[PATCH 1/3] Do not use __builtin_types_compatible_p in C++ mode (bug 21930)

[Joseph Myers]

On Tue, 15 Aug 2017, Gabriel F. T. Gomes wrote:

> The logic to define isinf for float128 depends on the availability of
> __builtin_types_compatible_p, which is only available in C mode,
> however, the conditionals do not check for C or C++ mode.  This lead to
> an error in libstdc++ configure, as reported by bug 21930.
> 
> This patch adds a conditional for C mode in the definition of isinf for
> float128.  No definition is provided in C++ mode, since libstdc++
> headers undefine isinf.

OK.

-- 
Joseph S. Myers
joseph@codesourcery.com