Re: System call v.s. errno

[Jakub Jelinek <jakub@redhat.com>]

On Wed, May 04, 2005 at 09:22:09AM -0400, Richard B. Johnson wrote:
> Does anybody know for sure if global 'errno' is supposed to
> be altered after a successful system call? I'm trying to
> track down a problem where system calls return with EINTR
> even though all signal handlers are set with SA_RESTART in
> the flags. It appears as though there may be a race somewhere
> because if I directly set errno to 0x1234, within a few
> hundred system calls, it gets set to EINTR even though all
> system calls seemed to return 'good'. This makes it
> hard to trace down the real problem.

http://www.opengroup.org/onlinepubs/009695399/functions/errno.html
is very clear on this.  Unless indicated that errno is valid after a call
(for many syscalls it is valid when the syscall returns -1), errno has
unspecified value.

	Jakub