pthread_once - dynamic package initialisation
#include <pthread.h> int pthread_once(pthread_once_t *once_control, void (*init_routine)(void)); pthread_once_t once_control = PTHREAD_ONCE_INIT;
The first call to pthread_once() by any thread in a process, with a given once_control, will call the init_routine() with no arguments. Subsequent calls of pthread_once() with the same once_control will not call the init_routine(). On return from pthread_once(), it is guaranteed that init_routine() has completed. The once_control parameter is used to determine whether the associated initialisation routine has been called.
The function pthread_once() is not a cancellation point. However, if init_routine() is a cancellation point and is canceled, the effect on once_control is as if pthread_once() was never called.
The constant PTHREAD_ONCE_INIT is defined by the header <pthread.h>.
The behaviour of pthread_once() is undefined if once_control has automatic storage duration or is not initialised by PTHREAD_ONCE_INIT.
Upon successful completion, pthread_once() returns zero. Otherwise, an error number is returned to indicate the error.
No errors are defined.
The pthread_once() function will not return an error code of [EINTR].
Derived from the POSIX Threads Extension (1003.1c-1995)