SegFault in mwrap 2.1 on Ruby 2.4.7

SegFault in mwrap 2.1 on Ruby 2.4.7

[alex]

Hi,

I'm getting segmentation fault with mwrap 2.1 & Ruby 2.4.7.

I'm not a C developer but I'll be happy to try and help debug this.

So far this is what I've gathered.

Reproduction steps:

1. Run: mwrap ruby -e ''

Backtrace:

#0  0x00007ffff7bd34d2 in has_ec_p () at mwrap.c:216
#1  0x00007ffff7bd3c23 in update_stats_rcu_lock (size=5, caller=140737336167861) at mwrap.c:426
#2  0x00007ffff7bd48d4 in malloc (size=5) at mwrap.c:721
#3  0x00007ffff6edcdb5 in _nl_normalize_codeset () from /lib64/libc.so.6
#4  0x00007ffff6ed710f in _nl_load_locale_from_archive () from /lib64/libc.so.6
#5  0x00007ffff6ed630e in _nl_find_locale () from /lib64/libc.so.6
#6  0x00007ffff6ed5ad3 in setlocale () from /lib64/libc.so.6
#7  0x0000555555578f8a in main ()

Source for reference:

211	 * to have a native thread but no EC during the early and late
212	 * (teardown) phases of the Ruby process
213	 */
214	static int has_ec_p(void)
215	{
216		return (ruby_thread_has_gvl_p() && ruby_current_vm_ptr &&
217			ruby_current_execution_context_ptr);
218	}
219
220	struct acc {

--
Alex

SegFault in mwrap 2.1 on Ruby 2.4.7

[alex]

Apparently, Ruby internals have changed between 2.4 and 2.5.

Specifically the following definitions are not correct for Ruby 2.4:

mwrap.c:

28 extern void * __attribute__((weak)) ruby_current_execution_context_ptr;
29 extern void * __attribute__((weak)) ruby_current_vm_ptr; /* for rb_gc_count */

They can be found in ruby/vm_core.h in Ruby 2.5+ but not in Ruby 2.4. That said,
I don't know what the right definitions are for Ruby 2.4 or if it's possible
to make mwrap copatible with Ruby 2.4.

--
Alex

Re: SegFault in mwrap 2.1 on Ruby 2.4.7

[Eric Wong]

alex@pointless.one wrote:
> They can be found in ruby/vm_core.h in Ruby 2.5+ but not in Ruby 2.4. That said,
> I don't know what the right definitions are for Ruby 2.4 or if it's possible
> to make mwrap copatible with Ruby 2.4.

Right, mwrap requires Ruby 2.6 or later.  The README says:

| It does not require recompiling or rebuilding Ruby, but only
| supports Ruby trunk (2.6.0dev+) on a few platforms: