23 files changed, 369 insertions, 180 deletions
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 000000000..3c1a7e07e
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,24 @@
+name: CIFuzz
+on: [pull_request]
+jobs:
+  Fuzzing:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Build Fuzzers
+      uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
+      with:
+        oss-fuzz-project-name: 'mruby'
+        dry-run: false
+    - name: Run Fuzzers
+      uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
+      with:
+        oss-fuzz-project-name: 'mruby'
+        fuzz-seconds: 600
+        dry-run: false
+    - name: Upload Crash
+      uses: actions/upload-artifact@v1
+      if: failure()
+      with:
+        name: artifacts
+        path: ./out/artifacts
+
diff --git a/README.md b/README.md
index ab518734b..b11e9412d 100644
--- a/README.md
+++ b/README.md
@@ -34,7 +34,7 @@ The URL of the mruby home-page is: https://mruby.org.
 
 ## Mailing list
 
-We don't have a mailing list, but you can use [GitHub issues](https://github.com/mruby/mruby).
+We don't have a mailing list, but you can use [GitHub issues](https://github.com/mruby/mruby/issues).
 
 ## How to compile and install (mruby and gems)
 
diff --git a/appveyor.yml b/appveyor.yml
index a91834cef..bf4fb3f17 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -14,10 +14,18 @@ environment:
     # Visual Studio 2017 64bit
     - visualcpp: C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars64.bat
 
+    # Visual Studio 2017 32bit
+    - visualcpp: C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvarsall.bat
+      machine: x86
+
     # Visual Studio 2015 64bit
     - visualcpp: C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat
       machine: amd64
 
+    # Visual Studio 2015 32bit
+    - visualcpp: C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat
+      machine: x86
+
     # Visual Studio 2013 64bit
     - visualcpp: C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat
       machine: amd64
diff --git a/examples/targets/build_config_dreamcast_shelf.rb b/examples/targets/build_config_dreamcast_shelf.rb
new file mode 100644
index 000000000..fd6915acb
--- /dev/null
+++ b/examples/targets/build_config_dreamcast_shelf.rb
@@ -0,0 +1,108 @@
+MRuby::Build.new do |conf|
+  # Gets set by the VS command prompts
+  if ENV['VisualStudioVersion'] || ENV['VSINSTALLDIR']
+    toolchain :visualcpp
+  else
+    toolchain :gcc
+  end
+
+  enable_debug
+
+  # Include the default GEMs
+  conf.gembox 'default'
+end
+
+# Cross Compiling configuration for the Sega Dreamcast
+# This configuration requires KallistiOS (KOS)
+# https://dreamcast.wiki
+#
+# Tested on GNU/Linux, MinGW-w64/MSYS2, Cygwin, macOS and MinGW/MSYS (see below)
+#
+MRuby::CrossBuild.new("dreamcast") do |conf|
+  toolchain :gcc
+
+  # Support for DreamSDK (based on MinGW/MSYS)
+  # To compile mruby with DreamSDK, RubyInstaller for Windows should be installed
+  DREAMSDK_HOME = ENV["DREAMSDK_HOME"]
+  MSYS_ROOT = !(DREAMSDK_HOME.nil? || DREAMSDK_HOME.empty?) ? "#{DREAMSDK_HOME}/msys/1.0" : ""
+ 
+  # Setting paths
+  DREAMCAST_PATH = "#{MSYS_ROOT}/opt/toolchains/dc"
+  KOS_PATH = "#{DREAMCAST_PATH}/kos"
+  BIN_PATH = "#{DREAMCAST_PATH}/sh-elf/bin"
+
+  # C compiler
+  # Flags were extracted from KallistiOS environment files
+  conf.cc do |cc|
+    cc.command = "#{BIN_PATH}/sh-elf-gcc"	
+    cc.include_paths << ["#{KOS_PATH}/include", "#{KOS_PATH}/kernel/arch/dreamcast/include", "#{KOS_PATH}/addons/include", "#{KOS_PATH}/../kos-ports/include"]
+    cc.flags << ["-O2", "-fomit-frame-pointer", "-ml", "-m4-single-only", "-ffunction-sections", "-fdata-sections", "-Wall", "-g", "-fno-builtin", "-ml", "-m4-single-only", "-Wl,-Ttext=0x8c010000", "-Wl,--gc-sections", "-T#{KOS_PATH}/utils/ldscripts/shlelf.xc", "-nodefaultlibs"]
+    cc.compile_options = "%{flags} -o %{outfile} -c %{infile}"
+    cc.defines << %w(_arch_dreamcast)
+    cc.defines << %w(_arch_sub_pristine)
+  end
+
+  # C++ compiler
+  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.flags << %w(-fno-rtti -fno-exceptions)
+    cxx.defines = conf.cc.defines.dup
+    cxx.compile_options = conf.cc.compile_options.dup
+  end
+ 
+  # Linker
+  # There is an issue when making the mruby library with KallistiOS:
+  # 'newlib_kill.o' and 'newlib_getpid.o' aren't found so they are explicitly 
+  # specified here at least for now.
+  conf.linker do |linker|
+    linker.command="#{BIN_PATH}/sh-elf-gcc"
+    linker.flags << ["#{MSYS_ROOT}/opt/toolchains/dc/kos/kernel/build/newlib_kill.o", "#{MSYS_ROOT}/opt/toolchains/dc/kos/kernel/build/newlib_getpid.o", "-Wl,--start-group -lkallisti -lc -lgcc -Wl,--end-group"]
+    linker.library_paths << ["#{KOS_PATH}/lib/dreamcast", "#{KOS_PATH}/addons/lib/dreamcast", "#{KOS_PATH}/../kos-ports/lib"]
+  end  
+
+  # Archiver
+  conf.archiver do |archiver|
+    archiver.command = "#{BIN_PATH}/sh-elf-ar"
+    archiver.archive_options = 'rcs %{outfile} %{objs}'
+  end
+
+  # No executables
+  conf.bins = []
+
+  # Do not build executable test
+  conf.build_mrbtest_lib_only
+
+  # Disable C++ exception
+  conf.disable_cxx_exception
+  
+  # Gems from core
+  # removing mruby-io
+  conf.gem :core => "mruby-metaprog"
+  conf.gem :core => "mruby-pack"
+  conf.gem :core => "mruby-sprintf"
+  conf.gem :core => "mruby-print"
+  conf.gem :core => "mruby-math"
+  conf.gem :core => "mruby-time"
+  conf.gem :core => "mruby-struct"
+  conf.gem :core => "mruby-compar-ext"
+  conf.gem :core => "mruby-enum-ext"
+  conf.gem :core => "mruby-string-ext"
+  conf.gem :core => "mruby-numeric-ext"
+  conf.gem :core => "mruby-array-ext"
+  conf.gem :core => "mruby-hash-ext"
+  conf.gem :core => "mruby-range-ext"
+  conf.gem :core => "mruby-proc-ext"
+  conf.gem :core => "mruby-symbol-ext"
+  conf.gem :core => "mruby-random"
+  conf.gem :core => "mruby-object-ext"
+  conf.gem :core => "mruby-objectspace"
+  conf.gem :core => "mruby-fiber"
+  conf.gem :core => "mruby-enumerator"
+  conf.gem :core => "mruby-enum-lazy"
+  conf.gem :core => "mruby-toplevel-ext"
+  conf.gem :core => "mruby-kernel-ext"
+  conf.gem :core => "mruby-class-ext"
+  conf.gem :core => "mruby-compiler"
+end
diff --git a/include/mrbconf.h b/include/mrbconf.h
index 3a574c7d2..35762a8f0 100644
--- a/include/mrbconf.h
+++ b/include/mrbconf.h
@@ -38,7 +38,12 @@
 
