POSIX in g++

[Peng Yu]

On Tue, Jul 15, 2008 at 5:57 PM, Ian Lance Taylor <iant@google.com> wrote:
> "Peng Yu" <pengyu.ut@gmail.com> writes:
>
>> There is an options -ansi to make g++ ANSI compatible. I'm wondering
>> if there is an option to make g++ POSIX compatible. Or g++ is already
>> POSIX compatible without an option?
>
> POSIX itself specifies features macros which you may define to compile
> your source code in a strict POSIX environment.  These are
> _POSIX_SOURCE and _POSIX_C_SOURCE.  These affect the header files
> rather than the libraries.  To get a strict POSIX compiler, use those
> in conjunction with -ansi or -std.

Hi Ian,

Isn't ANSI C++ a subset of POSIX C++. Why do I need to specify
_POSIX_SOURCE,  _POSIX_C_SOURCE and -ansi?

Would you please let me know what is the difference between the option
-ansi and -std?

Thanks,
Peng