Ocassionally line number in stacktrace is 0

[alex]

I'm not sure where this bug exists, it might be a bug in ASAN or the symbolizer, filing here as a first step :-)

If you look at https://oss-fuzz.com/v2/testcase-detail/5638304557957120?noredirect=1 at frame #5 you can see it points to line 0. I'm not sure what the cause might be, none of the potential locations are in macros or anything else that I might expect to cause problems.

[kcc]

These are usually bugs in the compiler-generated dwarf or (less frequently) in the symbolizer.
Unless this is something very frequent and very annoying I'd just ignore it.
Bugs like this are periodically fixed, and getting the reproducer from imagemagick will require disproportionately large work.

[alex]

It's definitely not ruining my life or anything :-) Sounds like the best thing to do is just hope LLVM fixes whatever the bug is.

[kcc]

Yep. As usual, if you have a smaller repro the bug is more likely to be fixed.

[alex]

Indeed.

[alex]

Is there a good way to attempt to test whether an attempted repro is effected without actually triggering an ASAN failure?

[kcc]

just use addr2line and llbm-symbolizer on the binary with the affected PC.
If addr2line also shows bogus value, it's likely a bug in emitted dwarf.
If llvm-symbolizer shows the bogus value and addr2line shows a good one, most likely the LLVM dwarf reader is wrong.
(You can also dump dwarf with elfdump and some such, but I never remember the incantations)

[alex]

thanks

…

On Sat, Feb 17, 2018 at 4:26 PM, Kostya Serebryany ***@***.*** > wrote: just use addr2line and llbm-symbolizer on the binary with the affected PC. If addr2line also shows bogus value, it's likely a bug in emitted dwarf. If llvm-symbolizer shows the bogus value and addr2line shows a good one, most likely the LLVM dwarf reader is wrong. (You can also dump dwarf with elfdump and some such, but I never remember the incantations) — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1173 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAADBI2j3RdlEddR_gzK46RLFugkxLvRks5tV0PzgaJpZM4SJVi_> .

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