 /* add -DMRB_METHOD_T_STRUCT on machines that use higher bits of pointers */
 /* no MRB_METHOD_T_STRUCT requires highest 2 bits of function pointers to be zero */
-//#define MRB_METHOD_T_STRUCT
+#ifndef MRB_METHOD_T_STRUCT
+  // can't use highest 2 bits of function pointers on 32bit Windows.
+# if defined(_WIN32) && !defined(_WIN64)
+#   define MRB_METHOD_T_STRUCT
+# endif
+#endif
 
 /* add -DMRB_INT32 to use 32bit integer for mrb_int; conflict with MRB_INT64;
    Default for 32-bit CPU mode. */
diff --git a/include/mruby.h b/include/mruby.h
index 671053ff9..7419618fd 100644
--- a/include/mruby.h
+++ b/include/mruby.h
@@ -70,6 +70,11 @@
 
 #include "mrbconf.h"
 
+#include <mruby/common.h>
+#include <mruby/value.h>
+#include <mruby/gc.h>
+#include <mruby/version.h>
+
 #ifndef MRB_WITHOUT_FLOAT
 #ifndef FLT_EPSILON
 #define FLT_EPSILON (1.19209290e-07f)
@@ -88,11 +93,6 @@
 #endif
 #endif
 
-#include <mruby/common.h>
-#include <mruby/value.h>
-#include <mruby/gc.h>
-#include <mruby/version.h>
-
 /**
  * MRuby C API entry point
  */
diff --git a/include/mruby/common.h b/include/mruby/common.h
index 5be9a40c6..f704ef8df 100644
--- a/include/mruby/common.h
+++ b/include/mruby/common.h
@@ -74,6 +74,16 @@ MRB_BEGIN_DECL
 #endif
 #endif
 
+/** Declare mingw versions */
+#if defined(__MINGW32__) || defined(__MINGW64__)
+# include <_mingw.h>
+# if defined(__MINGW64_VERSION_MAJOR)
+#  define MRB_MINGW64_VERSION  (__MINGW64_VERSION_MAJOR * 1000 + __MINGW64_VERSION_MINOR)
+# elif defined(__MINGW32_MAJOR_VERSION)
+#  define MRB_MINGW32_VERSION  (__MINGW32_MAJOR_VERSION * 1000 + __MINGW32_MINOR_VERSION)
+# endif
+#endif
+
 MRB_END_DECL
 
 #endif  /* MRUBY_COMMON_H */
diff --git a/mrbgems/mruby-array-ext/mrblib/array.rb b/mrbgems/mruby-array-ext/mrblib/array.rb
index 5492ba2eb..f3246af4f 100644
--- a/mrbgems/mruby-array-ext/mrblib/array.rb
+++ b/mrbgems/mruby-array-ext/mrblib/array.rb
@@ -688,37 +688,6 @@ class Array
 
   ##
   #  call-seq:
-  #     ary.delete_if { |item| block }  -> ary
-  #     ary.delete_if                   -> Enumerator
-  #
-  #  Deletes every element of +self+ for which block evaluates to +true+.
-  #
-  #  The array is changed instantly every time the block is called, not after
-  #  the iteration is over.
-  #
-  #  See also Array#reject!
-  #
-  #  If no block is given, an Enumerator is returned instead.
-  #
-  #     scores = [ 97, 42, 75 ]
-  #     scores.delete_if {|score| score < 80 }   #=> [97]
-
-  def delete_if(&block)
-    return to_enum :delete_if unless block
-
-    idx = 0
-    while idx < self.size do
-      if block.call(self[idx])
-        self.delete_at(idx)
-      else
-        idx += 1
-      end
-    end
-    self
-  end
-
-  ##
-  #  call-seq:
   #     ary.keep_if { |item| block } -> ary
   #     ary.keep_if                  -> Enumerator
   #
diff --git a/mrbgems/mruby-array-ext/test/array.rb b/mrbgems/mruby-array-ext/test/array.rb
index 51172f9a8..2955ef391 100644
--- a/mrbgems/mruby-array-ext/test/array.rb
+++ b/mrbgems/mruby-array-ext/test/array.rb
@@ -299,19 +299,6 @@ end
 #assert("Array#bsearch_index") do
 #end
 
