Bug#798691: libc6-i686: sin() sometimes broken

[Christian Tacke <Christian.Tacke+debian.org@cosmokey.com>]

Package: libc6-i686
Version: 2.19-18+deb8u1
Severity: important

Hi,

I was trying to create a local backport of python-cffi onto
jessie/i386.

On a system with libc6-i686 installed, I get a failure in
the self test of the build:

>       assert library.sin(12.3) == math.sin(12.3)
E       assert 0.8444952930965295 == -0.26323179136580094

Uninstalling libc6-i686 lets the full build and tests run
through.

Something very related has already happened before:
https://www.sourceware.org/bugzilla/show_bug.cgi?id=16625

This suggests a compiler bug in gcc 4.8. But jessie is
compiled with 4.9, so it must be something a bit different.


Severity: important as giving wrong results to math
functions isn't something trivial, really and can affect
multiple unrelated components/packages.


Cheers

Christian

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