#include <thread.h> size_t thr_min_stack(void);
thr_min_stack() returns the amount of space that is needed to execute a null thread. A null thread is a thread that is created to execute a null procedure. Useful threads need more than the absolute minimum stack size, so be very careful when reducing the stack size.
A thread that executes more than a null procedure should allocate a stack size that is larger than the size of thr_min_stack().
When a thread is created with a user-supplied stack, the user must reserve enough space to run the thread. A dynamically linked execution environment increases the difficulty of determining the thread minimal stack requirements.
You can specify a custom stack in two ways. The first is to supply a NULL for the stack location, thereby asking the runtime library to allocate the space for the stack, but to supply the desired size in the stacksize parameter to thr_create() .
The other approach is to take overall aspects of stack management and supply a pointer to the stack to thr_create(). This means that you are responsible not only for stack allocation but also for stack deallocation. When the thread terminates, you must arrange for the disposal of the thread's stack.
Most users should not create threads with user-supplied stacks. User-supplied stacks exist only to support applications that require complete control over their execution environments.
Instead, users should let the system manage stack allocation. The system provides default stacks that should meet the requirements of any created thread.