-assert("Array#delete_if") do
-  a = [1, 2, 3, 4, 5]
-  assert_equal [1, 2, 3, 4, 5], a.delete_if { false }
-  assert_equal [1, 2, 3, 4, 5], a
-
-  a = [1, 2, 3, 4, 5]
-  assert_equal [], a.delete_if { true }
-  assert_equal [], a
-
-  a = [ 1, 2, 3, 4, 5 ]
-  assert_equal [1, 2, 3], a.delete_if { |val| val > 3 }
-end
-
 assert("Array#keep_if") do
   a = [1, 2, 3, 4, 5]
   assert_equal [1, 2, 3, 4, 5], a.keep_if { true }
diff --git a/mrbgems/mruby-error/src/exception.c b/mrbgems/mruby-error/src/exception.c
index ec4870dc0..e0ea28ac8 100644
--- a/mrbgems/mruby-error/src/exception.c
+++ b/mrbgems/mruby-error/src/exception.c
@@ -8,7 +8,7 @@ mrb_protect(mrb_state *mrb, mrb_func_t body, mrb_value data, mrb_bool *state)
   struct mrb_jmpbuf *prev_jmp = mrb->jmp;
   struct mrb_jmpbuf c_jmp;
   mrb_value result = mrb_nil_value();
-  mrb_int ai = mrb_gc_arena_save(mrb);
+  int ai = mrb_gc_arena_save(mrb);
 
   if (state) { *state = FALSE; }
 
@@ -34,7 +34,7 @@ mrb_ensure(mrb_state *mrb, mrb_func_t body, mrb_value b_data, mrb_func_t ensure,
   struct mrb_jmpbuf *prev_jmp = mrb->jmp;
   struct mrb_jmpbuf c_jmp;
   mrb_value result;
-  mrb_int ai = mrb_gc_arena_save(mrb);
+  int ai = mrb_gc_arena_save(mrb);
 
   MRB_TRY(&c_jmp) {
     mrb->jmp = &c_jmp;
@@ -71,7 +71,7 @@ mrb_rescue_exceptions(mrb_state *mrb, mrb_func_t body, mrb_value b_data, mrb_fun
   mrb_value result;
   mrb_bool error_matched = FALSE;
   mrb_int i;
-  mrb_int ai = mrb_gc_arena_save(mrb);
+  int ai = mrb_gc_arena_save(mrb);
 
   MRB_TRY(&c_jmp) {
     mrb->jmp = &c_jmp;
diff --git a/mrbgems/mruby-io/include/mruby/ext/io.h b/mrbgems/mruby-io/include/mruby/ext/io.h
index 5d1dde354..4bcbbe914 100644
--- a/mrbgems/mruby-io/include/mruby/ext/io.h
+++ b/mrbgems/mruby-io/include/mruby/ext/io.h
@@ -19,13 +19,31 @@ struct mrb_io {
                is_socket:1;
 };
 
-#define FMODE_READABLE             0x00000001
-#define FMODE_WRITABLE             0x00000002
-#define FMODE_READWRITE            (FMODE_READABLE|FMODE_WRITABLE)
-#define FMODE_BINMODE              0x00000004
-#define FMODE_APPEND               0x00000040
-#define FMODE_CREATE               0x00000080
-#define FMODE_TRUNC                0x00000800
+#define MRB_O_RDONLY            0x0000
+#define MRB_O_WRONLY            0x0001
+#define MRB_O_RDWR              0x0002
+#define MRB_O_ACCMODE           (MRB_O_RDONLY | MRB_O_WRONLY | MRB_O_RDWR)
+#define MRB_O_NONBLOCK          0x0004
+#define MRB_O_APPEND            0x0008
+#define MRB_O_SYNC              0x0010
+#define MRB_O_NOFOLLOW          0x0020
+#define MRB_O_CREAT             0x0040
+#define MRB_O_TRUNC             0x0080
+#define MRB_O_EXCL              0x0100
+#define MRB_O_NOCTTY            0x0200
+#define MRB_O_DIRECT            0x0400
+#define MRB_O_BINARY            0x0800
+#define MRB_O_SHARE_DELETE      0x1000
+#define MRB_O_TMPFILE           0x2000
+#define MRB_O_NOATIME           0x4000
+#define MRB_O_DSYNC             0x00008000 /* Ignored with MRB_INT16 and MRB_WITHOUT_FLOAT */
+#define MRB_O_RSYNC             0x00010000 /* Ignored with MRB_INT16 and MRB_WITHOUT_FLOAT */
+
+#define MRB_O_RDONLY_P(f)       ((mrb_bool)(((f) & MRB_O_ACCMODE) == MRB_O_RDONLY))
+#define MRB_O_WRONLY_P(f)       ((mrb_bool)(((f) & MRB_O_ACCMODE) == MRB_O_WRONLY))
+#define MRB_O_RDWR_P(f)         ((mrb_bool)(((f) & MRB_O_ACCMODE) == MRB_O_RDWR))
+#define MRB_O_READABLE_P(f)     ((mrb_bool)((((f) & MRB_O_ACCMODE) | 2) == 2))
+#define MRB_O_WRITABLE_P(f)     ((mrb_bool)(((((f) & MRB_O_ACCMODE) + 1) & 2) == 2))
 
 #define E_IO_ERROR                 (mrb_class_get(mrb, "IOError"))
 #define E_EOF_ERROR                (mrb_class_get(mrb, "EOFError"))
diff --git a/mrbgems/mruby-io/mrblib/file_constants.rb b/mrbgems/mruby-io/mrblib/file_constants.rb
index a68ee2598..bd77d53fe 100644
--- a/mrbgems/mruby-io/mrblib/file_constants.rb
+++ b/mrbgems/mruby-io/mrblib/file_constants.rb
@@ -1,21 +1,5 @@
 class File
   module Constants
-    RDONLY   = 0
-    WRONLY   = 1
-    RDWR     = 2
-    NONBLOCK = 4
-    APPEND   = 8
-
-    BINARY   = 0
-    SYNC     = 128
-    NOFOLLOW = 256
-    CREAT    = 512
-    TRUNC    = 1024
-    EXCL     = 2048
-
-    NOCTTY   = 131072
-    DSYNC    = 4194304
-
     FNM_SYSCASE  = 0
     FNM_NOESCAPE = 1
     FNM_PATHNAME = 2
diff --git a/mrbgems/mruby-io/src/file.c b/mrbgems/mruby-io/src/file.c
index ba1d770e3..dafcac533 100644
--- a/mrbgems/mruby-io/src/file.c
+++ b/mrbgems/mruby-io/src/file.c
@@ -407,11 +407,11 @@ mrb_file_size(mrb_state *mrb, mrb_value self)
 #ifdef MRB_WITHOUT_FLOAT
     mrb_raise(mrb, E_RUNTIME_ERROR, "File#size too large for MRB_WITHOUT_FLOAT");
 #else
-    return mrb_float_value(mrb, st.st_size);
+    return mrb_float_value(mrb, (mrb_float)st.st_size);
 #endif
   }
 
