Re: [configure.ac/uClinux] Adding code for fork/vfork?

[Bob Friesenhahn]

On Thu, 14 Apr 2011, Gilles wrote:
> However, some applications use if/else blocks just as this one instead
> of eg. "#ifdef HAVE_FOR" conditional compiling:
> ============
> if (uClinux) {
>         *pid = vfork();
> } else {
>         *pid = fork();
> }
> ============
>
> Is it possible to modify configure.ac so that it goes ahead and
> compiles applications that handle fork/vfork without preprocessor
> commands?

The proper solution for this is to have configure test for both fork() 
and vfork() (and maybe posix_spawn()).  Then you have to decide which 
one you prefer:

In configure.ac:

AC_CHECK_FUNCS([fork posix_spawnp spawnvp vfork])

In the program:

#if HAVE_VFORK
  use vfork
#if HAVE_POSIX_SPAWNP
  use posix_spawn
#if HAVE_SPAWNVP
  use spawnvp
#elif HAVE_FORK
  use fork
#else
#error Need a way to fork a program!
#else

Vfork was supposed to be antique and going away but has been making a 
resurgence in heavily-threaded programs, however, posix_spawnp() is 
still preferred in that case (when available).

Bob
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/