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Date: Wed, 15 Jan 2014 10:08:35 +0100
Message-ID: <CAGAuH46E+FWFt_vMDOyQiEKLANRmJ8KydX-YcKfrFm=UeHy3uw@mail.gmail.com>
Subject: g++: <cmath> is missing C++11 functions
From: Achille Fouilleul <achille DOT fouilleul AT gadz DOT org>
To: cygwin AT cygwin DOT com
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Hi,

On cygwin64, g++ -std=c++11 fails to compile simple programs like this one:

#include <cstdio>
#include <cmath>

int main()
{
  std::printf("%d\n", (int)std::lround(1.23));
  return 0;
}

rr.cpp: In function ‘int main()’:
rr.cpp:6:28: error: ‘lround’ is not a member of ‘std’
   std::printf("%d\n", (int)std::lround(1.23));
                            ^
rr.cpp:6:28: note: suggested alternative:
In file included from
/usr/lib/gcc/x86_64-pc-cygwin/4.8.2/include/c++/cmath:44:0,
                 from rr.cpp:2:
/usr/include/math.h:278:17: note:   ‘lround’
 extern long int lround _PARAMS((double));

I have noticed that C++11 cmath functions are declared in the std
namespace only if _GLIBCXX_USE_C99_MATH_TR1 is defined.
It's not:
/usr/lib/gcc/x86_64-pc-cygwin/4.8.2/include/c++/x86_64-pc-cygwin/bits/c++config.h:1272:/*
#undef _GLIBCXX_USE_C99_MATH_TR1 */

Regards,
Achille

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