-  return mrb_fixnum_value(st.st_size);
+  return mrb_fixnum_value((mrb_int)st.st_size);
 }
 
 static int
@@ -604,4 +604,22 @@ mrb_init_file(mrb_state *mrb)
 #endif
   mrb_define_const(mrb, cnst, "NULL", mrb_str_new_cstr(mrb, NULL_FILE));
 
+  mrb_define_const(mrb, cnst, "RDONLY", mrb_fixnum_value(MRB_O_RDONLY));
+  mrb_define_const(mrb, cnst, "WRONLY", mrb_fixnum_value(MRB_O_WRONLY));
+  mrb_define_const(mrb, cnst, "RDWR", mrb_fixnum_value(MRB_O_RDWR));
+  mrb_define_const(mrb, cnst, "APPEND", mrb_fixnum_value(MRB_O_APPEND));
+  mrb_define_const(mrb, cnst, "CREAT", mrb_fixnum_value(MRB_O_CREAT));
+  mrb_define_const(mrb, cnst, "EXCL", mrb_fixnum_value(MRB_O_EXCL));
+  mrb_define_const(mrb, cnst, "TRUNC", mrb_fixnum_value(MRB_O_TRUNC));
+  mrb_define_const(mrb, cnst, "NONBLOCK", mrb_fixnum_value(MRB_O_NONBLOCK));
+  mrb_define_const(mrb, cnst, "NOCTTY", mrb_fixnum_value(MRB_O_NOCTTY));
+  mrb_define_const(mrb, cnst, "BINARY", mrb_fixnum_value(MRB_O_BINARY));
+  mrb_define_const(mrb, cnst, "SHARE_DELETE", mrb_fixnum_value(MRB_O_SHARE_DELETE));
+  mrb_define_const(mrb, cnst, "SYNC", mrb_fixnum_value(MRB_O_SYNC));
+  mrb_define_const(mrb, cnst, "DSYNC", mrb_fixnum_value(MRB_O_DSYNC));
+  mrb_define_const(mrb, cnst, "RSYNC", mrb_fixnum_value(MRB_O_RSYNC));
+  mrb_define_const(mrb, cnst, "NOFOLLOW", mrb_fixnum_value(MRB_O_NOFOLLOW));
+  mrb_define_const(mrb, cnst, "NOATIME", mrb_fixnum_value(MRB_O_NOATIME));
+  mrb_define_const(mrb, cnst, "DIRECT", mrb_fixnum_value(MRB_O_DIRECT));
+  mrb_define_const(mrb, cnst, "TMPFILE", mrb_fixnum_value(MRB_O_TMPFILE));
 }
diff --git a/mrbgems/mruby-io/src/io.c b/mrbgems/mruby-io/src/io.c
index a5fe22e46..e28946597 100644
--- a/mrbgems/mruby-io/src/io.c
+++ b/mrbgems/mruby-io/src/io.c
@@ -32,8 +32,13 @@
   typedef long fsuseconds_t;
   typedef int fmode_t;
 
+  #ifndef O_TMPFILE
+    #define O_TMPFILE O_TEMPORARY
+  #endif
+
 #else
   #include <sys/wait.h>
+  #include <sys/time.h>
   #include <unistd.h>
   typedef size_t fsize_t;
   typedef time_t ftime_t;
@@ -51,6 +56,12 @@ typedef mrb_int pid_t;
 #include <stdio.h>
 #include <string.h>
 
+#define OPEN_ACCESS_MODE_FLAGS (O_RDONLY | O_WRONLY | O_RDWR)
+#define OPEN_RDONLY_P(f)       ((mrb_bool)(((f) & OPEN_ACCESS_MODE_FLAGS) == O_RDONLY))
+#define OPEN_WRONLY_P(f)       ((mrb_bool)(((f) & OPEN_ACCESS_MODE_FLAGS) == O_WRONLY))
+#define OPEN_RDWR_P(f)         ((mrb_bool)(((f) & OPEN_ACCESS_MODE_FLAGS) == O_RDWR))
+#define OPEN_READABLE_P(f)     ((mrb_bool)(OPEN_RDONLY_P(f) || OPEN_RDWR_P(f)))
+#define OPEN_WRITABLE_P(f)     ((mrb_bool)(OPEN_WRONLY_P(f) || OPEN_RDWR_P(f)))
 
 static void mrb_io_free(mrb_state *mrb, void *ptr);
 struct mrb_data_type mrb_io_type = { "IO", mrb_io_free };
@@ -58,7 +69,7 @@ struct mrb_data_type mrb_io_type = { "IO", mrb_io_free };
 
 static struct mrb_io *io_get_open_fptr(mrb_state *mrb, mrb_value self);
 static int mrb_io_modestr_to_flags(mrb_state *mrb, const char *modestr);
-static int mrb_io_flags_to_modenum(mrb_state *mrb, int flags);
+static int mrb_io_mode_to_flags(mrb_state *mrb, mrb_value mode);
 static void fptr_finalize(mrb_state *mrb, struct mrb_io *fptr, int quiet);
 
 static struct mrb_io *
@@ -100,30 +111,33 @@ io_set_process_status(mrb_state *mrb, pid_t pid, int status)
 static int
 mrb_io_modestr_to_flags(mrb_state *mrb, const char *mode)
 {
-  int flags = 0;
+  int flags;
   const char *m = mode;
 
