Specifying thread stack size in pthreads

Question

I want to increase the stack size of a thread created through pthread_create(). The way to go seems to be

int pthread_attr_setstack( pthread_attr_t *attr,
                           void *stackaddr,
                           size_t stacksize );

from pthread.h.

However, according to multiple online references,

The stackaddr shall be aligned appropriately to be used as a stack; for example, pthread_attr_setstack() may fail with [EINVAL] if ( stackaddr & 0x7) is not 0.

My question: could someone provide an example of how to perform the alignment? Is it (the alignment) platform or implementation dependent?

Thanks in advance

score 13 · Accepted Answer · answered Mar 24 '11 at 16:11

13

Never use pthread_attr_setstack. It has a lot of fatal flaws, the worst of which is that it is impossible to ever free or reuse the stack after a thread has been created using it. (POSIX explicitly states that any attempt to do so results in undefined behavior.)

POSIX provides a much better function, pthread_attr_setstacksize which allows you to request the stack size you need, but leaves the implementation with the responsibility for allocating and deallocating the stack.

answered Mar 24 '11 at 16:11

R.. GitHub STOP HELPING ICE

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Thanks for the categorical answer :) – abeln Mar 24 '11 at 16:37
No problem. :-) Another flaw I failed to mention is that there's no portable way of setting up guard pages with `pthread_attr_setstack`, so stack overflows will lead to memory corruption with likely-dangerous consequences rather than just `SIGSEGV`. – R.. GitHub STOP HELPING ICE Mar 24 '11 at 16:50

score 1 · Answer 2 · answered Mar 24 '11 at 16:04

1

Look into posix_memalign().

It will allocate a memory block of the requested alignment and size.

answered Mar 24 '11 at 16:04

Zan Lynx

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Specifying thread stack size in pthreads

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