Re: g++4.9.2 fails to compile standard C++11 code

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Mar 13 09:13, Csaba Raduly wrote:
> Hi
> 
> On Thu, Mar 12, 2015 at 10:55 AM, Duncan Roe  wrote:
> > On Wed, Mar 11, 2015 at 06:55:16PM -0400, Vlad Gheorghiu wrote:
> >> The following code fails to compile under latest cygwin, Windows 7,
> >> g++4.9.2. Compiled with g++ -std=c++11 test.cpp. The compiler
> >> complains that std::log2 is not a member of std.
> >>
> >>     #include <cmath>
> >>     #include <iostream>
> >>
> >>     int main()
> >>     {
> >>             auto x = std::log2(10);
> >>             std::cout << x << std::endl;
> >>     }
> >>
> >>
> >> Verbatim error:
> >>
> >>     g++ -std=c++11 test.cpp
> >>     test.cpp: In function 'int main()':
> >>     test.cpp:5:11: error: 'log2' is not a member of 'std'
> >>       auto x = std::log2(10);
> >>                ^
> >>     test.cpp:5:11: note: suggested alternative:
> >>     In file included from
> >> /usr/lib/gcc/i686-pc-cygwin/4.9.2/include/c++/cmath:44:0,
> >>                      from test.cpp:1:
> >>     /usr/include/math.h:305:15: note:   ???log2???
> >>      extern double log2 _PARAMS((double));
> >>
> > FWIW, this program works fine under Linux / gcc4.8.2:
> 
> ISTR a discussion about some C++11 features being configured away due
> to Cygwin's lack of some C library functions ("to_string not a member
> of std"): https://sourceware.org/ml/cygwin/2015-01/msg00245.html
> 
> Your issue may be related (I'm guessing here because I don't have
> Cygwin at hand right now).

I guess the same.  The problem is probably related to the fact that
newlib is still missing most of the long double functions (cosl, sinl,
etc).  The libstdc++ configury seems to activate the related std methods
only if *all* related C library functions for double, float and long
double (e.g. cos, cosf, cosl) are implemented by the platform.


Corinna

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

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