Constify `irep` members.

- `pool`
- `syms`
- `reps`

11 files changed, 105 insertions, 91 deletions

diff --git a/src/array.c b/src/array.c
index 71a957c9e..1337736f4 100644
--- a/src/array.c
+++ b/src/array.c
@@ -1309,14 +1309,16 @@ init_ary_each(mrb_state *mrb, struct RClass *ary)
   mrb_method_t m;
   mrb_irep *each_irep = (mrb_irep*)mrb_malloc(mrb, sizeof(mrb_irep));
   static const mrb_irep mrb_irep_zero = { 0 };
+  mrb_sym *syms;
 
   *each_irep = mrb_irep_zero;
-  each_irep->syms = (mrb_sym*)mrb_malloc(mrb, sizeof(mrb_sym)*5);
-  each_irep->syms[0] = MRB_SYM(each);
-  each_irep->syms[1] = MRB_SYM(to_enum);
-  each_irep->syms[2] = MRB_QSYM(aref);
-  each_irep->syms[3] = MRB_SYM(call);
-  each_irep->syms[4] = MRB_SYM(length);
+  syms = (mrb_sym*)mrb_malloc(mrb, sizeof(mrb_sym)*5);
+  syms[0] = MRB_SYM(each);
+  syms[1] = MRB_SYM(to_enum);
+  syms[2] = MRB_QSYM(aref);
+  syms[3] = MRB_SYM(call);
+  syms[4] = MRB_SYM(length);
+  each_irep->syms = syms;
   each_irep->slen = 5;
   each_irep->flags = MRB_ISEQ_NO_FREE;
   each_irep->iseq = each_iseq;
diff --git a/src/backtrace.c b/src/backtrace.c
index b614a04be..bcc188796 100644
--- a/src/backtrace.c
+++ b/src/backtrace.c
@@ -39,7 +39,7 @@ each_backtrace(mrb_state *mrb, ptrdiff_t ciidx, const mrb_code *pc0, each_backtr
   for (i=ciidx; i >= 0; i--) {
     struct backtrace_location loc;
     mrb_callinfo *ci;
-    mrb_irep *irep;
+    const mrb_irep *irep;
     const mrb_code *pc;
 
     ci = &mrb->c->cibase[i];
diff --git a/src/class.c b/src/class.c
index 2864fdda9..daba6f649 100644
--- a/src/class.c
+++ b/src/class.c
@@ -2315,12 +2315,14 @@ init_class_new(mrb_state *mrb, struct RClass *cls)
   struct RProc *p;
   mrb_method_t m;
   mrb_irep *new_irep = (mrb_irep*)mrb_malloc(mrb, sizeof(mrb_irep));
+  mrb_sym *syms;
   static const mrb_irep mrb_irep_zero = { 0 };
 
   *new_irep = mrb_irep_zero;
-  new_irep->syms = (mrb_sym*)mrb_malloc(mrb, sizeof(mrb_sym)*2);
-  new_irep->syms[0] = MRB_SYM(allocate);
-  new_irep->syms[1] = MRB_SYM(initialize);
+  syms = (mrb_sym*)mrb_malloc(mrb, sizeof(mrb_sym)*2);
+  syms[0] = MRB_SYM(allocate);
+  syms[1] = MRB_SYM(initialize);
+  new_irep->syms = syms;
   new_irep->slen = 2;
   new_irep->flags = MRB_ISEQ_NO_FREE;
   new_irep->iseq = new_iseq;
diff --git a/src/codedump.c b/src/codedump.c
index 649be176b..14cca8553 100644
--- a/src/codedump.c
+++ b/src/codedump.c
@@ -7,7 +7,7 @@
 
 #ifndef MRB_DISABLE_STDIO
 static void
-print_r(mrb_state *mrb, mrb_irep *irep, size_t n)
+print_r(mrb_state *mrb, const mrb_irep *irep, size_t n)
 {
   size_t i;
 
