Segmentation fault on sclass with block

[ksss]

t.rb

module A
  def self.sclass_with_block
    class << self
      yield
    end
  end
end

p A.sclass_with_block { 123 }

$ ruby t.rb
123

$ mruby t.rb
[1]    32880 segmentation fault  mruby t.rb

This behavior was defined on ruby/spec.

https://github.com/ruby/spec/blob/d05fabfe0ba3774710d912d2802d6d235c1ed8ae/language/class_spec.rb#L290

The reasons is that outer class is recursive.

lldb backtrace.

$ lldb mruby
(lldb) run t.rb
Process 33414 launched: 'bin/mruby' (x86_64)
Process 33414 stopped
* thread #1: tid = 0x4b3514, 0x00000001000363f8 mruby`sym_validate_len(mrb=<unavailable>, len=<unavailable>) + 8 at symbol.c:41, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=2, address=0x7fff5f3ffff8)
    frame #0: 0x00000001000363f8 mruby`sym_validate_len(mrb=<unavailable>, len=<unavailable>) + 8 at symbol.c:41
   38
   39   static void
   40   sym_validate_len(mrb_state *mrb, size_t len)
-> 41   {
   42     if (len >= RITE_LV_NULL_MARK) {
   43       mrb_raise(mrb, E_ARGUMENT_ERROR, "symbol length too long");
   44     }
(lldb) bt
...
    frame #32748: 0x000000010000b82a mruby`mrb_class_path(mrb=0x0000000100202ad0, c=0x00000001008063e0) + 218 at class.c:1512
    frame #32749: 0x000000010000b82a mruby`mrb_class_path(mrb=0x0000000100202ad0, c=0x00000001008063e0) + 218 at class.c:1512
    frame #32750: 0x000000010000b82a mruby`mrb_class_path(mrb=0x0000000100202ad0, c=0x00000001008063e0) + 218 at class.c:1512
    frame #32751: 0x000000010000b82a mruby`mrb_class_path(mrb=0x0000000100202ad0, c=0x00000001008063e0) + 218 at class.c:1512
    frame #32752: 0x000000010000b82a mruby`mrb_class_path(mrb=0x0000000100202ad0, c=0x00000001008063e0) + 218 at class.c:1512
    frame #32753: 0x000000010000b82a mruby`mrb_class_path(mrb=0x0000000100202ad0, c=0x00000001008063e0) + 218 at class.c:1512
    frame #32754: 0x000000010000b82a mruby`mrb_class_path(mrb=0x0000000100202ad0, c=0x00000001008063e0) + 218 at class.c:1512
    frame #32755: 0x000000010000b82a mruby`mrb_class_path(mrb=0x0000000100202ad0, c=0x00000001008063e0) + 218 at class.c:1512
    frame #32756: 0x000000010000b82a mruby`mrb_class_path(mrb=0x0000000100202ad0, c=0x00000001008063e0) + 218 at class.c:1512
    frame #32757: 0x000000010000ba3d mruby`mrb_class_name(mrb=0x0000000100202ad0, c=0x00000001008063e0) + 29 at class.c:1549
    frame #32758: 0x00000001000061ea mruby`output_backtrace_i(mrb=0x0000000100202ad0, loc_raw=0x00007fff5fbff3a0, data=0x00007fff5fbff408) + 106 at backtrace.c:170
    frame #32759: 0x0000000100005db1 mruby`each_backtrace(mrb=0x0000000100202ad0, ciidx=2, pc0=0x00000001002348f0, func=(mruby`output_backtrace_i at backtrace.c:161), data=0x00007fff5fbff408) + 529 at backtrace.c:150
    frame #32760: 0x00000001000059fc mruby`output_backtrace(mrb=0x0000000100202ad0, ciidx=2, pc0=0x00000001002348f0, func=(mruby`print_backtrace_i at backtrace.c:47), data=0x00007fff5fbff4f8) + 76 at backtrace.c:181
    frame #32761: 0x000000010000554c mruby`exc_output_backtrace(mrb=0x0000000100202ad0, exc=0x0000000100805c30, func=(mruby`print_backtrace_i at backtrace.c:47), stream=0x00007fff5fbff4f8) + 252 at backtrace.c:197
    frame #32762: 0x000000010000518b mruby`mrb_print_backtrace(mrb=0x0000000100202ad0) + 315 at backtrace.c:278
    frame #32763: 0x0000000100028935 mruby`mrb_print_error(mrb=0x0000000100202ad0) + 21 at print.c:33
    frame #32764: 0x00000001000012b9 mruby`main(argc=2, argv=0x00007fff5fbff6f0) + 1081 at mruby.c:238
    frame #32765: 0x00007fff9b92e5ad libdyld.dylib`start + 1

Outer class was set on here.

mruby/src/class.c

Lines 1135 to 1136 in 77d004e

	mrb_obj_iv_set(mrb, (struct RObject*)obj->c, mrb_intern_lit(mrb, "__outer__"),
	mrb_obj_value(mrb->c->ci->target_class));

When obj->c == mrb->c->ci->target_class,

Recursive calling happened on the below line.

mruby/src/class.c

Line 1512 in 77d004e

mrb_value base = mrb_class_path(mrb, outer);

---

I applied this patch.
It didn't raise segv.
But behavior was different with CRuby.

diff --git a/src/class.c b/src/class.c
index 47a6c84..40faffb 100644
--- a/src/class.c
+++ b/src/class.c
@@ -1131,7 +1131,7 @@ mrb_singleton_class(mrb_state *mrb, mrb_value v)
   }
   obj = mrb_basic_ptr(v);
   prepare_singleton_class(mrb, obj);
-  if (mrb->c && mrb->c->ci && mrb->c->ci->target_class) {
+  if (mrb->c && mrb->c->ci && mrb->c->ci->target_class && obj->c != mrb->c->ci->target_class) {
     mrb_obj_iv_set(mrb, (struct RObject*)obj->c, mrb_intern_lit(mrb, "__outer__"),
                    mrb_obj_value(mrb->c->ci->target_class));
   }

$ mruby t.rb
trace:
    [2] t.rb:6
    [1] t.rb:5:in A#sclass_with_block
    [0] t.rb:11
LocalJumpError: unexpected yield

https://github.com/mruby/mruby/blame/77d004e8352dab0bcb0c9bd6826f20a5e0185e3e/src/vm.c#L1737