Re: problem with fprintf and OpenMP

[Jakub Jelinek <jakub at redhat dot com>]

On Thu, May 15, 2014 at 08:01:13AM +0200, Siegmar Gross wrote:
> I'm using gcc-4.9.0 and have a problem with the following program.
> I have reported the problem allready on gcc-help some days ago,
> but didn't get any replies. Perhaps somebody in this list knows,
> if the behaviour is intended.

Yes, this is what OpenMP standard requires.

> #include <stdio.h>
> #include <stdlib.h>
> #include <omp.h>
> 
> int main (void)
> {
>   #pragma omp parallel default (none)
>   fprintf (stderr, "Hello!\n");
>   return EXIT_SUCCESS;
> }
> 
> 
> I can solve the problem if I add "shared(__iob)" to "#pragma",
> but then the program isn't portable any longer.

Or don't use default (none), or don't use stderr directly in the
default(none) parallel region (use a temporary variable, call
a function that implicitly uses stderr, etc.).

> In my opinion the compiler knows that I use OpenMP and that
> I use "default(none)" so that it can automatically add all
> necessary internal variables to the "shared clause" or that

Please define what is internal variable.  __iob is for the compiler
not an internal variable of any kind, stderr is a macro like any other.
Note that e.g. on Linux stderr is a macro and a variable
(#define stderr stderr), treating in that case stderr as an internal
variable would be really weird.

	Jakub