@@ -23,7 +23,7 @@ print_r(mrb_state *mrb, mrb_irep *irep, size_t n)
 }
 
 static void
-print_lv_a(mrb_state *mrb, mrb_irep *irep, uint16_t a)
+print_lv_a(mrb_state *mrb, const mrb_irep *irep, uint16_t a)
 {
   if (!irep->lv || a >= irep->nlocals || a == 0) {
     printf("\n");
@@ -35,7 +35,7 @@ print_lv_a(mrb_state *mrb, mrb_irep *irep, uint16_t a)
 }
 
 static void
-print_lv_ab(mrb_state *mrb, mrb_irep *irep, uint16_t a, uint16_t b)
+print_lv_ab(mrb_state *mrb, const mrb_irep *irep, uint16_t a, uint16_t b)
 {
   if (!irep->lv || (a >= irep->nlocals && b >= irep->nlocals) || a+b == 0) {
     printf("\n");
@@ -48,7 +48,7 @@ print_lv_ab(mrb_state *mrb, mrb_irep *irep, uint16_t a, uint16_t b)
 }
 
 static void
-print_header(mrb_state *mrb, mrb_irep *irep, ptrdiff_t i)
+print_header(mrb_state *mrb, const mrb_irep *irep, ptrdiff_t i)
 {
   int32_t line;
 
@@ -66,7 +66,7 @@ print_header(mrb_state *mrb, mrb_irep *irep, ptrdiff_t i)
 #define CASE(insn,ops) case insn: FETCH_ ## ops (); L_ ## insn
 
 static void
-codedump(mrb_state *mrb, mrb_irep *irep)
+codedump(mrb_state *mrb, const mrb_irep *irep)
 {
   int ai;
   const mrb_code *pc, *pcend;
@@ -533,7 +533,7 @@ codedump(mrb_state *mrb, mrb_irep *irep)
 }
 
 static void
-codedump_recur(mrb_state *mrb, mrb_irep *irep)
+codedump_recur(mrb_state *mrb, const mrb_irep *irep)
 {
   int i;
 
diff --git a/src/debug.c b/src/debug.c
index 32add68ae..dabc5a56d 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -51,7 +51,7 @@ select_line_type(const uint16_t *lines, size_t lines_len)
 }
 
 MRB_API char const*
-mrb_debug_get_filename(mrb_state *mrb, mrb_irep *irep, ptrdiff_t pc)
+mrb_debug_get_filename(mrb_state *mrb, const mrb_irep *irep, ptrdiff_t pc)
 {
   if (irep && pc >= 0 && pc < irep->ilen) {
     mrb_irep_debug_info_file* f = NULL;
diff --git a/src/dump.c b/src/dump.c
index a6bbe68f3..770c133fb 100644
--- a/src/dump.c
+++ b/src/dump.c
@@ -21,7 +21,7 @@
 #endif
 #endif
 
-static size_t get_irep_record_size_1(mrb_state *mrb, mrb_irep *irep);
+static size_t get_irep_record_size_1(mrb_state *mrb, const mrb_irep *irep);
 
 #if UINT32_MAX > SIZE_MAX
 # error This code cannot be built on your environment.
@@ -50,7 +50,7 @@ get_irep_header_size(mrb_state *mrb)
 }
 
 static ptrdiff_t
-write_irep_header(mrb_state *mrb, mrb_irep *irep, uint8_t *buf)
+write_irep_header(mrb_state *mrb, const mrb_irep *irep, uint8_t *buf)
 {
   uint8_t *cur = buf;
 
@@ -64,7 +64,7 @@ write_irep_header(mrb_state *mrb, mrb_irep *irep, uint8_t *buf)
 
 
 static size_t
-get_iseq_block_size(mrb_state *mrb, mrb_irep *irep)
+get_iseq_block_size(mrb_state *mrb, const mrb_irep *irep)
 {
   size_t size = 0;
 
@@ -76,7 +76,7 @@ get_iseq_block_size(mrb_state *mrb, mrb_irep *irep)
 }
 
 static ptrdiff_t
-write_iseq_block(mrb_state *mrb, mrb_irep *irep, uint8_t *buf, uint8_t flags)
+write_iseq_block(mrb_state *mrb, const mrb_irep *irep, uint8_t *buf, uint8_t flags)
 {
   uint8_t *cur = buf;
 
