(void *) (void*) (product) what is it?

(void *) (void*) (product) what is it?

It looks like a cast of product to void*, then another unnecessary cast to void* again.

Quote:

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Originally Posted by laserlight

It looks like a cast of product to void*, then another unnecessary cast to void* again.

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will add context

Code:

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pthread_create(&threads[threadNumber], &attr, dotProduct, (void *)(void*) (product));

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Yeah, that's it. Remove one of the two (void*) as it has no net effect.

pthread_create() seems to take a function pointer to a void* func(void*) type of function. I might be wrong though, the function pointer syntax in C is quite confusing.

Then product should have been defined as such a function; no casting needed. If you do want to cast, use a typedef: but then there's the issue of undefined behaviour if you're not careful.

EDIT:
I can't say I have much experience with casting to function pointer types, and in fact I usually typedef when I do have to deal with function pointers at all, but a quick check shows that if indeed the intention was to cast product to such a function pointer type without benefit of a typedef, it should have been: (void*(*)(void*))product

EDIT #2:
Well, another quick check shows that pthread_create looks like this:

Code:

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int pthread_create(pthread_t *thread, const pthread_attr_t *attr, void *(*start_routine) (void *), void *arg);

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So, cronus, while you're right that pthread_create does take such a function pointer, in alex01's post #3 that would be dotProduct, not the expression in question.

Oh right, hadn't noticed that that weird cast was for just the normal void* argument. Indeed in that case, the second (void*) makes no sense.