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Date: Fri, 8 Jan 2010 12:09:21 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: gcc4: OpenMP vs. <math.h>
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On Jan  8 01:40, Yaakov S wrote:
> POSIX allows for <math.h> functions to also be defined as macros.
> Currently, only log2 and log2f are so defined.
> 
> These macros pose problems with a few projects which define their
> own static/inline/template log2() (off the top of my head, I can
> think of 2: the CRAN rgl module, and OpenCV; both are C++).  Of
> course, those can be fixed with an #undef log2 after the #include's.
> 
> However, I just encountered tonight a much larger conflict:
> OpenMP/C++ and <math.h> are incompatible.  STC attached:
> 
> $ g++ -D_GLIBCXX_PARALLEL -fopenmp openmp.cxx -lgomp
> In file included from
> /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/parallel/algobase.h:46,
>                  from /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/stl_algobase.h:1137,
>                  from
> /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/char_traits.h:46,
>                  from /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/ios:46,
>                  from
> /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/ostream:45,
>                  from
> /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/iostream:45,
>                  from openmp.cxx:7:
> /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/parallel/base.h:112:
> error: expected `)' before ?/? token
> 
> It gets even worse if you #include <algorithm> as well, and no, it
> doesn't help to #include <cmath>, although moving the math include
> after all other includes does work.
> 
> I see two possible solutions:
> 
> 1) Make the log2 macros dependent on #ifndef __cplusplus;
> 2) Make the parallel/* headers #undef log2 and log2f.
> 
> Thoughts?

Sounds good to me, but that's really one for the newlib list since that
affects all platforms.  Would you mind to repost it there?


Thanks,
Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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