@@ -102,7 +102,7 @@ float_to_str(mrb_state *mrb, mrb_value flt)
 #endif
 
 static size_t
-get_pool_block_size(mrb_state *mrb, mrb_irep *irep)
+get_pool_block_size(mrb_state *mrb, const mrb_irep *irep)
 {
   int pool_no;
   size_t size = 0;
@@ -153,7 +153,7 @@ get_pool_block_size(mrb_state *mrb, mrb_irep *irep)
 }
 
 static ptrdiff_t
-write_pool_block(mrb_state *mrb, mrb_irep *irep, uint8_t *buf)
+write_pool_block(mrb_state *mrb, const mrb_irep *irep, uint8_t *buf)
 {
   int pool_no;
   uint8_t *cur = buf;
@@ -207,7 +207,7 @@ write_pool_block(mrb_state *mrb, mrb_irep *irep, uint8_t *buf)
 
 
 static size_t
-get_syms_block_size(mrb_state *mrb, mrb_irep *irep)
+get_syms_block_size(mrb_state *mrb, const mrb_irep *irep)
 {
   size_t size = 0;
   int sym_no;
@@ -226,7 +226,7 @@ get_syms_block_size(mrb_state *mrb, mrb_irep *irep)
 }
 
 static ptrdiff_t
-write_syms_block(mrb_state *mrb, mrb_irep *irep, uint8_t *buf)
+write_syms_block(mrb_state *mrb, const mrb_irep *irep, uint8_t *buf)
 {
   int sym_no;
   uint8_t *cur = buf;
@@ -255,7 +255,7 @@ write_syms_block(mrb_state *mrb, mrb_irep *irep, uint8_t *buf)
 }
 
 static size_t
-get_irep_record_size_1(mrb_state *mrb, mrb_irep *irep)
+get_irep_record_size_1(mrb_state *mrb, const mrb_irep *irep)
 {
   size_t size = 0;
 
@@ -267,7 +267,7 @@ get_irep_record_size_1(mrb_state *mrb, mrb_irep *irep)
 }
 
 static size_t
-get_irep_record_size(mrb_state *mrb, mrb_irep *irep)
+get_irep_record_size(mrb_state *mrb, const mrb_irep *irep)
 {
   size_t size = 0;
   int irep_no;
@@ -280,7 +280,7 @@ get_irep_record_size(mrb_state *mrb, mrb_irep *irep)
 }
 
 static int
-write_irep_record(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, size_t *irep_record_size, uint8_t flags)
+write_irep_record(mrb_state *mrb, const mrb_irep *irep, uint8_t *bin, size_t *irep_record_size, uint8_t flags)
 {
   int i;
   uint8_t *src = bin;
@@ -341,7 +341,7 @@ write_section_irep_header(mrb_state *mrb, size_t section_size, uint8_t *bin)
 }
 
 static int
-write_section_irep(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, size_t *len_p, uint8_t flags)
+write_section_irep(mrb_state *mrb, const mrb_irep *irep, uint8_t *bin, size_t *len_p, uint8_t flags)
 {
   int result;
   size_t rsize = 0;
@@ -364,7 +364,7 @@ write_section_irep(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, size_t *len_p,
 }
 
 static size_t
-get_debug_record_size(mrb_state *mrb, mrb_irep *irep)
+get_debug_record_size(mrb_state *mrb, const mrb_irep *irep)
 {
   size_t ret = 0;
   uint16_t f_idx;
@@ -413,11 +413,11 @@ find_filename_index(const mrb_sym *ary, int ary_len, mrb_sym s)
 }
 
 static size_t
-get_filename_table_size(mrb_state *mrb, mrb_irep *irep, mrb_sym **fp, uint16_t *lp)
+get_filename_table_size(mrb_state *mrb, const mrb_irep *irep, mrb_sym **fp, uint16_t *lp)
 {
   mrb_sym *filenames = *fp;
   size_t size = 0;
-  mrb_irep_debug_info *di = irep->debug_info;
+  const mrb_irep_debug_info *di = irep->debug_info;
   int i;
 
   mrb_assert(lp);
@@ -444,7 +444,7 @@ get_filename_table_size(mrb_state *mrb, mrb_irep *irep, mrb_sym **fp, uint16_t *
 }
 
 static size_t
-write_debug_record_1(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, mrb_sym const* filenames, uint16_t filenames_len)
+write_debug_record_1(mrb_state *mrb, const mrb_irep *irep, uint8_t *bin, mrb_sym const* filenames, uint16_t filenames_len)
 {
   uint8_t *cur;
   uint16_t f_idx;
@@ -498,7 +498,7 @@ write_debug_record_1(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, mrb_sym const
 }
 
 static size_t
-write_debug_record(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, mrb_sym const* filenames, uint16_t filenames_len)
+write_debug_record(mrb_state *mrb, const mrb_irep *irep, uint8_t *bin, mrb_sym const* filenames, uint16_t filenames_len)
 {
   size_t size, len;
   int irep_no;
@@ -516,7 +516,7 @@ write_debug_record(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, mrb_sym const*
 }
 
