM = ENV['ANDROID_TARGET_PLATFORM'] || DEFAULT_ANDROID_TARGET_PLATFORM
 
     path_to_toolchain = ANDROID_NDK_HOME + '/toolchains/'
-	path_to_sysroot   = ANDROID_NDK_HOME + '/platforms/' + ANDROID_TARGET_PLATFORM
+    path_to_sysroot   = ANDROID_NDK_HOME + '/platforms/' + ANDROID_TARGET_PLATFORM
     if ANDROID_TOOLCHAIN.downcase == 'gcc' then
       case ANDROID_TARGET_ARCH.downcase
       when 'arch-arm',  'arm'  then
diff --git a/test/t/integer.rb b/test/t/integer.rb
index 46011f94a..9b19216d9 100644
--- a/test/t/integer.rb
+++ b/test/t/integer.rb
@@ -104,6 +104,14 @@ assert('Integer#<<', '15.2.8.3.12') do
   #   00010111 (23)
   # = 00101110 (46)
   assert_equal 23 << 1, 46
+
+  # Left Shift by a negative is Right Shift
+  assert_equal 46 << -1, 23
+
+  # Raise when shift is too large
+  assert_raise(RangeError) do
+    2 << 128
+  end
 end
 
 assert('Integer#>>', '15.2.8.3.13') do
@@ -111,6 +119,17 @@ assert('Integer#>>', '15.2.8.3.13') do
   #   00101110 (46)
   # = 00010111 (23)
   assert_equal 46 >> 1, 23
+
+  # Right Shift by a negative is Left Shift
+  assert_equal 23 >> -1, 46
+
+  # Don't raise on large Right Shift
+  assert_equal 23 >> 128, 0
+
+  # Raise when shift is too large
+  assert_raise(RangeError) do
+    2 >> -128
+  end
 end
 
 assert('Integer#ceil', '15.2.8.3.14') do
diff --git a/test/t/module.rb b/test/t/module.rb
index 9d735f5da..618b57f06 100644
--- a/test/t/module.rb
+++ b/test/t/module.rb
@@ -37,6 +37,145 @@ assert('Module#append_features', '15.2.2.4.10') do
   assert_equal Test4AppendFeatures2.const_get(:Const4AppendFeatures2), Test4AppendFeatures2
 end
 
