bug#13611: SEGV during SMOB GC

[Mike Gran]

> From: Ludovic Courtès <address@hidden>

> Is there any chance that you’re using a GC 7.3 pre-release?

Using gc-7.2b-2.fc17.i686
on Linux 3.6.10-2.fc17.i686 #1 SMP 

> There was a similar report on IRC, and the fix appears to be:

It does fix my SEGV

> (Note that on 2.0 SMOB mark procedures are unnecessary.)

Cool.  Let's yank it from the manual.  Case closed.

Yet...

For what it is worth, I decided to get som statistics on how
often smob_mark is called from a thread with scm_i_current_thread
== NULL vs how often it is called from a thread where it is 
not null.

I wrote the attached patch, and then, using the same little
library as in my initial report, I ran

 (use-modules (smobbug))
 ;; Create a SMOB type
 (handlesmob-init)
 (for-each (lambda (x) (gc))
       (iota 1000))
 (gc-smob-mark-report)

This returned

 Count of GC SMOB marks from null thread: 176
 Count of GC SMOB marks from current thread: 825

Is that expected that GC is sometimes called from a 
thread where scm_i_current_thread is null and sometimes
called from a thread where scm_i_current_thread is
not null?

-Mike

smob_gc_mark_report.patch
Description: Text Data