# Odd random segfaults in 1.9.2dev with gem method

**URL:** <https://www.ruby-forum.com/t/odd-random-segfaults-in-1-9-2dev-with-gem-method/174915>\
**Category:** Ruby\
**Created:** [September 4, 2009, 12:23am UTC](https://www.ruby-forum.com/t/odd-random-segfaults-in-1-9-2dev-with-gem-method/174915 "2009-09-04T00:23:14Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Nikolai\_L](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/2acd7d/32.png) [@Nikolai\_L](https://www.ruby-forum.com/u/Nikolai_L)\
**Post date:** [September 4, 2009, 12:23am UTC](https://www.ruby-forum.com/t/odd-random-segfaults-in-1-9-2dev-with-gem-method/174915/1 "2009-09-04T00:23:14Z")

</div>

Got some segfault errors when trying to run rake test for rails.

Minimal code example to reproduce is: ruby -e ‘gem “rake”’

the odd thing is that these segfaults are not 100% reproducible,  
sometimes it works as expected:

-----8\<----------  
$ ruby -e ‘gem “rake”’  
internal:gem\_prelude:187:in `push_gem_version_on_load_path': Could not find RubyGem rake (>= 0) (Gem::LoadError) from /home/nlugovoi/lib/ruby/1.9.1/rubygems/defaults.rb:0:in`rescue in default\_exec\_format’  
from -e:1:in `’  
-----8\<----------

But sometimes it just fails:

-----8\<----------  
$ ruby -e ‘gem “rake”’  
/home/nlugovoi/lib/ruby/1.9.1/rubygems.rb:1093: [BUG] Segmentation fault  
ruby 1.9.2dev (2009-09-04 trunk 24743) [i686-linux]

– control frame ----------  
c:0012 p:---- s:0043 b:0043 l:000042 d:000042 CFUNC :require  
c:0011 p:0209 s:0039 b:0039 l:000038 d:000038 TOP  
/home/nlugovoi/lib/ruby/1.9.1/rubygems.rb:1093  
c:0010 p:---- s:0036 b:0036 l:000035 d:000035 FINISH  
c:0009 p:---- s:0034 b:0034 l:000033 d:000033 CFUNC :require  
c:0008 p:0092 s:0030 b:0030 l:000029 d:000029 METHOD  
internal:gem\_prelude:159  
c:0007 p:0017 s:0027 b:0027 l:000026 d:000026 METHOD  
internal:gem\_prelude:279  
c:0006 p:---- s:0023 b:0023 l:000022 d:000022 FINISH  
c:0005 p:0043 s:0021 b:0020 l:000019 d:000019 METHOD  
internal:gem\_prelude:187  
Segmentation fault  
-----8\<----------

From gdb I get:

-----8\<----------  
#0 0x0813a387 in vm\_backtrace\_push (arg=0xbfffa0ec, file=0,  
line\_no=0, name=0) at vm.c:755  
#1 0x0813a2db in vm\_backtrace\_each (th=0x81faa98, lev=-2,  
iter=0x813a363 \<vm\_backtrace\_push\>, arg=0xbfffa0ec) at vm.c:733  
#2 0x0813a44c in vm\_backtrace (th=0x81faa98, lev=-1) at vm.c:768  
#3 0x08138ac7 in rb\_make\_backtrace () at vm\_eval.c:1426  
#4 0x0805b8ac in rb\_longjmp (tag=6, mesg=140818900) at eval.c:363  
#5 0x0805bb5e in rb\_exc\_raise (mesg=140818900) at eval.c:419  
#6 0x0816d319 in rb\_raise (exc=136482940, fmt=0x81a3676 “no such file  
to load – %s”) at error.c:1132  
#7 0x0816f580 in load\_failed (fname=140824860) at load.c:532

754 bt = rb\_enc\_sprintf(rb\_enc\_compatible(file, name), “%s:%d:in  
`%s’”,  
755 RSTRING\_PTR(file), line\_no,  
RSTRING\_PTR(name));  
(gdb) up  
#1 0x0813a2db in vm\_backtrace\_each (th=0x81faa98, lev=-2,  
iter=0x813a363 \<vm\_backtrace\_push\>, arg=0xbfffa0ec) at vm.c:733  
733 if ((\*iter)(arg, file, line\_no, iseq-\>name))  
break;  
(gdb) l  
728 if (cfp-\>pc != 0) {  
729 rb\_iseq\_t \*iseq = cfp-\>iseq;  
730  
731 line\_no = rb\_vm\_get\_sourceline(cfp);  
732 file = iseq-\>filename;  
733 if ((\*iter)(arg, file, line\_no, iseq-\>name))  
break;  
734 }  
-----8\<----------

My theory is that when method Kernel#gem, originally defined in  
gem\_prelude, is redefined/discarded in rubygems.rb, then original  
iseq for method becomes orphaned and is freed by garbage collector.  
But it is still referenced from control frame, so segfault.

I tried quick&dirty patch to explicitly mark iseq objects, not sure  
if it is correct way:  
-----8\<----------  
— a/vm.c  
+++ b/vm.c  
@@ -1415,7 +1415,21 @@ static int  
vm\_mark\_each\_thread\_func(st\_data\_t key, st\_data\_t value, st\_data\_t  
dummy)  
{  
VALUE thval = (VALUE)key;

- rb\_thread\_t \*th;
- rb\_control\_frame\_t \*cfp;
- 
- GetThreadPtr(thval, th);
- 
- cfp = th-\>cfp;
- while (!RUBY\_VM\_CONTROL\_FRAME\_STACK\_OVERFLOW\_P(th, cfp)) {
- 

```
  if (RUBY_VM_NORMAL_ISEQ_P(cfp->iseq)) {

```

- 

```
          rb_gc_mark(cfp->iseq->self);

```

- 

```
  }

```

- 

```
  cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);

```

- }
- rb\_gc\_mark(thval);
- return ST\_CONTINUE;  
}  
-----8\<----------  
and that seemed to eliminate such segfaults

Any other explanations or fixes?

---

<div class="post-metadata">

**Author:** ![Nikolai\_L](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/2acd7d/32.png) [@Nikolai\_L](https://www.ruby-forum.com/u/Nikolai_L)\
**Post date:** [September 4, 2009, 1:49am UTC](https://www.ruby-forum.com/t/odd-random-segfaults-in-1-9-2dev-with-gem-method/174915/2 "2009-09-04T01:49:18Z")

</div>

yes, i also get this error

minimum example

gem(‘twitter4r’, ‘\>=0.2.0’)

gives me

/usr/local/lib/ruby/1.9.1/rubygems.rb:1093: [BUG] Segmentation fault  
ruby 1.9.2dev (2009-09-03 trunk 24741) [i686-linux]

– control frame ----------  
c:0010 p:---- s:0036 b:0036 l:000035 d:000035 CFUNC :require  
c:0009 p:0209 s:0032 b:0032 l:000031 d:000031 TOP  
/usr/local/lib/ruby/1.9.1/rubygems.rb:1093  
c:0008 p:---- s:0029 b:0029 l:000028 d:000028 FINISH  
c:0007 p:---- s:0027 b:0027 l:000026 d:000026 CFUNC :require  
c:0006 p:0092 s:0023 b:0023 l:000022 d:000022 METHOD  
internal:gem\_prelude:159  
c:0005 p:0314 s:0020 b:0020 l:000019 d:000019 METHOD  
internal:gem\_prelude:213  
Segmentation fault