glibc-2.26 Implementation of signbit in math.h causes problem with C++ programs

[Florian Weimer]

* Andrew Paxie:

> Greetings.
>
> I read in
> https://sourceware.org/ml/libc-alpha/2017-08/msg00010.html
> that you wanted some feedback on which compilers can support
> glibc 2.26:
>
>   Older GCC versions and non-GNU compilers are still supported when
>   compiling programs that use the GNU C Library.  (We do not know exactly
>   how old, and some GNU extensions to C may be _de facto_ required.  If you
>   are interested in helping us make this statement less vague, please
>   contact libc-alpha@sourceware.org.)
>
>
> Here's a copy of a defect report I raised with Canonical,
> https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/1725869

Is this different from this bug we fixed?

  <https://sourceware.org/bugzilla/show_bug.cgi?id=22296>

It has been backported to the 2.26 stable branch as well.