 static int
-write_section_debug(mrb_state *mrb, mrb_irep *irep, uint8_t *cur, mrb_sym const *filenames, uint16_t filenames_len)
+write_section_debug(mrb_state *mrb, const mrb_irep *irep, uint8_t *cur, mrb_sym const *filenames, uint16_t filenames_len)
 {
   size_t section_size = 0;
   const uint8_t *bin = cur;
@@ -632,7 +632,7 @@ write_lv_record(mrb_state *mrb, const mrb_irep *irep, uint8_t **start, mrb_sym c
 }
 
 static size_t
-get_lv_record_size(mrb_state *mrb, mrb_irep *irep)
+get_lv_record_size(mrb_state *mrb, const mrb_irep *irep)
 {
   size_t ret = 0;
   int i;
@@ -647,7 +647,7 @@ get_lv_record_size(mrb_state *mrb, mrb_irep *irep)
 }
 
 static size_t
-get_lv_section_size(mrb_state *mrb, mrb_irep *irep, mrb_sym const *syms, uint32_t syms_len)
+get_lv_section_size(mrb_state *mrb, const mrb_irep *irep, mrb_sym const *syms, uint32_t syms_len)
 {
   size_t ret = 0, i;
 
@@ -665,7 +665,7 @@ get_lv_section_size(mrb_state *mrb, mrb_irep *irep, mrb_sym const *syms, uint32_
 }
 
 static int
-write_section_lv(mrb_state *mrb, mrb_irep *irep, uint8_t *start, mrb_sym const *syms, uint32_t const syms_len)
+write_section_lv(mrb_state *mrb, const mrb_irep *irep, uint8_t *start, mrb_sym const *syms, uint32_t const syms_len)
 {
   uint8_t *cur = start;
   struct rite_section_lv_header *header;
@@ -721,7 +721,7 @@ write_rite_binary_header(mrb_state *mrb, size_t binary_size, uint8_t *bin, uint8
 }
 
 static mrb_bool
-debug_info_defined_p(mrb_irep *irep)
+debug_info_defined_p(const mrb_irep *irep)
 {
   int i;
 
@@ -733,7 +733,7 @@ debug_info_defined_p(mrb_irep *irep)
 }
 
 static mrb_bool
-lv_defined_p(mrb_irep *irep)
+lv_defined_p(const mrb_irep *irep)
 {
   int i;
 
@@ -747,7 +747,7 @@ lv_defined_p(mrb_irep *irep)
 }
 
 static int
-dump_irep(mrb_state *mrb, mrb_irep *irep, uint8_t flags, uint8_t **bin, size_t *bin_size)
+dump_irep(mrb_state *mrb, const mrb_irep *irep, uint8_t flags, uint8_t **bin, size_t *bin_size)
 {
   int result = MRB_DUMP_GENERAL_FAILURE;
   size_t malloc_size;
@@ -835,7 +835,7 @@ error_exit:
 }
 
 int
-mrb_dump_irep(mrb_state *mrb, mrb_irep *irep, uint8_t flags, uint8_t **bin, size_t *bin_size)
+mrb_dump_irep(mrb_state *mrb, const mrb_irep *irep, uint8_t flags, uint8_t **bin, size_t *bin_size)
 {
   return dump_irep(mrb, irep, flags, bin, bin_size);
 }
@@ -843,7 +843,7 @@ mrb_dump_irep(mrb_state *mrb, mrb_irep *irep, uint8_t flags, uint8_t **bin, size
 #ifndef MRB_DISABLE_STDIO
 
 int
-mrb_dump_irep_binary(mrb_state *mrb, mrb_irep *irep, uint8_t flags, FILE* fp)
+mrb_dump_irep_binary(mrb_state *mrb, const mrb_irep *irep, uint8_t flags, FILE* fp)
 {
   uint8_t *bin = NULL;
   size_t bin_size = 0;
@@ -865,7 +865,7 @@ mrb_dump_irep_binary(mrb_state *mrb, mrb_irep *irep, uint8_t flags, FILE* fp)
 }
 
