Bug#1086489: xsimd: autopkgtest is failing on arm64

[Emilio Pozuelo Monfort]

On Fri, 22 Nov 2024 23:55:29 +0100 Drew Parsons <dparsons at debian.org> wrote:
> Control: forwarded 1086489 https://github.com/xtensor-stack/xsimd/issues/1066
> 
> Emilio's verbose log shows
> 
> 2885s 1: /tmp/autopkgtest-lxc.8mniqst8/downtmp/build.OlH/src/test/test_xsimd_api.cpp:631: ERROR: CHECK_EQ( extract(xsimd::lgamma(T(val))), std::lgamma(val) ) is NOT correct!
> 2885s 1:   values: CHECK_EQ( -nan, 0 )
> 
> 
> i.e. the problem is that lgamma is returning -nan when built with clang 19 on arm64.
> 
> Not clear from the error whether the fault lies with xsimd or with clang.
> Bug filed with xsimd upstream.

There's a suggestion in the bug report to fix an uninitialized read in lgamma, 
which could be causing the bug. Can you upload that, or else I'm happy to push 
it if you ack it.

If that fails, we could switch xsimd to LLVM 18 or 17, but hopefully not 16 as I 
want to get rid of that.

Cheers,
Emilio