Re: cmath vs. math.h vs isfinite

[Havard Eidnes <he%NetBSD.org@localhost>]

> Thomas Klausner <wiz%netbsd.org@localhost> writes:
> 
>> #include <cmath>
>> #include <math.h>
>
> I am guessing there is a bug, but I have been running into a
> perhaps-related issue.  This note is from memory so may be slightly off.
>
> In C++, if you include <cmath>, and then want to use e.g. abs, the
> standards say that you should write std::abs().  But they allow
> compilers to make std::abs() available as just abs(), and some code does
> that.  I fairly frequently find instances of this, and submit upstream
> bug reports.  I have found that almost always, maybe always, upstreams
> fix this (or perhaps, do not say I'm wrong, don't remember if any
> nonresponsive).
>
> I think what you are seeing is different, which is that things declared
> in C for math.h are omitted.

I've been in this area before, but ran out of energy explaining
myself, ref.

  https://github.com/pandas-dev/pandas/pull/51049

> A further standards question: Why is it ok to include math.h in C++
> without extern "C"?

A valid question.

- Håvard