Should We Move To Thread Sanitizer?

[Joe Best-Rotheray]

As the title suggests, I recently learned that thread sanitizer is also a data race detector, by the same author as Relacy! Should we all switch to using thread sanitizer instead of Relacy?

Cheers

Joe

[Ronald Landheer-Cieslak]

Thread sanitizer is part of clang (and more or less works in gcc), doesn't "promise anything" for C++ and has a different model than relacy. I see them as complimentary approaches.

Should you use thread sanitizer? Sure!

Should you stop using relacy? I wouldn't. (Not yet)

rlc

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[Dmitry Vyukov]

What Ronald said.
Relacy is intended for rigorous verification of synchronization
algorithms. It checks lots of different thread interleavings,
precisely models and relaxes memory model. But it can't handle any
real application.
ThreadSanitizer does not check multiple executions, does not relax
memory model and does somewhat coarser modelling. But on the other
hand it can handle applications of almost arbitrary size (e.g. we are
testing Chromium with ThreadSanitizer).

[Joe Best-Rotheray]

Cool, so am I right in thinking that Relacy is able to kind of "emulate" non-x86 processors? Some of the bugs that Relacy has found seem to be problems that I wouldn't expect to have seen on x86. If so, that's insanely useful, as I'm never going to bother testing my code on Arm or PPC!

[Dmitry Vyukov]

Right.
But note that if you program in C/C++ (rather than in x86
assembly/machine codes), the fact that the underlying hardware is x86
is irrelevant. C/C++ have own memory model and you need to program
against it. The problem is that _compiler_ can do all kinds of memory
reorderings, can split word stores, etc. See (especially the second
example with double):
https://github.com/google/sanitizers/wiki/ThreadSanitizerAboutRaces#volatile

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