 int
-mrb_dump_irep_cfunc(mrb_state *mrb, mrb_irep *irep, uint8_t flags, FILE *fp, const char *initname)
+mrb_dump_irep_cfunc(mrb_state *mrb, const mrb_irep *irep, uint8_t flags, FILE *fp, const char *initname)
 {
   uint8_t *bin = NULL;
   size_t bin_size = 0, bin_idx = 0;
diff --git a/src/gc.c b/src/gc.c
index 5531207db..897fa256f 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -868,7 +868,7 @@ obj_free(mrb_state *mrb, struct RBasic *obj, int end)
       struct RProc *p = (struct RProc*)obj;
 
       if (!MRB_PROC_CFUNC_P(p) && p->body.irep) {
-        mrb_irep *irep = p->body.irep;
+        mrb_irep *irep = (mrb_irep*)p->body.irep;
         if (end) {
           mrb_irep_cutref(mrb, irep);
         }
diff --git a/src/load.c b/src/load.c
index 247d511df..b033d7ad1 100644
--- a/src/load.c
+++ b/src/load.c
@@ -73,6 +73,8 @@ read_irep_record_1(mrb_state *mrb, const uint8_t *bin, size_t *len, uint8_t flag
   uint16_t tt, pool_data_len, snl;
   int plen;
   struct RData *irep_obj = mrb_data_object_alloc(mrb, mrb->object_class, NULL, &tempirep_type);
+  mrb_value *pool;
+  mrb_sym *syms;
   mrb_irep *irep = mrb_add_irep(mrb);
   int ai = mrb_gc_arena_save(mrb);
 
@@ -124,7 +126,7 @@ read_irep_record_1(mrb_state *mrb, const uint8_t *bin, size_t *len, uint8_t flag
     if (SIZE_ERROR_MUL(plen, sizeof(mrb_value))) {
       return NULL;
     }
-    irep->pool = (mrb_value*)mrb_malloc(mrb, sizeof(mrb_value) * plen);
+    irep->pool = pool = (mrb_value*)mrb_malloc(mrb, sizeof(mrb_value) * plen);
 
     for (i = 0; i < plen; i++) {
       const char *s;
@@ -139,26 +141,26 @@ read_irep_record_1(mrb_state *mrb, const uint8_t *bin, size_t *len, uint8_t flag
       case IREP_TT_FIXNUM: {
         mrb_value num = mrb_str_len_to_inum(mrb, s, pool_data_len, 10, FALSE);
 #ifdef MRB_WITHOUT_FLOAT
-        irep->pool[i] = num;
+        pool[i] = num;
 #else
-        irep->pool[i] = mrb_float_p(num)? mrb_float_pool(mrb, mrb_float(num)) : num;
+        pool[i] = mrb_float_p(num)? mrb_float_pool(mrb, mrb_float(num)) : num;
 #endif
         }
         break;
 
 #ifndef MRB_WITHOUT_FLOAT
       case IREP_TT_FLOAT:
-        irep->pool[i] = mrb_float_pool(mrb, str_to_double(mrb, s, pool_data_len));
+        pool[i] = mrb_float_pool(mrb, str_to_double(mrb, s, pool_data_len));
         break;
 #endif
 
       case IREP_TT_STRING:
-        irep->pool[i] = mrb_str_pool(mrb, s, pool_data_len, st);
+        pool[i] = mrb_str_pool(mrb, s, pool_data_len, st);
         break;
 
       default:
         /* should not happen */
-        irep->pool[i] = mrb_nil_value();
+        pool[i] = mrb_nil_value();
         break;
       }
       irep->plen++;
@@ -173,22 +175,22 @@ read_irep_record_1(mrb_state *mrb, const uint8_t *bin, size_t *len, uint8_t flag
     if (SIZE_ERROR_MUL(irep->slen, sizeof(mrb_sym))) {
       return NULL;
     }
-    irep->syms = (mrb_sym *)mrb_malloc(mrb, sizeof(mrb_sym) * irep->slen);
+    irep->syms = syms = (mrb_sym *)mrb_malloc(mrb, sizeof(mrb_sym) * irep->slen);
 
     for (i = 0; i < irep->slen; i++) {
       snl = bin_to_uint16(src);               /* symbol name length */
       src += sizeof(uint16_t);
 
       if (snl == MRB_DUMP_NULL_SYM_LEN) {
-        irep->syms[i] = 0;
+        syms[i] = 0;
         continue;
       }
 
       if (flags & FLAG_SRC_MALLOC) {
-        irep->syms[i] = mrb_intern(mrb, (char *)src, snl);
+        syms[i] = mrb_intern(mrb, (char *)src, snl);
       }
       else {
-        irep->syms[i] = mrb_intern_static(mrb, (char *)src, snl);
+        syms[i] = mrb_intern_static(mrb, (char *)src, snl);
       }
       src += snl + 1;
 
