On Tue, May 20, 2014 at 7:18 AM, Dmitry Antipov <dmanti...@yandex.ru> wrote: > > I'm trying to support -fsplit-stack in GNU Emacs. The most important problem > is that > GC uses conservative scanning of a C stack, so I need to iterate over stack > segments. > I'm doing this by using __splitstack_find, as described in > libgcc/generic-morestack.c; > but now I'm facing the weird issue with startup: > > Core was generated by `./temacs --batch --load loadup bootstrap'. > Program terminated with signal SIGSEGV, Segmentation fault. > #0 __morestack () at ../../../gcc-4.9.0/libgcc/config/i386/morestack.S:486 > 486 pushq %rax > (gdb) bt 10 > #0 __morestack () at ../../../gcc-4.9.0/libgcc/config/i386/morestack.S:486 > #1 0x00000000005f15df in __morestack () at > ../../../gcc-4.9.0/libgcc/config/i386/morestack.S:502 > #2 0x00000000005f15df in __morestack () at > ../../../gcc-4.9.0/libgcc/config/i386/morestack.S:502 > #3 0x00000000005f15df in __morestack () at > ../../../gcc-4.9.0/libgcc/config/i386/morestack.S:502
This is the call to __morestack_block_signals in morestack.S. It should only be possible if __morestack_block_signals or something it calls directly has a split stack. __morestack_block_signals has the no_split_stack attribute, meaning that it should never call __morestack. __morestack_block_signals only calls pthread_sigmark or sigprocmask, neither of which should be compiled with -fsplit-stack. So something has gone wrong, but I don't know what. I would recommend tracing the code instruction by instruction to see why __morestack_block_signals calls back into __morestack. Or, if that analysis is wrong, see what else is happening. I can advise but I don't have time to look at this in detail. Sorry. Ian
