Re: ANSI and GNU regarding compatibility

From:

=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?= <Erik-wikstrom@telia.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 16 Jul 2008 09:15:53 GMT

Message-ID:

<d%ifk.1016$U5.488@newsb.telia.net>

On 2008-07-15 19:05, Peng Yu wrote:

On Jul 15, 5:03 am, Erik Wikstr??m <Erik-wikst...@telia.com> wrote:

On 2008-07-15 05:47, Peng Yu wrote:

Hi,

ANSI and GNU C are different in some delicate aspects (I'm not sure
about C++). For example, M_PI is not in ANSI C but in GNU C.

Of course, to make my program most portable, I should go for ANSI. But
since ANSI lacks some convenient facilities, such as M_PI just
mentioned, I would like to use GNU C.

Now, the question is if a platform has ANSI C, what is the chance it
does not have GNU C? What is the chance that a GNU C can not be
installed at all? If in most platforms that have both ANSI C and GNU
C. Then I should just use GNU C.

If ANSI C is not enough go to the next best thing: POSIX (which, among
other things is where M_PI comes from). All UNIX/Linux systems that I
know of are more or less POSIX compatible and many C and C++ compilers
includes support for POSIX features as well. Building in compiler
dependencies in your code is a bad idea unless you really have to.

I would like my g++ compiler following POSIX. There is an options -
ansi to make it ANSI compatible. Is there an options to make g++ POSIX
compatible? Or g++ is already POSIX compatible without an option?

To my knowledge POSIX does not make any changes or additions to the C
language it only adds a number of library functions, so the compiler
have nothing to do with it.

--
Erik Wikstr??m