I investigated as to why my grub wouldn't install when it looked like the compile was OK. Now emerging GDB and also attempting to re-emerge with different CFLAGS (just -O2, removing -march=native).
Taro build-pc # ./grub-mkimage --help
Usage: grub-mkimage [OPTION...] [OPTION]... [MODULES]
Make a bootable image of GRUB.
-c, --config=FILE embed FILE as an early config
Segmentation fault (core dumped)
What's weird is it should just be printing some output. That shouldn't crash it unless there is a major bug.
Well ... it installed. Is there some way to tell portage to change CFLAGS for a certain program? Is there an /etc/portage/package.cflags? I know the ebuilds can do it, but the ebuild isn't filtering out -march=native, which is definately breaking grub (like a bug somewhere). I'm gonna compile the broken one, just so I can gdb it.
Program received signal SIGSEGV, Segmentation fault.
0x000000000041459a in memset ()
(gdb) bt
#0 0x000000000041459a in memset ()
#1 0x0000000000414672 in memset ()
#2 0x0000000000414672 in memset ()
#3 0x0000000000414672 in memset ()
#4 0x0000000000414672 in memset ()
This repeats until the stack overflows ... at least 10000 times. Weird eh?
It looks like even gcc's own test suite caches the bug and yet they released it anyway :/ Only bites with -O3 when doing something like that looks like a memcopy. GCC will optimize by calling the library routine which can result in an infinite loop. In which case you can fix the source with:
Or just tweak the ebuild to add "-fno-tree-loop-distribute-patterns" to the CFLAGS in the ebuild and be done with it.
Yup - this fixes it! Off to file a bug. (and keeping that -fno-tree-loop-... in my global CFLAGS, who knows what other apps will silently fail - I should probably recompile EVERYTHING).
Question
uudruid74
I investigated as to why my grub wouldn't install when it looked like the compile was OK. Now emerging GDB and also attempting to re-emerge with different CFLAGS (just -O2, removing -march=native).
What's weird is it should just be printing some output. That shouldn't crash it unless there is a major bug.
Well ... it installed. Is there some way to tell portage to change CFLAGS for a certain program? Is there an /etc/portage/package.cflags? I know the ebuilds can do it, but the ebuild isn't filtering out -march=native, which is definately breaking grub (like a bug somewhere). I'm gonna compile the broken one, just so I can gdb it.
This repeats until the stack overflows ... at least 10000 times. Weird eh?
I think its related to this GCC bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56888
It looks like even gcc's own test suite caches the bug and yet they released it anyway :/ Only bites with -O3 when doing something like that looks like a memcopy. GCC will optimize by calling the library routine which can result in an infinite loop. In which case you can fix the source with:
#pragma GCC optimize ("no-tree-loop-distribute-patterns")
Or just tweak the ebuild to add "-fno-tree-loop-distribute-patterns" to the CFLAGS in the ebuild and be done with it.
Yup - this fixes it! Off to file a bug. (and keeping that -fno-tree-loop-... in my global CFLAGS, who knows what other apps will silently fail - I should probably recompile EVERYTHING).
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