http://bugzilla.novell.com/show_bug.cgi?id=1040589
http://bugzilla.novell.com/show_bug.cgi?id=1040589#c2
--- Comment #2 from Richard Biener
In https://build.opensuse.org/project/prjconf/openSUSE:Factory we have %do_profiling 1
and because of that in our bash.spec we enable gcc's 'profile feedback directed optimizations'
but that causes the jobs.o and resulting bash binary to differ between builds, even when running on the same build host.
And because of that, build-compare always thinks there is a change and triggers a re-publish and rebuild of depending packages
We also have such binary diffs in gcc6 and gcc6.spec calls a make profiledbootstrap
The do_profiling macro is used in bash gzip hello python3-base python-base sed xz
and in http://rb.zq1.de/compare.factory-20170523/bash-compare.out http://rb.zq1.de/compare.factory-20170523/gcc6-compare.out http://rb.zq1.de/compare.factory-20170523/gzip-compare.out http://rb.zq1.de/compare.factory-20170523/python-base-compare.out http://rb.zq1.de/compare.factory-20170523/python3-base-compare.out
we have strange diffs in assembler that I could not trace down to other sources of non-determinism until today.
Is the buildroot 1:1 the same and then you get different code?
Diffs did go away when building without profiling (it was harder to disable for gcc6 and bash though)
Do the profiles just count invocations of functions or do they depend on the type and speed of the system?
Just counting. Inconsistencies can pop up when you run the instrumented binaries in parallel (gcov uses file locking but still we see that happen).
In the first case, it should be possible to fix the profiling runs to be deterministic, but for that it would be useful to be able to see the differences between runs. How could I diff gcc's .gcda files?
There is gcov-dump (might need to pick it up from devel:gcc gcc packages). -- You are receiving this mail because: You are on the CC list for the bug.