On 7/27/2015 6:40 PM, Jonathan Wakely wrote:
On 27 July 2015 at 21:22, Edward Diener wrote:
On 7/27/2015 10:57 AM, Jonathan Wakely wrote:
On 27 July 2015 at 14:48, Edward Diener wrote:
On 7/27/2015 4:34 AM, Jonathan Wakely wrote:
On 27 July 2015 at 05:17, Edward Diener wrote:
Try
#if defined(__GXX_EXPERIMENTAL_CXX0X__) || (__cplusplus >= 201103L)
// C++11 is in effect
#endif
GCC 4.8 defines __cplusplus to the correct YYYYMMDD value so this is
not necessary.
I meant it as a general solution for any version of gcc. It is what Boost
config uses.
But it doesn't help if you run the preprocessor in C mode not C++,
since neither will be defined :-)
How is it possible to be compiling for C++11 when running in C mode ?
In other words it does work since a C++11 compile will never be defined when
running in C mode, which is certainly what is wanted.
See the first mail in the thread, which attempted to use the
preprocessor to detect whether C++11 is supported like so:
$ g++ -std=c++11 -dM -E - < /dev/null | grep cplusplus
cc1.exe: warning: command line option '-std=c++11' is valid for
C++/ObjC++ but not for C [enabled by default]=
This is running the preprocessor in C mode. Checking for
__GXX_EXPERIMENTAL_CXX0X__ here won't help, because it's still using
the preprocessor in C mode, i.e. this still fails:
$ g++-4.4.7 -std=c++0x -dM -E - < /dev/null | egrep 'cplusplus|EXPERIMENTAL'
cc1: warning: command line option "-std=c++0x" is valid for C++/ObjC++
but not for C
Whereas this works, because it runs the preprocessor in C++ mode:
$ g++-4.4.7 -std=c++0x -dM -E -x c++ - < /dev/null | egrep
'cplusplus|EXPERIMENTAL'
#define __GXX_EXPERIMENTAL_CXX0X__ 1
#define __cplusplus 1
That's what I meant about running the preprocessor in C mode, not C++ mode.
I see your point. The code I mentioned should really be:
#if defined(__GXX_EXPERIMENTAL_CXX0X__) || defined(__cplusplus) &&
__cplusplus >= 201103L
// C++11 is in effect
#endif
