Re: disturbing g++ 971031 results. defer-pop to blame?

[Andreas Schwab <schwab@issan.informatik.uni-dortmund.de>]

Jeffrey A Law <law@cygnus.com> writes:

|>   In message < 19971103011246.03918@dgii.com >you write:
|>   > GDB that I built from 4.14-95q4 (i486-unknown-sco3.2v5.0.0elf) handles 
|>   > the binaries in question just fine.   GDB 4.16 built from virgin FSF 
|>   > sources isn't useful on my ELF binaries.   I'll chase this later...
|> Sounds wise :-)

|>   > Program received signal SIGSEGV, Segmentation fault.
|>   > 0x8059187 in .fini ()
|> Now we're getting somewhere...

|>   > If I look at the tail end of the object, the reason for our
|>   > crash is more apparent:
|>   > 
|>   > Disassembly of section .fini:
|>   > 
|>   > 0805917c <_fini>:
|>   >  805917c:       e8 c7 f9 fe ff  call   8048b48 <__do_global_dtors_aux>
|>   >  8059181:       90              nop
|>   >  8059182:       90              nop
|>   >  8059183:       90              nop
|>   > 
|>   > 08059184 <.fini>:
|>   >  8059184:       4c              decl   %esp
|>   >  8059185:       cd 04           int    $0x4
|>   >  8059187:       08 c2           orb    %al,%dl
|>   > 
|>   > 08059188 <.fini>:
|>   >  8059188:       c2 00 00        ret    $0x0
|>   >  805918b:       90              nop
|> Hmmmm.
|> If you look at fini_dummy in crtstuff.c you'll see how this happened:

|> static void
|> fini_dummy ()
|> {
|>   asm (FINI_SECTION_ASM_OP);
|>   __do_global_dtors_aux ();
|> #ifdef FORCE_FINI_SECTION_ALIGN
|>   FORCE_FINI_SECTION_ALIGN;
|> #endif
|>   asm (TEXT_SECTION_ASM_OP);
|> }

|> We switch into the FINI section, emit the call, align the section,
|> then switch out -- without ever emitting a return.

This is ok, the final return is added by crtn.o which is linked in this
example at 08059188.  The invalid instructions between 08059184 and
08059188 are coming from a different object.

-- 
Andreas Schwab                                      "And now for something
schwab@issan.informatik.uni-dortmund.de              completely different"
schwab@gnu.org