   switch (*m++) {
     case 'r':
-      flags |= FMODE_READABLE;
+      flags = O_RDONLY;
       break;
     case 'w':
-      flags |= FMODE_WRITABLE | FMODE_CREATE | FMODE_TRUNC;
+      flags = O_WRONLY | O_CREAT | O_TRUNC;
       break;
     case 'a':
-      flags |= FMODE_WRITABLE | FMODE_APPEND | FMODE_CREATE;
+      flags = O_WRONLY | O_CREAT | O_APPEND;
       break;
     default:
       mrb_raisef(mrb, E_ARGUMENT_ERROR, "illegal access mode %s", mode);
+      flags = 0; /* not reached */
   }
 
   while (*m) {
     switch (*m++) {
       case 'b':
-        flags |= FMODE_BINMODE;
+#ifdef O_BINARY
+        flags |= O_BINARY;
+#endif
         break;
       case '+':
-        flags |= FMODE_READWRITE;
+        flags = (flags & ~OPEN_ACCESS_MODE_FLAGS) | O_RDWR;
         break;
       case ':':
         /* XXX: PASSTHROUGH*/
@@ -136,38 +150,72 @@ mrb_io_modestr_to_flags(mrb_state *mrb, const char *mode)
 }
 
 static int
-mrb_io_flags_to_modenum(mrb_state *mrb, int flags)
+mrb_io_mode_to_flags(mrb_state *mrb, mrb_value mode)
 {
-  int modenum = 0;
-
-  switch(flags & (FMODE_READABLE|FMODE_WRITABLE|FMODE_READWRITE)) {
-    case FMODE_READABLE:
-      modenum = O_RDONLY;
-      break;
-    case FMODE_WRITABLE:
-      modenum = O_WRONLY;
-      break;
-    case FMODE_READWRITE:
-      modenum = O_RDWR;
-      break;
-  }
-
-  if (flags & FMODE_APPEND) {
-    modenum |= O_APPEND;
-  }
-  if (flags & FMODE_TRUNC) {
-    modenum |= O_TRUNC;
+  if (mrb_nil_p(mode)) {
+    return mrb_io_modestr_to_flags(mrb, "r");
   }
-  if (flags & FMODE_CREATE) {
-    modenum |= O_CREAT;
+  else if (mrb_string_p(mode)) {
+    return mrb_io_modestr_to_flags(mrb, RSTRING_CSTR(mrb, mode));
   }
+  else {
+    int flags = 0;
+    mrb_int flags0 = mrb_int(mrb, mode);
+
+    switch (flags0 & MRB_O_ACCMODE) {
+      case MRB_O_RDONLY:
+        flags |= O_RDONLY;
+        break;
+      case MRB_O_WRONLY:
+        flags |= O_WRONLY;
+        break;
+      case MRB_O_RDWR:
+        flags |= O_RDWR;
+        break;
+      default:
+        mrb_raisef(mrb, E_ARGUMENT_ERROR, "illegal access mode %v", mode);
+    }
+
+    if (flags0 & MRB_O_APPEND)        flags |= O_APPEND;
+    if (flags0 & MRB_O_CREAT)         flags |= O_CREAT;
+    if (flags0 & MRB_O_EXCL)          flags |= O_EXCL;
+    if (flags0 & MRB_O_TRUNC)         flags |= O_TRUNC;
+#ifdef O_NONBLOCK
+    if (flags0 & MRB_O_NONBLOCK)      flags |= O_NONBLOCK;
+#endif
+#ifdef O_NOCTTY
+    if (flags0 & MRB_O_NOCTTY)        flags |= O_NOCTTY;
+#endif
 #ifdef O_BINARY
-  if (flags & FMODE_BINMODE) {
-    modenum |= O_BINARY;
-  }
+    if (flags0 & MRB_O_BINARY)        flags |= O_BINARY;
+#endif
+#ifdef O_SHARE_DELETE
+    if (flags0 & MRB_O_SHARE_DELETE)  flags |= O_SHARE_DELETE;
+#endif
+#ifdef O_SYNC
+    if (flags0 & MRB_O_SYNC)          flags |= O_SYNC;
+#endif
+#ifdef O_DSYNC
+    if (flags0 & MRB_O_DSYNC)         flags |= O_DSYNC;
+#endif
+#ifdef O_RSYNC
+    if (flags0 & MRB_O_RSYNC)         flags |= O_RSYNC;
+#endif
+#ifdef O_NOFOLLOW
+    if (flags0 & MRB_O_NOFOLLOW)      flags |= O_NOFOLLOW;
+#endif
+#ifdef O_NOATIME
+    if (flags0 & MRB_O_NOATIME)       flags |= O_NOATIME;
+#endif
+#ifdef O_DIRECT
+    if (flags0 & MRB_O_DIRECT)        flags |= O_DIRECT;
+#endif
+#ifdef O_TMPFILE
+    if (flags0 & MRB_O_TMPFILE)       flags |= O_TMPFILE;
 #endif
 
-  return modenum;
+    return flags;
+  }
 }
 
 static void
@@ -317,11 +365,11 @@ mrb_io_s_popen(mrb_state *mrb, mrb_value klass)
   ofd[0] = INVALID_HANDLE_VALUE;
   ofd[1] = INVALID_HANDLE_VALUE;
 
-  mrb_get_args(mrb, "S|SH", &cmd, &mode, &opt);
+  mrb_get_args(mrb, "S|oH", &cmd, &mode, &opt);
   io = mrb_obj_value(mrb_data_object_alloc(mrb, mrb_class_ptr(klass), NULL, &mrb_io_type));
 
   pname = RSTRING_CSTR(mrb, cmd);
-  flags = mrb_io_modestr_to_flags(mrb, RSTRING_CSTR(mrb, mode));
+  flags = mrb_io_mode_to_flags(mrb, mode);
 
   doexec = (strcmp("-", pname) != 0);
   opt_in = option_to_fd(mrb, opt, "in");
@@ -332,14 +380,14 @@ mrb_io_s_popen(mrb_state *mrb, mrb_value klass)
   saAttr.bInheritHandle = TRUE;
   saAttr.lpSecurityDescriptor = NULL;
 