@@ -196,8 +198,6 @@ read_irep_record_1(mrb_state *mrb, const uint8_t *bin, size_t *len, uint8_t flag
     }
   }
 
-  irep->reps = (mrb_irep**)mrb_calloc(mrb, irep->rlen, sizeof(mrb_irep*));
-
   diff = src - bin;
   mrb_assert_int_fit(ptrdiff_t, diff, size_t, SIZE_MAX);
   *len = (size_t)diff;
@@ -214,21 +214,24 @@ read_irep_record(mrb_state *mrb, const uint8_t *bin, size_t *len, uint8_t flags)
   int ai = mrb_gc_arena_save(mrb);
   mrb_irep *irep = read_irep_record_1(mrb, bin, len, flags);
   int i;
+  mrb_irep **reps;
 
   mrb_gc_arena_restore(mrb, ai);
   if (irep == NULL) {
     return NULL;
   }
 
+  reps = (mrb_irep**)mrb_calloc(mrb, irep->rlen, sizeof(mrb_irep*));
+  irep->reps = (const mrb_irep**)reps;
   irep_obj->data = irep;
 
   bin += *len;
   for (i=0; i<irep->rlen; i++) {
     size_t rlen;
 
-    irep->reps[i] = read_irep_record(mrb, bin, &rlen, flags);
+    reps[i] = read_irep_record(mrb, bin, &rlen, flags);
     mrb_gc_arena_restore(mrb, ai);
-    if (irep->reps[i] == NULL) {
+    if (reps[i] == NULL) {
       return NULL;
     }
     bin += rlen;
@@ -257,25 +260,26 @@ read_debug_record(mrb_state *mrb, const uint8_t *start, mrb_irep* irep, size_t *
   size_t record_size;
   uint16_t f_idx;
   int i;
+  mrb_irep_debug_info *debug;
 
   if (irep->debug_info) { return MRB_DUMP_INVALID_IREP; }
 
-  irep->debug_info = (mrb_irep_debug_info*)mrb_calloc(mrb, 1, sizeof(mrb_irep_debug_info));
-  irep->debug_info->pc_count = (uint32_t)irep->ilen;
+  irep->debug_info = debug = (mrb_irep_debug_info*)mrb_calloc(mrb, 1, sizeof(mrb_irep_debug_info));
+  debug->pc_count = (uint32_t)irep->ilen;
 
   record_size = (size_t)bin_to_uint32(bin);
   bin += sizeof(uint32_t);
 
-  irep->debug_info->flen = bin_to_uint16(bin);
-  irep->debug_info->files = (mrb_irep_debug_info_file**)mrb_calloc(mrb, irep->debug_info->flen, sizeof(mrb_irep_debug_info*));
+  debug->flen = bin_to_uint16(bin);
+  debug->files = (mrb_irep_debug_info_file**)mrb_calloc(mrb, irep->debug_info->flen, sizeof(mrb_irep_debug_info*));
   bin += sizeof(uint16_t);
 
-  for (f_idx = 0; f_idx < irep->debug_info->flen; ++f_idx) {
+  for (f_idx = 0; f_idx < debug->flen; ++f_idx) {
     mrb_irep_debug_info_file *file;
     uint16_t filename_idx;
 
     file = (mrb_irep_debug_info_file *)mrb_calloc(mrb, 1, sizeof(*file));
-    irep->debug_info->files[f_idx] = file;
+    debug->files[f_idx] = file;
 
     file->start_pos = bin_to_uint32(bin);
     bin += sizeof(uint32_t);
@@ -329,7 +333,7 @@ read_debug_record(mrb_state *mrb, const uint8_t *start, mrb_irep* irep, size_t *
     size_t len;
     int ret;
 
-    ret = read_debug_record(mrb, bin, irep->reps[i], &len, filenames, filenames_len);
+    ret = read_debug_record(mrb, bin, (mrb_irep*)irep->reps[i], &len, filenames, filenames_len);
     if (ret != MRB_DUMP_OK) return ret;
     bin += len;
   }
@@ -393,25 +397,26 @@ static int
 read_lv_record(mrb_state *mrb, const uint8_t *start, mrb_irep *irep, size_t *record_len, mrb_sym const *syms, uint32_t syms_len)
 {
   const uint8_t *bin = start;
+  struct mrb_locals *lv;
   ptrdiff_t diff;
   int i;
 
