constify pointer from RARRAY_PTR to detect potential write barrier bugs.

if you see compiler errors due to this commit, you'd better to use array-modifying
functions, e.g. mrb_ary_set() or mrb_ary_push(), otherwise you might see nasty
GC bugs in the future.  if you are sure what you are doing, replace `RARRAY_PTR(ary)`
by `mrb_ary_ptr(ary)->ptr`. but be warned.

include/mruby/array.h

@@ -32,7 +32,7 @@ struct RArray {
 #define RARRAY(v)  ((struct RArray*)(mrb_ptr(v)))
 
 #define RARRAY_LEN(a) (RARRAY(a)->len)
-#define RARRAY_PTR(a) (RARRAY(a)->ptr)
+#define RARRAY_PTR(a) ((const mrb_value*)RARRAY(a)->ptr)
 #define MRB_ARY_SHARED      256
 #define ARY_SHARED_P(a) ((a)->flags & MRB_ARY_SHARED)
 #define ARY_SET_SHARED_FLAG(a) ((a)->flags |= MRB_ARY_SHARED)

mrbgems/mruby-random/src/random.c

@@ -221,8 +221,8 @@ mrb_ary_shuffle_bang(mrb_state *mrb, mrb_value ary)
       j = mrb_fixnum(mrb_random_mt_rand(mrb, random, mrb_fixnum_value(RARRAY_LEN(ary))));
 
       tmp = RARRAY_PTR(ary)[i];
-      RARRAY_PTR(ary)[i] = RARRAY_PTR(ary)[j];
-      RARRAY_PTR(ary)[j] = tmp;
+      mrb_ary_ptr(ary)->ptr[i] = RARRAY_PTR(ary)[j];
+      mrb_ary_ptr(ary)->ptr[j] = tmp;
     }
   }
 
@@ -305,11 +305,10 @@ mrb_ary_sample(mrb_state *mrb, mrb_value ary)
         }
         break;
       }
-      RARRAY_PTR(result)[i] = mrb_fixnum_value(r);
-      RARRAY_LEN(result)++;
+      mrb_ary_push(mrb, result, mrb_fixnum_value(r));
     }
     for (i=0; i<n; i++) {
-      RARRAY_PTR(result)[i] = RARRAY_PTR(ary)[mrb_fixnum(RARRAY_PTR(result)[i])];
+      mrb_ary_set(mrb, result, i, RARRAY_PTR(ary)[mrb_fixnum(RARRAY_PTR(result)[i])]);
     }
     return result;
   }

mrbgems/mruby-struct/src/struct.c

@@ -14,8 +14,8 @@
 #include "mruby/hash.h"
 #include "mruby/range.h"
 
-#define RSTRUCT_LEN(st) RARRAY_LEN(st)
-#define RSTRUCT_PTR(st) RARRAY_PTR(st)
+#define RSTRUCT_LEN(st) mrb_ary_ptr(st)->len
+#define RSTRUCT_PTR(st) mrb_ary_ptr(st)->ptr
 
 static struct RClass *
 struct_class(mrb_state *mrb)
@@ -72,15 +72,10 @@ static mrb_value
 mrb_struct_s_members_m(mrb_state *mrb, mrb_value klass)
 {
   mrb_value members, ary;
-  mrb_value *p, *pend;
 
   members = mrb_struct_s_members(mrb, klass);
   ary = mrb_ary_new_capa(mrb, RARRAY_LEN(members));
-  p = RARRAY_PTR(members); pend = p + RARRAY_LEN(members);
-  while (p < pend) {
-    mrb_ary_push(mrb, ary, *p);
-    p++;
-  }
+  mrb_ary_replace(mrb, ary, members);
   return ary;
 }
 
@@ -106,7 +101,8 @@ mrb_struct_members_m(mrb_state *mrb, mrb_value obj)
 static mrb_value
 mrb_struct_getmember(mrb_state *mrb, mrb_value obj, mrb_sym id)
 {
-  mrb_value members, slot, *ptr, *ptr_members;
+  mrb_value members, slot, *ptr;
+  const mrb_value *ptr_members;
   mrb_int i, len;
 
   ptr = RSTRUCT_PTR(obj);
@@ -181,7 +177,8 @@ mrb_struct_set(mrb_state *mrb, mrb_value obj, mrb_value val)
   const char *name;
   mrb_int i, len, slen;
   mrb_sym mid;
-  mrb_value members, slot, *ptr, *ptr_members;
+  mrb_value members, slot, *ptr;
+  const mrb_value *ptr_members;
 
