Re: _c_GSFFCallInvocation__load segfault

[Ildar Mulyukov]

   Helo, all, Adam!

Adam Fedor wrote:

> Ildar Mulyukov wrote:
>
> > This error occures in every program linked with gnustep-base.
> >
> > My configuration is Cygwin+GCC 3.0.1 self-built compiler (see 
> > http://www.cygwin.com/ml/cygwin/2001-10/msg00502.html). Due to test 
> > (see the reference above) I don't think it's compiler problem.
> >
> > I'll try to dig the problem but maybe you have any ideas? Any 
> > comments would be appreciated.
> > Thank you, Ildar.
> >
> > *** GDB log ***
> > Starting program: 
> > /d/Temp/doc/objc/test/./shared_debug_obj/ix86/cygwin/gnu-gnu-gnu/Test.exe 
> >
> >
> > Program received signal SIGSEGV, Segmentation fault.
> > _c_GSFFCallInvocation__load (self=0x4f51fc, _cmd=0xa019c98) at 
> > GSFFCallInvocation.m:454
>
>
> That's pretty odd. Are you using the libobjc library that comes with 
> gcc 3.0 or the gnustep-obj library? The gcc one doesn't properly 
> export some variables, but that would just not let you link the 
> program, I don't think it would cause it to crash.

This is actually not the problem of GCC's libobjc. In fact 
gnustep-libobjc does not export all needed symbols either (e.g. 
__objc_msg_forward). But this problem can be fixed very simply - just by 
adding symbols into libobjc.def file (again in

http://www.cygwin.com/ml/cygwin/2001-10/msg00502.html  
<http://www.cygwin.com/ml/cygwin/2001-10/msg00502.html>

). I tried also gcc-2.95.3+gnustep-libobjc pair with the same result. I 
found the real problem. Look at that simple code:
*****
extern void* (*__objc_msg_forward)(void*);

main() {
   void* p;
   p = __objc_msg_forward;
   __objc_msg_forward = 0; }
*****
when I do "gcc -g test.c -lobjc && ./a.exe" it coredumps with segfault. 
The problem occures when writing to __objc_msg_forward (the last line of 
the program). This is very strange as the example above works OK with a 
simple DLL exporting a variable like __objc_msg_forward. Probably I 
should ask about it at cygwin list...

Regards, Ildar.