M_PI_2 missing from clang on Windows

Question

I make use of M_PI_2 from math.h in my source code.

This works fine for my Linux, OSX, iOS and Android builds.

When I use the clang compiler for Windows, I get:

use of undeclared identifier 'M_PI_2'

Why is there no M_PI_2 for my clang compiler on Windows? I compile with _POSIX_C_SOURCE=200112L

$ clang --version
clang version 6.0.1 (tags/RELEASE_601/final)
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:\Program Files\LLVM\bin

That's not in the C standard, and the Windows C standard library implementation thus probably doesn't bother to define it. — Shawn, Sep 16 '18 at 04:36
`M_PI_2` is not part of standard C. Consider writing code to the C standard and use `#define MY_PI_2 (3.1415926535897932384626433832795/2)` or `#define MY_PI_2 (asin(-1)/2)` or the like. — chux - Reinstate Monica, Sep 16 '18 at 04:57
Since when is Windows POSIX/UNIX compatible? Read the headline of the linked page. — too honest for this site, Sep 16 '18 at 10:54
@toohonestforthissite And yet, with _USE_MATH_DEFINES it behaves as required, thereby solving my problem. Valid problem. Valid solution. What's your problem? — Bram, Sep 16 '18 at 16:45

score -1 · Answer 1 · answered Sep 16 '18 at 05:09

-1

So, from ucrt/corecrt_math_defines.h I see that:

"Define _USE_MATH_DEFINES before including to expose these macro definitions..."

answered Sep 16 '18 at 05:09

Bram

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M_PI_2 missing from clang on Windows

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