-  if (flags & FMODE_READABLE) {
+  if (OPEN_READABLE_P(flags)) {
     if (!CreatePipe(&ofd[0], &ofd[1], &saAttr, 0)
         || !SetHandleInformation(ofd[0], HANDLE_FLAG_INHERIT, 0)) {
       mrb_sys_fail(mrb, "pipe");
     }
   }
 
-  if (flags & FMODE_WRITABLE) {
+  if (OPEN_WRITABLE_P(flags)) {
     if (!CreatePipe(&ifd[0], &ifd[1], &saAttr, 0)
         || !SetHandleInformation(ifd[1], HANDLE_FLAG_INHERIT, 0)) {
       mrb_sys_fail(mrb, "pipe");
@@ -353,11 +401,11 @@ mrb_io_s_popen(mrb_state *mrb, mrb_value klass)
     si.dwFlags |= STARTF_USESHOWWINDOW;
     si.wShowWindow = SW_HIDE;
     si.dwFlags |= STARTF_USESTDHANDLES;
-    if (flags & FMODE_READABLE) {
+    if (OPEN_READABLE_P(flags)) {
       si.hStdOutput = ofd[1];
       si.hStdError = ofd[1];
     }
-    if (flags & FMODE_WRITABLE) {
+    if (OPEN_WRITABLE_P(flags)) {
       si.hStdInput = ifd[0];
     }
     if (!CreateProcess(
@@ -381,8 +429,8 @@ mrb_io_s_popen(mrb_state *mrb, mrb_value klass)
   fptr->fd = _open_osfhandle((intptr_t)ofd[0], 0);
   fptr->fd2 = _open_osfhandle((intptr_t)ifd[1], 0);
   fptr->pid = pid;
-  fptr->readable = ((flags & FMODE_READABLE) != 0);
-  fptr->writable = ((flags & FMODE_WRITABLE) != 0);
+  fptr->readable = OPEN_READABLE_P(flags);
+  fptr->writable = OPEN_WRITABLE_P(flags);
   fptr->sync = 0;
 
   DATA_TYPE(io) = &mrb_io_type;
@@ -413,18 +461,18 @@ mrb_io_s_popen(mrb_state *mrb, mrb_value klass)
   int saved_errno;
   int opt_in, opt_out, opt_err;
 
-  mrb_get_args(mrb, "S|SH", &cmd, &mode, &opt);
+  mrb_get_args(mrb, "S|oH", &cmd, &mode, &opt);
   io = mrb_obj_value(mrb_data_object_alloc(mrb, mrb_class_ptr(klass), NULL, &mrb_io_type));
 
   pname = RSTRING_CSTR(mrb, cmd);
-  flags = mrb_io_modestr_to_flags(mrb, RSTRING_CSTR(mrb, mode));
+  flags = mrb_io_mode_to_flags(mrb, mode);
 
   doexec = (strcmp("-", pname) != 0);
   opt_in = option_to_fd(mrb, opt, "in");
   opt_out = option_to_fd(mrb, opt, "out");
   opt_err = option_to_fd(mrb, opt, "err");
 
-  if (flags & FMODE_READABLE) {
+  if (OPEN_READABLE_P(flags)) {
     if (pipe(pr) == -1) {
       mrb_sys_fail(mrb, "pipe");
     }
@@ -432,7 +480,7 @@ mrb_io_s_popen(mrb_state *mrb, mrb_value klass)
     mrb_fd_cloexec(mrb, pr[1]);
   }
 
-  if (flags & FMODE_WRITABLE) {
+  if (OPEN_WRITABLE_P(flags)) {
     if (pipe(pw) == -1) {
       if (pr[0] != -1) close(pr[0]);
       if (pr[1] != -1) close(pr[1]);
@@ -461,14 +509,14 @@ mrb_io_s_popen(mrb_state *mrb, mrb_value klass)
       if (opt_err != -1) {
         dup2(opt_err, 2);
       }
-      if (flags & FMODE_READABLE) {
+      if (OPEN_READABLE_P(flags)) {
         close(pr[0]);
         if (pr[1] != 1) {
           dup2(pr[1], 1);
           close(pr[1]);
         }
       }
-      if (flags & FMODE_WRITABLE) {
+      if (OPEN_WRITABLE_P(flags)) {
         close(pw[1]);
         if (pw[0] != 0) {
           dup2(pw[0], 0);
@@ -487,12 +535,12 @@ mrb_io_s_popen(mrb_state *mrb, mrb_value klass)
       break;
 
     default: /* parent */
-      if ((flags & FMODE_READABLE) && (flags & FMODE_WRITABLE)) {
+      if (OPEN_RDWR_P(flags)) {
         close(pr[1]);
         fd = pr[0];
         close(pw[0]);
         write_fd = pw[1];
-      } else if (flags & FMODE_READABLE) {
+      } else if (OPEN_RDONLY_P(flags)) {
         close(pr[1]);
         fd = pr[0];
       } else {
@@ -506,8 +554,8 @@ mrb_io_s_popen(mrb_state *mrb, mrb_value klass)
       fptr->fd = fd;
       fptr->fd2 = write_fd;
       fptr->pid = pid;
-      fptr->readable = ((flags & FMODE_READABLE) != 0);
-      fptr->writable = ((flags & FMODE_WRITABLE) != 0);
+      fptr->readable = OPEN_READABLE_P(flags);
+      fptr->writable = OPEN_WRITABLE_P(flags);
       fptr->sync = 0;
 
       DATA_TYPE(io) = &mrb_io_type;
@@ -517,11 +565,11 @@ mrb_io_s_popen(mrb_state *mrb, mrb_value klass)
 
     case -1: /* error */
       saved_errno = errno;
-      if (flags & FMODE_READABLE) {
+      if (OPEN_READABLE_P(flags)) {
         close(pr[0]);
         close(pr[1]);
       }
-      if (flags & FMODE_WRITABLE) {
+      if (OPEN_WRITABLE_P(flags)) {
         close(pw[0]);
         close(pw[1]);
       }
@@ -606,7 +654,7 @@ mrb_io_initialize(mrb_state *mrb, mrb_value io)
 
   mode = opt = mrb_nil_value();
 
