Re: Bug#126703: g++-3.0: <stdio.h> defines _GNU_SOURCE with g++-3.0

["Martin v. Loewis" <martin@v.loewis.de>]

> > > possibly include a glibc header, otherwise certain C++ programs will
> > > simply fail out of the box.
> > 
> > I don't believe that this is true.
> [...]
> > >     http://gcc.gnu.org/ml/libstdc++/2000-12/msg00215.html
> 
> Well, there's my example.  :-)

Just to make sure we are talking about the same example: You are
trying to compile

#include <stdlib.h>
#include <cstdlib>

with g++. Currently, this fails because the header files cannot
re-export symbols (starting with a failure to re-export lldiv_t).

> You are aware that this code is currently unused by default, and unused
> by Debian, right?  Only one of {c,c_std,c_shadow} is used.

The same strategy applies to any setup. Please modify your installed
c++config.h to read

// Define if C99 features such as lldiv_t, llabs, lldiv should be exposed.
#ifdef __USE_ISOC99
#define _GLIBCPP_USE_C99 1
#endif

then, compile

#undef _GNU_SOURCE
#include <stdlib.h>
#include <cstdlib>

int main(){}

with the installed g++ 3. It compiles fine for me.

Now you may argue that

#undef _GNU_SOURCE
#include <stdlib.h>
#include <cstdlib>

int main(){
    std::lldiv_t x;
}

won't compile anymore, with that change, since lldiv_t is not
available to the application. This is not a problem, since C++98 does
not mandate that cstdlib offers std::lldiv_t. Anybody wanting to
compile a C++ program that uses C99 features should define either
_ISOC99_SOURCE or _GNU_SOURCE.

Regards,
Martin