   /* get base id */
   name = mrb_sym2name_len(mrb, mrb->c->ci->mid, &slen);
@@ -227,7 +224,7 @@ is_const_id(mrb_state *mrb, const char *name)
 static void
 make_struct_define_accessors(mrb_state *mrb, mrb_value members, struct RClass *c)
 {
-  mrb_value *ptr_members = RARRAY_PTR(members);
+  const mrb_value *ptr_members = RARRAY_PTR(members);
   mrb_int i;
   mrb_int len = RARRAY_LEN(members);
   int ai = mrb_gc_arena_save(mrb);
@@ -359,7 +356,7 @@ mrb_struct_s_def(mrb_state *mrb, mrb_value klass)
     }
     for (i=0; i<RARRAY_LEN(rest); i++) {
       id = mrb_obj_to_sym(mrb, RARRAY_PTR(rest)[i]);
-      RARRAY_PTR(rest)[i] = mrb_symbol_value(id);
+      mrb_ary_set(mrb, rest, i, mrb_symbol_value(id));
     }
   }
   st = make_struct(mrb, name, rest, struct_class(mrb));
@@ -420,7 +417,8 @@ inspect_struct(mrb_state *mrb, mrb_value s, mrb_bool recur)
 {
   const char *cn = mrb_class_name(mrb, mrb_obj_class(mrb, s));
   mrb_value members, str = mrb_str_new_lit(mrb, "#<struct ");
-  mrb_value *ptr, *ptr_members;
+  mrb_value *ptr;
+  const mrb_value *ptr_members;
   mrb_int i, len;
 
   if (cn) {
@@ -506,7 +504,8 @@ mrb_struct_init_copy(mrb_state *mrb, mrb_value copy)
 static mrb_value
 struct_aref_sym(mrb_state *mrb, mrb_value s, mrb_sym id)
 {
-  mrb_value *ptr, members, *ptr_members;
+  mrb_value *ptr, members;
+  const mrb_value *ptr_members;
   mrb_int i, len;
 
   ptr = RSTRUCT_PTR(s);
@@ -579,7 +578,8 @@ mrb_struct_aref(mrb_state *mrb, mrb_value s)
 static mrb_value
 mrb_struct_aset_sym(mrb_state *mrb, mrb_value s, mrb_sym id, mrb_value val)
 {
-  mrb_value members, *ptr, *ptr_members;
+  mrb_value members, *ptr;
+  const mrb_value *ptr_members;
   mrb_int i, len;
 
   members = mrb_struct_members(mrb, s);

src/array.c

@@ -574,7 +574,7 @@ mrb_ary_splice(mrb_state *mrb, mrb_value ary, mrb_int head, mrb_int len, mrb_val
 {
   struct RArray *a = mrb_ary_ptr(ary);
   mrb_int tail, size;
-  mrb_value *argv;
+  const mrb_value *argv;
   mrb_int i, argc;
 
   ary_modify(mrb, a);

src/hash.c

@@ -698,12 +698,13 @@ mrb_hash_keys(mrb_state *mrb, mrb_value hash)
 {
   khash_t(ht) *h = RHASH_TBL(hash);
   khiter_t k;
-  mrb_value ary, *p;
+  mrb_value ary;
+  mrb_value *p;
 
   if (!h || kh_size(h) == 0) return mrb_ary_new(mrb);
   ary = mrb_ary_new_capa(mrb, kh_size(h));
   mrb_ary_set(mrb, ary, kh_size(h)-1, mrb_nil_value());
-  p = RARRAY_PTR(ary);
+  p = mrb_ary_ptr(ary)->ptr;
   for (k = kh_begin(h); k != kh_end(h); k++) {
     if (kh_exist(h, k)) {
       mrb_value kv = kh_key(h, k);