Avoid direct access to error messages as instance variables

ref. #2485

The `SystemCallError#to_s` method also needed to be modified, but since it has no functional difference from the `Exception#to_s` method, it will be removed.

include/mruby/error.h

@@ -30,6 +30,8 @@ MRB_API mrb_value mrb_exc_new_str(mrb_state *mrb, struct RClass* c, mrb_value st
 MRB_API mrb_value mrb_make_exception(mrb_state *mrb, mrb_int argc, const mrb_value *argv);
 mrb_value mrb_exc_backtrace(mrb_state *mrb, mrb_value exc);
 mrb_value mrb_get_backtrace(mrb_state *mrb);
+void mrb_exc_mesg_set(mrb_state *mrb, struct RException *exc, mrb_value mesg);
+mrb_value mrb_exc_mesg_get(mrb_state *mrb, struct RException *exc);
 
 MRB_API mrb_noreturn void mrb_no_method_error(mrb_state *mrb, mrb_sym id, mrb_value args, const char *fmt, ...);
 

mrbgems/mruby-errno/src/errno.c

 #include "mruby.h"
 #include "mruby/array.h"
 #include "mruby/class.h"
+#include "mruby/error.h"
 #include "mruby/hash.h"
 #include "mruby/numeric.h"
 #include "mruby/string.h"
@@ -51,7 +52,7 @@ mrb_sce_init(mrb_state *mrb, mrb_value self, mrb_value m, mrb_int n)
     mrb_str_cat2(mrb, str, " - ");
     mrb_str_append(mrb, str, m);
   }
-  mrb_iv_set(mrb, self, MRB_SYM(mesg), str);
+  mrb_exc_mesg_set(mrb, mrb_exc_ptr(self), str);
 }
 
 static mrb_value
@@ -89,12 +90,6 @@ mrb_sce_errno(mrb_state *mrb, mrb_value self)
   }
 }
 
-static mrb_value
-mrb_sce_to_s(mrb_state *mrb, mrb_value self)
-{
-  return mrb_attr_get(mrb, self, MRB_SYM(mesg));
-}
-
 static mrb_value
 mrb_sce_sys_fail(mrb_state *mrb, mrb_value cls)
 {
@@ -132,7 +127,7 @@ mrb_exxx_init(mrb_state *mrb, mrb_value self)
     mrb_str_cat2(mrb, str, " - ");
     mrb_str_append(mrb, str, m);
   }
-  mrb_iv_set(mrb, self, MRB_SYM(mesg), str);
+  mrb_exc_mesg_set(mrb, mrb_exc_ptr(self), str);
   return self;
 }
 
@@ -147,7 +142,6 @@ mrb_mruby_errno_gem_init(mrb_state *mrb)
   sce = mrb_define_class(mrb, "SystemCallError", ste);
   mrb_define_class_method(mrb, sce, "_sys_fail", mrb_sce_sys_fail, MRB_ARGS_REQ(1));
   mrb_define_method(mrb, sce, "errno", mrb_sce_errno, MRB_ARGS_NONE());
-  mrb_define_method(mrb, sce, "to_s", mrb_sce_to_s, MRB_ARGS_NONE());
   mrb_define_method(mrb, sce, "initialize", mrb_sce_init_m, MRB_ARGS_ARG(1, 1));
 
   eno = mrb_define_module_id(mrb, MRB_SYM(Errno));

src/error.c

@@ -17,8 +17,8 @@
 #include <mruby/throw.h>
 #include <mruby/presym.h>
 
-static void
-exc_mesg_set(mrb_state *mrb, struct RException *exc, mrb_value mesg)
+void
+mrb_exc_mesg_set(mrb_state *mrb, struct RException *exc, mrb_value mesg)
 {
   if (mrb_string_p(mesg)) {
     exc->flags |= MRB_EXC_MESG_STRING_FLAG;
@@ -36,8 +36,8 @@ exc_mesg_set(mrb_state *mrb, struct RException *exc, mrb_value mesg)
   }
 }
 
-static mrb_value
-exc_mesg_get(mrb_state *mrb, struct RException *exc)
+mrb_value
+mrb_exc_mesg_get(mrb_state *mrb, struct RException *exc)
 {
   if ((exc->flags & MRB_EXC_MESG_STRING_FLAG) != 0) {
     return mrb_obj_value(exc->mesg);
@@ -52,9 +52,9 @@ mrb_exc_new_str(mrb_state *mrb, struct RClass* c, mrb_value str)
 {
   mrb_ensure_string_type(mrb, str);
 
-  struct RBasic* e = mrb_obj_alloc(mrb, MRB_TT_EXCEPTION, c);
+  struct RException *e = MRB_OBJ_ALLOC(mrb, MRB_TT_EXCEPTION, c);
   mrb_value exc = mrb_obj_value(e);
-  mrb_iv_set(mrb, exc, MRB_SYM(mesg), str);
+  mrb_exc_mesg_set(mrb, e, str);
   return exc;
 }
 
@@ -78,7 +78,7 @@ exc_initialize(mrb_state *mrb, mrb_value exc)
   mrb_value mesg;
 
   if (mrb_get_args(mrb, "|o", &mesg) == 1) {
-    exc_mesg_set(mrb, mrb_exc_ptr(exc), mesg);
+    mrb_exc_mesg_set(mrb, mrb_exc_ptr(exc), mesg);
   }
   return exc;
 }
@@ -107,7 +107,7 @@ exc_exception(mrb_state *mrb, mrb_value self)
   if (argc == 0) return self;
   if (mrb_obj_equal(mrb, self, a)) return self;
   exc = mrb_obj_clone(mrb, self);
-  exc_mesg_set(mrb, mrb_exc_ptr(exc), a);
+  mrb_exc_mesg_set(mrb, mrb_exc_ptr(exc), a);
 
   return exc;
 }
@@ -123,7 +123,7 @@ exc_exception(mrb_state *mrb, mrb_value self)
 static mrb_value
 exc_to_s(mrb_state *mrb, mrb_value exc)
 {
-  mrb_value mesg = exc_mesg_get(mrb, mrb_exc_ptr(exc));
+  mrb_value mesg = mrb_exc_mesg_get(mrb, mrb_exc_ptr(exc));
   struct RObject *p;
 
   if (!mrb_string_p(mesg)) {
@@ -163,7 +163,7 @@ exc_message(mrb_state *mrb, mrb_value exc)
 mrb_value
 mrb_exc_inspect(mrb_state *mrb, mrb_value exc)
 {
-  mrb_value mesg = exc_mesg_get(mrb, mrb_exc_ptr(exc));
+  mrb_value mesg = mrb_exc_mesg_get(mrb, mrb_exc_ptr(exc));
   mrb_value cname = mrb_mod_to_s(mrb, mrb_obj_value(mrb_obj_class(mrb, exc)));
   mesg = mrb_obj_as_string(mrb, mesg);
   return RSTRING_LEN(mesg) == 0 ? cname : mrb_format(mrb, "%v (%v)", mesg, cname);