Jürg Billeter wrote: > It's not as easy as it sounds. As it's very likely that it's a GCC > optimization bug you can't really debug the compiled cfdisk as the > generated code is wrong. The stack after the SEGV is completely > destroyed, gdb doesn't help at all.
It seems as if you are able to reproduce the bug and have already investigated the issue in detail. You may well be correct about GCC optimization. I just did a quick test with -fverbose-asm of -O vs -O2 and here are the extra options that are enabled at -O2. While this is not guaranteed to show every GCC optimization pass, it should be pretty close. Presumably, it's one of these options that is causing the grief: -fcaller-saves -fcrossjumping -fcse-follow-jumps -fcse-skip-blocks -fdelete-null-pointer-checks -fexpensive-optimizations -fforce-mem -fgcse -foptimize-register-move -foptimize-sibling-calls -fpeephole2 -fregmove -freorder-blocks -freorder-functions -frerun-cse-after-loop -frerun-loop-opt -fschedule-insns2 -fstrength-reduce -fstrict-aliasing -fthread-jumps -ftree-pre -funit-at-a-time For anyone who can reproduce the crash, here is a suggested brute force approach to try and pinpoint the culprit: CFLAGS="-O" ./configure make -C fdisk <test cfdisk to see if it segfaults> make clean CFLAGS="-O -fcaller-saves" ./configure make -C fdisk <test cfdisk to see if it segfaults> make clean CFLAGS="-O -fcrossjumping" ./configure etc.. rinse, repeat well, you get the idea :-) T'is worth a shot methinks.. > What should really be done is trying to minimize the source code of > cfdisk as much as possible while keeping the segfault, so we'd have a > testcase to submit upstream resp. see whether it's already reported in > gcc's bugzilla. > > Maybe it wouldn't be that unwise to test with current 4.0 (or maybe also > 4.1) snapshot as it may already have been fixed. Will test that > afterwards and maybe try to create a testcase. Agreed. I wish I could reproduce this bug :( Regards Greg -- http://www.diy-linux.org/ -- http://linuxfromscratch.org/mailman/listinfo/lfs-dev FAQ: http://www.linuxfromscratch.org/faq/ Unsubscribe: See the above information page
