'log2' is not a member of 'std'

[Jan Stary]

On Jul 03 03:28:30, jmr at macports.org wrote:
> > This is MacOSX 10.6.8 running various compilers provided by MacPorts.
> > Compiling the following C++ source
> > 
> > 	#include <cmath>
> > 
> > 	int main(void)
> > 	{
> > 		double d = std::log2(2.3456789f);
> > 		return 0;
> > 	}
> > 
> > results in
> > 
> > 	'log2' is not a member of 'std'.
> > 
> > This happens with the system g++, which is i686-apple-darwin10-g++-4.2.1,
> > each of g++-4.0 g++-4.2 g++-mp-5 g++-mp-6, and with clang++-mp-3.4;
> > in each case, I am compiling as $CXX -std=c++11 prog.c
> > 
> > Apparently, there is some relatively recent turmoil about the C++ libs;
> > I don't know much c++ but find myself compiling some third party C++ code.
> > Am I missing something obvious?
> 
> Well the Xcode-supplied g++s and clang would be using the system libstdc++,
> which doesn't support C++11, and std::log2 is a C++11 feature.

OK.

> The g++-mp variants should support it, but seemingly don't because of the
> bug that Ken mentioned, which should be fixed in GCC 7.

Yes, it compiles fine with g++-mp-7 as provided by the gcc7 port.
(Has the bug not been fixed in upstream GGC 5 and GCC 6,
or is it just the gcc5 and gcc6 port that is behind?)

> Clang can support C++11 if you use -stdlib=libc++.

Yes it does: clang++-mp-3.4 -stdlib=libc++ prog.cc 

	Thank you

		Jan