vm_insnhelper.c: raise ruby_error_sysstack_gc

* vm_insnhelper.c (rb_threadptr_stack_overflow): rb_fatal is not
  available during GC.  raise the preallocated fatal error.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59618 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

eval.c

@@ -1930,6 +1930,7 @@ Init_eval(void)
     rb_define_global_function("untrace_var", rb_f_untrace_var, -1);	/* in variable.c */
 
     rb_vm_register_special_exception(ruby_error_reenter, rb_eFatal, "exception reentered");
+    rb_vm_register_special_exception(ruby_error_sysstack_gc, rb_eFatal, "machine stack overflow while GC is running.");
 
     id_signo = rb_intern_const("signo");
     id_status = rb_intern_const("status");

vm_core.h

@@ -455,6 +455,7 @@ enum ruby_special_exceptions {
     ruby_error_reenter,
     ruby_error_nomemory,
     ruby_error_sysstack,
+    ruby_error_sysstack_gc,
     ruby_error_stream_closed,
     ruby_special_error_count
 };

vm_insnhelper.c

@@ -57,7 +57,9 @@ void
 rb_threadptr_stack_overflow(rb_thread_t *th)
 {
     if (rb_during_gc()) {
-	rb_fatal("machine stack overflow while GC is running.");
+	th->ec.raised_flag = RAISED_STACKOVERFLOW;
+	th->ec.errinfo = th->vm->special_exceptions[ruby_error_sysstack_gc];
+	TH_JUMP_TAG(th, TAG_RAISE);
     }
 #ifdef USE_SIGALTSTACK
     threadptr_stack_overflow(th, TRUE);