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Date: Mon, 21 Jun 2010 14:26:00 -0000
Subject: [Bug c++/44611]  New: Including <math,h> and <cmath> hides ::signbit function
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When both of these files are included - compiler cannot locate c global signbit
function.

adrianc@dluadrianc:~/gcc_bug> g++ signbit.cc
signbit.cc: In function 'int main(int, char**)':
signbit.cc:18:42: error: 'signbit' was not declared in this scope

#include <iostream>
#include <math.h>
#include <cmath>

int main(int argc, char *argv[])
{
   float a=12.4234;
   float b=-123.4333;

#ifdef _XOPEN_SOURCE
   std::cout << "_XOPEN_SOURCE=" << _XOPEN_SOURCE << std::endl;
#endif

#ifdef _ISOC99_SOURCE
   std::cout << "_ISOC99_SOURCE is here\n";
#endif

   std::cout << "signbit a=" << signbit(a) << std::endl;
   std::cout << "signbit b=" << signbit(b) << std::endl;

   return 0;
}


adrianc@dluadrianc:~/gcc_bug> gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/i686-pc-linux-gnu/4.5.0/lto-wrapper
Target: i686-pc-linux-gnu
Configured with: ../gcc-4.5.0/configure --enable-__cxa_atexit
--enable-languages=c,c++ --enable-threads --with-cpu=core2 --disable-nls
--with-arch=i686 --with-mpfr=/usr/local --with-gmp=/usr/local
--with-mpc=/usr/local --with-build-time-tools=/usr/local --enable-lto
Thread model: posix
gcc version 4.5.0 (GCC)


-- 
           Summary: Including <math,h> and <cmath> hides ::signbit function
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: gnu at bluedreamer dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44611