-  irep->lv = (struct mrb_locals*)mrb_malloc(mrb, sizeof(struct mrb_locals) * (irep->nlocals - 1));
+  irep->lv = lv = (struct mrb_locals*)mrb_malloc(mrb, sizeof(struct mrb_locals) * (irep->nlocals - 1));
 
   for (i = 0; i + 1< irep->nlocals; ++i) {
     uint16_t const sym_idx = bin_to_uint16(bin);
     bin += sizeof(uint16_t);
     if (sym_idx == RITE_LV_NULL_MARK) {
-      irep->lv[i].name = 0;
-      irep->lv[i].r = 0;
+      lv[i].name = 0;
+      lv[i].r = 0;
     }
     else {
       if (sym_idx >= syms_len) {
         return MRB_DUMP_GENERAL_FAILURE;
       }
-      irep->lv[i].name = syms[sym_idx];
+      lv[i].name = syms[sym_idx];
 
-      irep->lv[i].r = bin_to_uint16(bin);
+      lv[i].r = bin_to_uint16(bin);
     }
     bin += sizeof(uint16_t);
   }
@@ -420,7 +425,7 @@ read_lv_record(mrb_state *mrb, const uint8_t *start, mrb_irep *irep, size_t *rec
     size_t len;
     int ret;
 
-    ret = read_lv_record(mrb, bin, irep->reps[i], &len, syms, syms_len);
+    ret = read_lv_record(mrb, bin, (mrb_irep*)irep->reps[i], &len, syms, syms_len);
     if (ret != MRB_DUMP_OK) return ret;
     bin += len;
   }
diff --git a/src/proc.c b/src/proc.c
index 36e7a5652..2a980620b 100644
--- a/src/proc.c
+++ b/src/proc.c
@@ -15,7 +15,7 @@ static const mrb_code call_iseq[] = {
 };
 
 struct RProc*
-mrb_proc_new(mrb_state *mrb, mrb_irep *irep)
+mrb_proc_new(mrb_state *mrb, const mrb_irep *irep)
 {
   struct RProc *p;
   mrb_callinfo *ci = mrb->c->ci;
@@ -34,7 +34,7 @@ mrb_proc_new(mrb_state *mrb, mrb_irep *irep)
     p->e.target_class = tc;
   }
   p->body.irep = irep;
-  mrb_irep_incref(mrb, irep);
+  mrb_irep_incref(mrb, (mrb_irep*)irep);
 
   return p;
 }
@@ -90,7 +90,7 @@ closure_setup(mrb_state *mrb, struct RProc *p)
 }
 
 struct RProc*
-mrb_closure_new(mrb_state *mrb, mrb_irep *irep)
+mrb_closure_new(mrb_state *mrb, const mrb_irep *irep)
 {
   struct RProc *p = mrb_proc_new(mrb, irep);
 
@@ -181,7 +181,7 @@ mrb_proc_copy(struct RProc *a, struct RProc *b)
   a->flags = b->flags;
   a->body = b->body;
   if (!MRB_PROC_CFUNC_P(a) && a->body.irep) {
-    a->body.irep->refcnt++;
+    mrb_irep_incref(NULL, (mrb_irep*)a->body.irep);
   }
   a->upper = b->upper;
   a->e.env = b->e.env;
@@ -262,7 +262,7 @@ proc_lambda(mrb_state *mrb, mrb_value self)
 mrb_int
 mrb_proc_arity(const struct RProc *p)
 {
-  struct mrb_irep *irep;
+  const mrb_irep *irep;
   const mrb_code *pc;
   mrb_aspec aspec;
   int ma, op, ra, pa, arity;
diff --git a/src/state.c b/src/state.c
index 790f7ca13..323532363 100644
--- a/src/state.c
+++ b/src/state.c
@@ -107,12 +107,14 @@ void mrb_free_symtbl(mrb_state *mrb);
 void
 mrb_irep_incref(mrb_state *mrb, mrb_irep *irep)
 {
+  if (irep->flags & MRB_IREP_NO_FREE) return;
   irep->refcnt++;
 }
 
 void
 mrb_irep_decref(mrb_state *mrb, mrb_irep *irep)
 {
+  if (irep->flags & MRB_IREP_NO_FREE) return;
   irep->refcnt--;
   if (irep->refcnt == 0) {
     mrb_irep_free(mrb, irep);
@@ -122,12 +124,14 @@ mrb_irep_decref(mrb_state *mrb, mrb_irep *irep)
 void
 mrb_irep_cutref(mrb_state *mrb, mrb_irep *irep)
 {
-  mrb_irep *tmp;
+  mrb_irep **reps;
   int i;
 
