Re: [Fxruby-users] segfault with FXTreeList in Ruby 1.8.0

[Joel V. <vj...@PA...>]

Lyle Johnson wrote:
> Joel VanderWerf wrote:
> 
>> Has anyone seen this? I'm getting a segfault in a finalizer for a 
>> FXTreeList. It happens in 1.8.0, but not 1.7.3.
>>
>> Here's the backtrace:
>>
>> Program received signal SIGSEGV, Segmentation fault.
>> 0x0805947b in rb_longjmp (tag=6, mesg=0) at eval.c:3924
>> 3924        JUMP_TAG(tag);
>> (gdb) bt
>> #0  0x0805947b in rb_longjmp (tag=6, mesg=0) at eval.c:3924
>> #1  0x080594f1 in rb_exc_raise (mesg=1087374512) at eval.c:3931
>> #2  0x080bfe08 in rb_raise (exc=1075655904,
>>     fmt=0x80dafe0 "wrong argument type %s (expected %s)") at error.c:694
>> #3  0x080befb4 in rb_check_type (x=0, t=135298648) at error.c:254
>> #4  0x40339825 in SWIG_ConvertPtr (obj=1087378452, ptr=0xbfffede0,
>>     ty=0x406d0580, flags=1) at librb.c:403
>> #5  0x405a00c2 in _wrap_FXTreeItem_setFocus (argc=1, argv=0xbfffeff0,
>>     self=1087378452) at treelist_wrap.cpp:685
> 
> 
> <snip>
> 
> I snipped it here because this part alone has some questionable stuff 
> going on. At frame #5, we see that _wrap_FXTreeItem_setFocus() called 
> SWIG_ConvertPtr(), to extract the pointer to the C++ FXTreeItem object 
> from the Ruby FXTreeItem instance. In both frames 4 and 5, the Ruby 
> instance has a VALUE of 1087378452. But then by the time we get to the 
> call to rb_check_type() at frame #3, this value has become zero (x=0).
> 
> Are you running under Linux? Have you tried to valgrind it yet?

Linux Mandrake 9.1. I've never learned to use valgrind (maybe this would 
be a good excuse to do so :))

As you point out, this is very strange. The pc at frame #4 is inside the 
DataGetStruct(obj, ...) macro, which calls rb_check_type() with obj as 
the first arg. But at that point the value has been clobbered somehow.

I'll give valgrind a shot...