Will the memory in the heap be released when I do pthread_cancel on iOS?

Lets say I have allocated some memory in my background thread, that is, a thread stack is holding a pointer to that memory. Now I want do terminate background thread execution by calling pthread_cancel on it. Will that memory be released or not? (My platform 开发者_StackOverflow社区is iOS, compiler is gcc 4.2)

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Each thread by necessity requires its own stack; however there is typically only one heap per process. When a thread is destroyed, there is no automatic mechanism to free the memory allocated on the heap. All you end up with is a memory leak.

As a general rule, avoid using pthread_cancel since it is hard to ensure that pthread_cancel will run safely. Rather build in some mechanism where you can pass a message to the thread to destroy itself (after freeing any resources that it owns).

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The thread stack will be removed once the thread exits. But there will be no process or code that will look into your thread stack and release any references for the objects that you've allocated on the heap. Also, typically, thread stacks don't hold any references to the memory, the thread stack is an independent space that is given to the thread to use for generic program stack, any reference will only be on the stack for as long as you are inside the function that pushed such a reference onto the stack, typically because you are referencing it with a local variable.

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by default, no -- see other answers, which are more specific to the answer you seek. there is however, such a thing as a thread-specific allocator; if you were using one, you'd know.

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No, it won't be deleted or freed automatically. If you're very lucky, it might be garbage collected sometime if you're running a collector. File handles, shared memory ids, mutexes etc. won't be released/deallocated either. Async cancellation is safe for e.g. pure maths calculations on data still owned by another thread, but very risky in general - that's why some threading APIs have experimented with and removed the function completely.