+  if (irep->flags & MRB_IREP_NO_FREE) return;
+  reps = (mrb_irep**)irep->reps;
   for (i=0; i<irep->rlen; i++) {
-    tmp = irep->reps[i];
-    irep->reps[i] = NULL;
+    mrb_irep *tmp = reps[i];
+    reps[i] = NULL;
     if (tmp) mrb_irep_decref(mrb, tmp);
   }
 }
@@ -137,6 +141,7 @@ mrb_irep_free(mrb_state *mrb, mrb_irep *irep)
 {
   int i;
 
+  if (irep->flags & MRB_IREP_NO_FREE) return;
   if (!(irep->flags & MRB_ISEQ_NO_FREE))
     mrb_free(mrb, (void*)irep->iseq);
   if (irep->pool) for (i=0; i<irep->plen; i++) {
@@ -150,16 +155,16 @@ mrb_irep_free(mrb_state *mrb, mrb_irep *irep)
     }
 #endif
   }
-  mrb_free(mrb, irep->pool);
-  mrb_free(mrb, irep->syms);
+  mrb_free(mrb, (void*)irep->pool);
+  mrb_free(mrb, (void*)irep->syms);
   if (irep->reps) {
     for (i=0; i<irep->rlen; i++) {
       if (irep->reps[i])
-        mrb_irep_decref(mrb, irep->reps[i]);
+        mrb_irep_decref(mrb, (mrb_irep*)irep->reps[i]);
     }
+    mrb_free(mrb, (void*)irep->reps);
   }
-  mrb_free(mrb, irep->reps);
-  mrb_free(mrb, irep->lv);
+  mrb_free(mrb, (void*)irep->lv);
   mrb_debug_info_free(mrb, irep->debug_info);
   mrb_free(mrb, irep);
 }
diff --git a/src/vm.c b/src/vm.c
index 689c5b85e..064086fb9 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -920,7 +920,7 @@ argnum_error(mrb_state *mrb, mrb_int num)
 MRB_API mrb_value
 mrb_vm_run(mrb_state *mrb, struct RProc *proc, mrb_value self, unsigned int stack_keep)
 {
-  mrb_irep *irep = proc->body.irep;
+  const mrb_irep *irep = proc->body.irep;
   mrb_value result;
   struct mrb_context *c = mrb->c;
   ptrdiff_t cioff = c->ci - c->cibase;
@@ -965,9 +965,9 @@ mrb_vm_exec(mrb_state *mrb, struct RProc *proc, const mrb_code *pc)
 {
   /* mrb_assert(MRB_PROC_CFUNC_P(proc)) */
   const mrb_code *pc0 = pc;
-  mrb_irep *irep = proc->body.irep;
-  mrb_value *pool = irep->pool;
-  mrb_sym *syms = irep->syms;
+  const mrb_irep *irep = proc->body.irep;
+  const mrb_value *pool = irep->pool;
+  const mrb_sym *syms = irep->syms;
   mrb_code insn;
   int ai = mrb_gc_arena_save(mrb);
   struct mrb_jmpbuf *prev_jmp = mrb->jmp;
@@ -2549,7 +2549,7 @@ RETRY_TRY_BLOCK:
     L_MAKE_LAMBDA:
     {
       struct RProc *p;
-      mrb_irep *nirep = irep->reps[b];
+      const mrb_irep *nirep = irep->reps[b];
 
       if (c & OP_L_CAPTURE) {
         p = mrb_closure_new(mrb, nirep);
@@ -2627,7 +2627,7 @@ RETRY_TRY_BLOCK:
     CASE(OP_EXEC, BB) {
       mrb_value recv = regs[a];
       struct RProc *p;
-      mrb_irep *nirep = irep->reps[b];
+      const mrb_irep *nirep = irep->reps[b];
 
       /* prepare closure */
       p = mrb_proc_new(mrb, nirep);