thread stack size on Windows (Visual C++)

Question

Is there a call to determine the stack size of a running thread? I've been looking in MSDN thread functions documentation, and can't seem to find one.

Answer 1

Whilst there isn't an API to find out stack size directly, contiguous virtual address space must be reserved up to the maximum stack size - it's just that a lot of that space isn't committed yet. You can take advantage of this and make two calls to VirtualQuery.

For the first call, pass it the address of any value on the stack to get the base address and size, in bytes, of the committed stack space. On an x86 machine where the stack grows downwards, subtract the size from the base address and VirtualQuery again: this will give you the size of the space reserved for the stack (assuming you're not precisely on the limit of stack size at the time). Summing the two naturally gives you the total stack size.

Answer 2

You can get the current committed size from the Top and Bottom in the TEB. You can get the process initial reserve and commit sizes from the PE header. But you cannot retrieve the actual sizes passed to CreateThread, nor is there any API to get the remaining size of reserved nor committed from current stack, see Thread Stack Size.