Simple program segfaults when ThreadSanitizer is enabled

[Olivier Nicole]

Hi,

I tried out ThreadSanitizer on this simple program that spawns two threads: https://gist.github.com/OlivierNicole/20c6d58de1b773174a9bc093afb0cc09

The program runs fine but segfaults when instrumented by ThreadSanitizer:

    $ clang -Wall -Wextra -pedantic -std=c11 -pthread atomic_race.c
    $ ./a.out
    v = 10
    $ clang -Wall -Wextra -pedantic -std=c11 -pthread -fsanitize=thread atomic_race.c
    $ ./a.out
    ThreadSanitizer:DEADLYSIGNAL
    ==205049==ERROR: ThreadSanitizer: SEGV on unknown address 0x000000000000 (pc 0x000000490f8a bp 0x000000000000 sp 0x7f88234bf268 T205050)
    ==205049==The signal is caused by a WRITE memory access.
    ==205049==Hint: address points to the zero page.
    ThreadSanitizer:DEADLYSIGNAL
    ThreadSanitizer:DEADLYSIGNAL
    ThreadSanitizer: nested bug in the same thread, aborting.

Am I missing something?

Thanks,

Olivier

[Olivier Nicole]

I forgot to mention that I use clang version 7.1.0 on Linux.

[Dmitry Vyukov]

On Thu, 12 May 2022 at 14:25, Olivier Nicole <oli...@tarides.com> wrote:
>
> I forgot to mention that I use clang version 7.1.0 on Linux.

Hi Olivier,

clang 7 is too old, but this also reproduces with a fresh clang 15.
The root cause is that the C threading library not supported. I think
is equally broken for all sanitizers, they will crash or misbehave on
other programs (maybe during error reporting).

+Vitaly and asan/msan lists

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[Olivier Nicole]

Hi Dmitry,

Thanks for pointing this out. Are standard C++ threads supported?

[Dmitry Vyukov]

On Fri, 13 May 2022 at 14:24, Olivier Nicole <oli...@tarides.com> wrote:
>
> Hi Dmitry,
>
> Thanks for pointing this out. Are standard C++ threads supported?

It seems so:
https://github.com/llvm/llvm-project/blob/main/compiler-rt/test/tsan/compare_exchange.cpp#L66

Though I suspect it may depend on the implementation since sanitizers
only really intercept pthread_* calls.

> To view this discussion on the web visit https://groups.google.com/d/msgid/thread-sanitizer/bbe91ae1-12ee-416f-8d70-841b607a6baen%40googlegroups.com.

[Olivier Nicole]

FWIW, the program translated to C++ runs as expected with ThreadSanitizer and the glibc 2.33.