You can simply use id_ptr as follows:
void *PrintHello(void *threadid)
{
int *id_ptr, taskid;
id_ptr = (int *) threadid;
taskid = *id_ptr;
printf("Thread %d says hello\n", taskid);
pthread_exit(id_ptr);
}
David Harel wrote:
Thanks for the info, It is very helpful.
The man pages of pthread_exit() says prototype is:
void pthread_exit(void *retval);
In my stupidity I assumed I must return an address of...
Sending the actual value casted to (void *) works well.
Pablo 'merKur' Kohan wrote:
On Thu, 2005-01-06 at 18:17 +0200, David Harel wrote:
Hi,
I hope you can help me. I was looking for the right answer
everywhere on the net.
When I do pthread_exit(retval); and I do pthread_join(&retval); at
the "calling" thread...
[snip]
Still, retval is a pointer, i guess to somewhere in the terminated
thread space (stack frame) but after pthread_join() the terminated
thread space can be reclaimed. What if another thread reclaims that
space and reuse it. Does that mean that retval will be invalid? and
if so.
That's exactly your problem.
You return a pointer (&taskid) to an area you don't own anymore...
So in the best case, you'll get garbage, and when not assigned to one of
your threads, it will SEGV.
How can I save retval safely?
To solve this you can (based on your example):
1) return taskid instead of it's pointer (&taskid), or
2) if you have to return a significant amount of memory, then have it
alloc'ed.
Hope this helps,
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