mrb_string_value_cstr crashes if not given a string

[jbreeden]

mrb_string_value_cstr does horrible things if given an argument that isn't actually a string (well, it tends to crash, anyway). That's all fine and well, since in C you should know what you're doing with your pointers. However, mrb_string_value_ptr avoids this by calling mrb_str_to_str on its argument. I'm just wondering if there's a reason that they behave differently. (Until now, I thought the _cstr version just stopped at the first null character, and _ptr was more suited to arbitrary char buffers. It wasn't clear to me that one is more type sensitive.)

I didn't see any issues/discussions on this yet. Maybe I'm the only one that's confused... O_o

[cremno]

You should create a PR. I agree that mrb_str_to_str() has to be called. I think most mruby users call mrb_str_to_cstr() instead which is very strict (just MRB_TT_STRING) and (or rather but?) creates a copy. Also this function is only used once in mruby and there it's preceded by a check. That's probably why nobody has found this bug before.

However there's something else: mrb_str_to_str() does much more than rb_str_to_str(). Is this intended, @matz?

mruby/src/string.c

Lines 628 to 641 in e344c6a

	MRB_API mrb_value
	mrb_str_to_str(mrb_state *mrb, mrb_value str)
	{
	mrb_value s;
	if (!mrb_string_p(str)) {
	s = mrb_check_convert_type(mrb, str, MRB_TT_STRING, "String", "to_str");
	if (mrb_nil_p(s)) {
	s = mrb_convert_type(mrb, str, MRB_TT_STRING, "String", "to_s");
	}
	return s;
	}
	return str;
	}

https://github.com/ruby/ruby/blob/a02a3f46496210ca401fd74585993c8754cbe91c/string.c#L1087-L1091

[jbreeden]

Sounds good. I'm heading to work, I'll make the PR when I get back.