-  mrb_get_args(mrb, "i|So", &fd, &mode, &opt);
+  mrb_get_args(mrb, "i|oo", &fd, &mode, &opt);
   if (mrb_nil_p(mode)) {
     mode = mrb_str_new_cstr(mrb, "r");
   }
@@ -614,7 +662,7 @@ mrb_io_initialize(mrb_state *mrb, mrb_value io)
     opt = mrb_hash_new(mrb);
   }
 
-  flags = mrb_io_modestr_to_flags(mrb, RSTRING_CSTR(mrb, mode));
+  flags = mrb_io_mode_to_flags(mrb, mode);
 
   mrb_iv_set(mrb, io, mrb_intern_cstr(mrb, "@buf"), mrb_str_new_cstr(mrb, ""));
 
@@ -629,8 +677,8 @@ mrb_io_initialize(mrb_state *mrb, mrb_value io)
   DATA_PTR(io) = fptr;
 
   fptr->fd = (int)fd;
-  fptr->readable = ((flags & FMODE_READABLE) != 0);
-  fptr->writable = ((flags & FMODE_WRITABLE) != 0);
+  fptr->readable = OPEN_READABLE_P(flags);
+  fptr->writable = OPEN_WRITABLE_P(flags);
   fptr->sync = 0;
   return io;
 }
@@ -785,20 +833,16 @@ mrb_io_s_sysopen(mrb_state *mrb, mrb_value klass)
   mrb_value mode = mrb_nil_value();
   mrb_int fd, perm = -1;
   const char *pat;
-  int flags, modenum;
+  int flags;
 
-  mrb_get_args(mrb, "S|Si", &path, &mode, &perm);
-  if (mrb_nil_p(mode)) {
-    mode = mrb_str_new_cstr(mrb, "r");
-  }
+  mrb_get_args(mrb, "S|oi", &path, &mode, &perm);
   if (perm < 0) {
     perm = 0666;
   }
 
   pat = RSTRING_CSTR(mrb, path);
-  flags = mrb_io_modestr_to_flags(mrb, RSTRING_CSTR(mrb, mode));
-  modenum = mrb_io_flags_to_modenum(mrb, flags);
-  fd = mrb_cloexec_open(mrb, pat, modenum, perm);
+  flags = mrb_io_mode_to_flags(mrb, mode);
+  fd = mrb_cloexec_open(mrb, pat, flags, perm);
   return mrb_fixnum_value(fd);
 }
 
diff --git a/mrbgems/mruby-io/test/mruby_io_test.c b/mrbgems/mruby-io/test/mruby_io_test.c
index 3cf1c6111..7e272d45a 100644
--- a/mrbgems/mruby-io/test/mruby_io_test.c
+++ b/mrbgems/mruby-io/test/mruby_io_test.c
@@ -1,3 +1,4 @@
+#include <mruby/common.h>
 #include <sys/types.h>
 #include <errno.h>
 
@@ -18,12 +19,6 @@ typedef int mode_t;
 #define open _open
 #define close _close
 
-#if defined(__MINGW64_VERSION_MAJOR)
-# define MRB_MINGW64_VERSION  (__MINGW64_VERSION_MAJOR * 1000 + __MINGW64_VERSION_MINOR)
-#elif defined(__MINGW32_MAJOR_VERSION)
-# define MRB_MINGW32_VERSION  (__MINGW32_MAJOR_VERSION * 1000 + __MINGW32_MINOR_VERSION)
-#endif
-
 #if defined(_MSC_VER) || \
     (defined(MRB_MINGW32_VERSION) && MRB_MINGW32_VERSION < 3021) || \
     (defined(MRB_MINGW64_VERSION) && MRB_MINGW64_VERSION < 4000)
diff --git a/mrbgems/mruby-socket/test/sockettest.c b/mrbgems/mruby-socket/test/sockettest.c
index 3017c7cc1..e9247d030 100644
--- a/mrbgems/mruby-socket/test/sockettest.c
+++ b/mrbgems/mruby-socket/test/sockettest.c
@@ -8,7 +8,9 @@
 
 #include <io.h>
 
-#ifdef _MSC_VER
+#if defined(_MSC_VER) || \
+    (defined(MRB_MINGW32_VERSION) && MRB_MINGW32_VERSION < 3021) || \
+    (defined(MRB_MINGW64_VERSION) && MRB_MINGW64_VERSION < 4000)
 
 #include <fcntl.h>
 #include <sys/stat.h>
diff --git a/mrbgems/mruby-time/src/time.c b/mrbgems/mruby-time/src/time.c
index 7197b634c..5ce43e465 100644
--- a/mrbgems/mruby-time/src/time.c
+++ b/mrbgems/mruby-time/src/time.c
@@ -238,7 +238,7 @@ mrb_to_time_t(mrb_state *mrb, mrb_value obj, time_t *usec)
         mrb_float f = mrb_float(obj);
 
         mrb_check_num_exact(mrb, f);
-        if (f > (mrb_float)MRB_TIME_MAX || (mrb_float)MRB_TIME_MIN > f) {
+        if (f >= ((mrb_float)MRB_TIME_MAX-1.0) || f < ((mrb_float)MRB_TIME_MIN+1.0)) {
           goto out_of_range;
         }
 
