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Name

pthread_once - dynamic package initialization

Synopsis

#include <pthread.h>

pthread_once_t once_control = PTHREAD_ONCE_INIT;

int pthread_once(pthread_once_t *once_control, void (*init_routine)(void));

MT-Level

MT-Safe

Description

If any thread in a process with a once_control parameter makes a call to pthread_once(), the first call will summon the init_routine(), but subsequent calls will not. The once_control parameter determines whether the associated initialization routine has been called. The init_routine() is complete upon return of pthread_once().

pthread_once() is not a cancellation point; however, if the function init_routine() is a cancellation point and is canceled, the effect on once_control is the same as if pthread_once() had never been called.

The constant PTHREAD_ONCE_INIT is defined in the <pthread.h> header.

If once_control has automatic storage duration or is not initialized by PTHREAD_ONCE_INIT , the behavior of pthread_once() is undefined.

Return Values

pthread_once() returns 0 upon successful completion; otherwise, an error number is returned.

Errors

EINVAL
once_control or init_routine is NULL .

Notes

Solaris threads do not offer this functionality.

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