Re: Using pthreads in VS .NET 2003

Rayne <>
Wed, 3 Mar 2010 18:02:23 -0800 (PST)
On Mar 4, 6:25 am, Tamas Demjen <> wrote:

Rayne wrote:

   rc = pthread_create(&pthread, &attr, function, (void *)tid[i]);

You are passing a pointer to your new thread, but 1 millisecond later
that pointer gets deleted. Chances are by the time the thread is awake
the pointer is already invalid (addressing random garbage). If this
code works at all, it's due to pure luck (and the Sleep function). There
is a high risk of failure there, and sooner or later you are going to
get into random memory corruption errors, which is going to be extremely
difficult to debug.

One solution would be to free the pointer from the thread instead:
void ThreadFunction(void* param)
    int* pid = (int*)param;
    int id = *pid;

Of course the "free(tid[i]);" line must go away when pthread_create

If you feel really lazy, that void* pointer can be used to hold the
integer value directly:

rc = pthread_create(&pthread, &attr, function, (void *)i);

This is not a very elegant solution, though. It is confusing and very
easy to overlook. It's not what a programmer would expect from a
pointer. Of course the thread will have to treat this pointer as an
integer as well:

void ThreadFunction(void* param)
    int id = (int)param; // careful, void* was reinterpreted as int

Such a thing raises an eyebrow. Another disadvantage is that it
won't let you add a second argument if you need one in the future.
I'd use a pointer to a structure instead.


Thank you for your comprehensive explanation! This was the problem and
freeing the tid[i] value from the worker thread solved it.

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