Subj : Re: How to deal with errno in a multipthread program
To   : comp.programming.threads
From : Sean Burke
Date : Mon Apr 18 2005 09:38 pm



Paul Pluzhnikov <ppluzhnikov-nsp@charter.net> writes:

> Eric Sosman <eric.sosman@sun.com> writes:
> 
> >     However, you do not need to worry.  The thread
> > implementation itself arranges to have a unique `errno'
> > for each thread:
> 
> Minor correction: the thread implementation will do so *provided*
> you compile your program correctly for MT execution.
> 
> On Solaris, that means adding '-mt' flag if using WorkShop compilers
> or '-pthreads' if using gcc.
> 
> On Linux, errno is thread-safe without any flags at all, but
> '-pthread' ([1]) is recommended anyway.
> 
> On AIX, -D_THREADS is required (IIRC).
> 
> The OP should read his compiler documentation and/or system headers
> to figure out what (if anything) is needed on his platform.
> 
> Cheers,
> 
> [1] Yes, this is not a typo: the Solaris and Linux gcc options
> differ: '-pthreads' vs. '-pthread'. There might be a good reason
> for this, but I do not know it. If you do, please let me know.


It doesn't appear that anyone else mentioned this, 
so let me add that it is important to #include <errno.h>.
Simply doing

	extern int errno;

does not suffice.

-SEan

.