+assert('Module#attr NameError') do
+  %w[
+    foo?
+    @foo
+    @@foo
+    $foo
+  ].each do |name|
+    module NameTest; end
+
+    assert_raise(NameError) do
+      NameTest.module_eval { attr_reader name.to_sym }
+    end
+
+    assert_raise(NameError) do
+      NameTest.module_eval { attr_writer name.to_sym }
+    end
+
+    assert_raise(NameError) do
+      NameTest.module_eval { attr name.to_sym }
+    end
+
+    assert_raise(NameError) do
+      NameTest.module_eval { attr_accessor name.to_sym }
+    end
+  end
+
+end
+
+assert('Module#attr', '15.2.2.4.11') do
+  class AttrTest
+    class << self
+      attr :cattr
+      def cattr_val=(val)
+        @cattr = val
+      end
+    end
+    attr :iattr
+    def iattr_val=(val)
+      @iattr = val
+    end
+  end
+
+  test = AttrTest.new
+  assert_true AttrTest.respond_to?(:cattr)
+  assert_true test.respond_to?(:iattr)
+
+  assert_false AttrTest.respond_to?(:vattr=)
+  assert_false test.respond_to?(:iattr=)
+
+  test.iattr_val = 'test'
+  assert_equal 'test', test.iattr
+
+  AttrTest.cattr_val = 'test'
+  assert_equal 'test', AttrTest.cattr
+end
+
+assert('Module#attr_accessor', '15.2.2.4.12') do
+  class AttrTestAccessor
+    class << self
+      attr_accessor :cattr
+    end
+    attr_accessor :iattr, 'iattr2'
+  end
+
+  attr_instance = AttrTestAccessor.new
+  assert_true AttrTestAccessor.respond_to?(:cattr=)
+  assert_true attr_instance.respond_to?(:iattr=)
+  assert_true attr_instance.respond_to?(:iattr2=)
+  assert_true AttrTestAccessor.respond_to?(:cattr)
+  assert_true attr_instance.respond_to?(:iattr)
+  assert_true attr_instance.respond_to?(:iattr2)
+
+  attr_instance.iattr = 'test'
+  assert_equal 'test', attr_instance.iattr
+
+  AttrTestAccessor.cattr = 'test'
+  assert_equal 'test', AttrTestAccessor.cattr
+end
+
+assert('Module#attr_reader', '15.2.2.4.13') do
+  class AttrTestReader
+    class << self
+      attr_reader :cattr
+      def cattr_val=(val)
+        @cattr = val
+      end
+    end
+    attr_reader :iattr, 'iattr2'
+    def iattr_val=(val)
+      @iattr = val
+    end
+  end
+
+  attr_instance = AttrTestReader.new
+  assert_true AttrTestReader.respond_to?(:cattr)
+  assert_true attr_instance.respond_to?(:iattr)
+  assert_true attr_instance.respond_to?(:iattr2)
+
+  assert_false AttrTestReader.respond_to?(:cattr=)
+  assert_false attr_instance.respond_to?(:iattr=)
+  assert_false attr_instance.respond_to?(:iattr2=)
+
+  attr_instance.iattr_val = 'test'
+  assert_equal 'test', attr_instance.iattr
+
+  AttrTestReader.cattr_val = 'test'
+  assert_equal 'test', AttrTestReader.cattr
+end
+
+assert('Module#attr_writer', '15.2.2.4.14') do
+  class AttrTestWriter
+    class << self
+      attr_writer :cattr
+      def cattr_val
+        @cattr
+      end
+    end
+    attr_writer :iattr, 'iattr2'
+    def iattr_val
+      @iattr
+    end
+  end
+
+  attr_instance = AttrTestWriter.new
+  assert_true AttrTestWriter.respond_to?(:cattr=)
+  assert_true attr_instance.respond_to?(:iattr=)
+  assert_true attr_instance.respond_to?(:iattr2=)
+
+  assert_false AttrTestWriter.respond_to?(:cattr)
+  assert_false attr_instance.respond_to?(:iattr)
+  assert_false attr_instance.respond_to?(:iattr2)
+
+  attr_instance.iattr = 'test'
+  assert_equal 'test', attr_instance.iattr_val
+
+  AttrTestWriter.cattr = 'test'
+  assert_equal 'test', AttrTestWriter.cattr_val
+end
+
 assert('Module#class_eval', '15.2.2.4.15') do
   class Test4ClassEval
     @a = 11
diff --git a/test/t/nil.rb b/test/t/nil.rb
index 99b1215e9..08d2acdf1 100644
--- a/test/t/nil.rb
+++ b/test/t/nil.rb
@@ -27,4 +27,3 @@ end
 assert('NilClass#to_s', '15.2.4.3.5') do
   assert_equal nil.to_s, ''
 end
-
diff --git a/test/t/range.rb b/test/t/range.rb
index fdf6b415c..da25abc0e 100644
--- a/test/t/range.rb
+++ b/test/t/range.rb
@@ -12,6 +12,7 @@ end
 assert('Range#==', '15.2.14.4.1') do
   assert_true (1..10) == (1..10)
   assert_false (1..10) == (1..100)
+  assert_true (1..10) == Range.new(1.0, 10.0)
 end
 
 assert('Range#===', '15.2.14.4.2') do
@@ -72,3 +73,10 @@ assert('Range#member?', '15.2.14.4.11') do
   assert_true a.member?(5)
   assert_false a.member?(20)
 end
+
+assert('Range#eql?', '15.2.14.4.14') do
+  assert_true (1..10).eql? (1..10)
+  assert_false (1..10).eql? (1..100)
+  assert_false (1..10).eql? (Range.new(1.0, 10.0))
+  assert_false (1..10).eql? "1..10"
+end
diff --git a/test/t/string.rb b/test/t/string.rb
index ddae92d4a..c208835b4 100644
--- a/test/t/string.rb
+++ b/test/t/string.rb
@@ -399,12 +399,12 @@ end
 
 assert('String#to_i', '15.2.10.5.38') do
   a = ''.to_i
-  b = '123456789'.to_i
+  b = '32143'.to_i
   c = 'a'.to_i(16)
   d = '100'.to_i(2)
 
   assert_equal a, 0
-  assert_equal b, 123456789
+  assert_equal b, 32143
   assert_equal c, 10
   assert_equal d, 4
 end
diff --git a/travis_config.rb b/travis_config.rb
index 040b1a255..bd2939f94 100644
--- a/travis_config.rb
+++ b/travis_config.rb
@@ -3,4 +3,5 @@ MRuby::Build.new do |conf|
 
   # include all core GEMs
   conf.gembox 'full-core'
+  conf.cc.defines = %w(MRB_DEBUG)
 end