diff --git a/src/backtrace.c b/src/backtrace.c
index 186009523..591f4ea4b 100644
--- a/src/backtrace.c
+++ b/src/backtrace.c
@@ -79,7 +79,7 @@ each_backtrace(mrb_state *mrb, ptrdiff_t ciidx, const mrb_code *pc0, each_backtr
 static void
 print_backtrace(mrb_state *mrb, struct RObject *exc, mrb_value backtrace)
 {
-  int i;
+  mrb_int i;
   mrb_int n = RARRAY_LEN(backtrace);
   mrb_value *loc, mesg;
   FILE *stream = stderr;
@@ -89,7 +89,7 @@ print_backtrace(mrb_state *mrb, struct RObject *exc, mrb_value backtrace)
     for (i=n-1,loc=&RARRAY_PTR(backtrace)[i]; i>0; i--,loc--) {
       if (mrb_string_p(*loc)) {
         fprintf(stream, "\t[%d] %.*s\n",
-                i, (int)RSTRING_LEN(*loc), RSTRING_PTR(*loc));
+                (int)i, (int)RSTRING_LEN(*loc), RSTRING_PTR(*loc));
       }
     }
     if (mrb_string_p(*loc)) {
diff --git a/src/hash.c b/src/hash.c
index 70f437358..8e7f97147 100644
--- a/src/hash.c
+++ b/src/hash.c
@@ -222,9 +222,8 @@ static void
 ht_compact(mrb_state *mrb, htable *t)
 {
   segment *seg;
-  mrb_int i;
+  uint16_t i, i2;
   segment *seg2 = NULL;
-  mrb_int i2;
   mrb_int size = 0;
 
   if (t == NULL) return;
diff --git a/src/string.c b/src/string.c
index c7b9db17a..9ea19d107 100644
--- a/src/string.c
+++ b/src/string.c
@@ -504,25 +504,45 @@ str_index_str_by_char(mrb_state *mrb, mrb_value str, mrb_value sub, mrb_int pos)
 #define str_index_str_by_char(mrb, str, sub, pos) str_index_str(mrb, str, sub, pos)
 #endif
 
+#ifndef MRB_QS_SHORT_STRING_LENGTH
+#define MRB_QS_SHORT_STRING_LENGTH 2048
+#endif
+
 static inline mrb_int
 mrb_memsearch_qs(const unsigned char *xs, mrb_int m, const unsigned char *ys, mrb_int n)
 {
-  const unsigned char *x = xs, *xe = xs + m;
-  const unsigned char *y = ys;
-  int i;
-  ptrdiff_t qstable[256];
+  if (n + m < MRB_QS_SHORT_STRING_LENGTH) {
+    const unsigned char *y = ys;
+    const unsigned char *ye = ys+n-m+1;
 
-  /* Preprocessing */
-  for (i = 0; i < 256; ++i)
-    qstable[i] = m + 1;
-  for (; x < xe; ++x)
-    qstable[*x] = xe - x;
-  /* Searching */
-  for (; y + m <= ys + n; y += *(qstable + y[m])) {
-    if (*xs == *y && memcmp(xs, y, m) == 0)
-      return (mrb_int)(y - ys);
+    for (;;) {
+      y = (const unsigned char*)memchr(y, xs[0], (size_t)(ye-y));
+      if (y == NULL) return -1;
+      if (memcmp(xs, y, m) == 0) {
+        return (mrb_int)(y - ys);
+      }
+      y++;
+    }
+    return -1;
+  }
+  else {
+    const unsigned char *x = xs, *xe = xs + m;
+    const unsigned char *y = ys;
+    int i;
+    ptrdiff_t qstable[256];
+
+    /* Preprocessing */
+    for (i = 0; i < 256; ++i)
+      qstable[i] = m + 1;
+    for (; x < xe; ++x)
+      qstable[*x] = xe - x;
+    /* Searching */
+    for (; y + m <= ys + n; y += *(qstable + y[m])) {
+      if (*xs == *y && memcmp(xs, y, m) == 0)
+        return (mrb_int)(y - ys);
+    }
+    return -1;
   }
-  return -1;
 }
 
 static mrb_int
diff --git a/src/symbol.c b/src/symbol.c
index b8d0ea1e7..ad186dce3 100644
--- a/src/symbol.c
+++ b/src/symbol.c
@@ -48,14 +48,14 @@ sym_validate_len(mrb_state *mrb, size_t len)
 static const char pack_table[] = "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 
 static mrb_sym
-sym_inline_pack(const char *name, uint16_t len)
+sym_inline_pack(const char *name, size_t len)
 {
-  const int lower_length_max = (MRB_SYMBOL_BIT - 2) / 5;
-  const int mix_length_max   = (MRB_SYMBOL_BIT - 2) / 6;
+  const size_t lower_length_max = (MRB_SYMBOL_BIT - 2) / 5;
+  const size_t mix_length_max   = (MRB_SYMBOL_BIT - 2) / 6;
 
   char c;
   const char *p;
-  int i;
+  size_t i;
   mrb_sym sym = 0;
   mrb_bool lower = TRUE;
 
@@ -124,7 +124,7 @@ symhash(const char *key, size_t len)
 }
 
 static mrb_sym
-find_symbol(mrb_state *mrb, const char *name, uint16_t len, uint8_t *hashp)
+find_symbol(mrb_state *mrb, const char *name, size_t len, uint8_t *hashp)
 {
   mrb_sym i;
   symbol_name *sname;
diff --git a/src/vm.c b/src/vm.c
index 2ccc03e30..214907a19 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -1497,11 +1497,9 @@ RETRY_TRY_BLOCK:
       ci->target_class = MRB_PROC_TARGET_CLASS(m);
       ci->proc = m;
       if (MRB_PROC_ENV_P(m)) {
-        mrb_sym mid;
         struct REnv *e = MRB_PROC_ENV(m);
 
-        mid = e->mid;
-        if (mid) ci->mid = mid;
+        ci->mid = e->mid;
         if (!e->stack) {
           e->stack = mrb->c->stack;
         }
diff --git a/test/t/exception.rb b/test/t/exception.rb
index a6f69eef6..c9afeb61a 100644
--- a/test/t/exception.rb
+++ b/test/t/exception.rb
@@ -400,7 +400,7 @@ assert('GC in rescue') do
     end
   rescue => exception
     GC.start
-    assert_equal("#{__FILE__}:#{line}:in call",
+    assert_equal("#{__FILE__}:#{line}",
                  exception.backtrace.first)
   end
 end
@@ -418,7 +418,7 @@ assert('Method call in rescue') do
   rescue => exception
     [3].each do
     end
-    assert_equal("#{__FILE__}:#{line}:in call",
+    assert_equal("#{__FILE__}:#{line}",
                  exception.backtrace.first)
   end
 end