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Re: Strange C++ function pointer test


On 6 January 2016 at 21:05, Jonathan Wakely wrote:
> I have been meaning to try solving it in libstdc++ with a new <math.h>
> that includes the libc one and extends it, to see how well that works.
> I haven't had time to try that, so it would be premature to ask for
> changes to be made to glibc when I don't know if they are necessary or
> would even be the best solution.

I have a working patch (to be posted later today) which fixes this
issue, and LWG 2294.

However, because my patch means that <math.h> always includes <cmath>
it makes it much easier to hit PR48892 (aka PR60407 aka PR68984). I
have a workaround for that, which is fragile and ugly. A better
solution would be for glibc's mathcalls.h to suppress the non-generic
Unix98 isnan and isinf functions when included from C++, as Joseph
suggested at https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54130#c14

Libstdc++ can #undef isinf and #undef isnan to remove the C99 macros,
but it can't undefine functions, we'd need to use fixincludes for
that. Maybe it's time to address the isinf/isnan issue properly.


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