[cfe-users] Clang9 UBSan and GMP

David Blaikie via cfe-users cfe-users at lists.llvm.org
Wed Oct 30 14:17:22 PDT 2019

I ran the test & understand it a bit better now - so the abort is part of
the code, when the test fails, the test harness uses abort to fail.

So this isn't "clang causes abort" (it didn't select a bad instruction,
etc) this is "clang causes test failure" - this could be any number of
things in terms of compiler optimizations due to overly dependent code (or
due to miscompiles, to be sure). It's possible the test relies on specific
numeric results that the C++ programming language doesn't guarantee (either
overly high precision, or overly low precision - C++ allows extra precision
in computations which can break numerical code that's relying on certain
precision, for instance).

So, yeah, really hard to say where the fault lies without further

On Fri, Oct 25, 2019 at 4:13 PM Hans Ã…berg <haberg-1 at telia.com> wrote:

> The GMP developers felt it was a compiler bug, so I think I will leave it
> at that. But thanks for the tips.
> > On 26 Oct 2019, at 00:32, David Blaikie <dblaikie at gmail.com> wrote:
> >
> > UBSan doesn't catch everything - you could also try ASan and/or
> valgrind, etc. (MSan if you want, but that's a bit fussier/more work to use)
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