Public bug reported:
Consider the following small test application:
#include <iostream>
#include <cmath>
#include <math.h>
int main()
{
double d = NAN;
std::cout << std::isnan(d) << '\n';
std::cout << isnan(d) << '\n';
return 0;
}
Compiling on Ubuntu 16.04 with g++-5.4.0 using C++11 standard fails:
$ g++ -std=c++11 main.cpp
main.cpp: In function ‘int main()’:
main.cpp:10:25: error: ‘isnan’ was not declared in this scope
std::cout << isnan(d) << '\n';
^
main.cpp:10:25: note: suggested alternative:
In file included from main.cpp:3:0:
/usr/include/c++/5/cmath:641:5: note: ‘std::isnan’
isnan(_Tp __x)
^
I've compiled this on Centos gcc-4.9.1 and gcc-5.2.1 and it works on both.
I've compiled this on Ubuntu gcc-4.9.3 and that too works.
However, compiling on Ununtu gcc-5.4.0 doesn't.
I've also tried several online compilers, with mixed results.
Wandbox has gcc-6.3.0, gcc-5.2.0, gcc-5.1.0 and they all compiled fine.
Godbolt broke for gcc-4.9.2 through gcc-5.3, but then works on 6.1.
Given it works for gcc-5.2.0 on Wandbox and breaks for gcc-5-2.0 on
Godbolt makes me thing one must be using a patched standard library.
** Affects: gcc-5 (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1617838
Title:
std::isnan and isnan visibility problems
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