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When a thread is created with a user-supplied stack, the user must reserve enough space to run this thread. In a dynamically linked execution environment, it is very hard to know what the minimum
stack requirments are for a thread. The function thr_min_stack() returns the amount of space needed to execute a null thread. This is a thread that was created to execute a null procedure.
A thread that does something useful should have a stack size that is thr_min_stack() + <some increment>.
Most users should not be creating threads with user-supplied stacks. This functionality was provided to support applications that wanted complete control over their execution environment.
Typically, users should let the threads library manage stack allocation. The threads library provides default stacks which should meet the requirements of any created thread.
thr_min_stack() will return the unsigned int THR_MIN_STACK, which is the minimum-allowable size for a thread's stack.
In this implementation the default size for a user-thread's stack is one mega-byte. If the second argument to thr_create(3THR) is NULL, then the default stack size for the newly-created thread will be used. Otherwise, you may specify a stack-size that
is at least THR_MIN_STACK, yet less than the size of your machine's virtual memory.
It is recommended that the default stack size be used.
To determine the smallest-allowable size for a thread's stack, execute the following:
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/* cc thisfile.c -lthread */
#define _REENTRANT
#include <thread.h>
#include <stdio.h>
main() {
printf("thr_min_stack() returns %u\n",thr_min_stack());
}
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