Professional Multicore Programming: Design and Implementation for C++ Developers

Name

NAME

pthread_once — dynamic package initialization

SYNOPSIS

THR #include <pthread.h>

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

DESCRIPTION

The first call to pthread_once() by any thread in a process, with a given once_control, shall call the init_routine with no arguments. Subsequent calls of pthread_once() with the same once_control shall not call the init_routine. On return from pthread_once(), init_routine shall have completed. The once_control parameter shall determine whether the associated initialization routine has been called.

The pthread_once() function is not a cancelation point. However, if init_routine is a cancelation point and is canceled, the effect on once_control shall be as if pthread_once() was never called.

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

The behavior of pthread_once() is undefined if once_control has automatic storage duration or is not initialized by PTHREAD_ONCE_INIT.

RETURN VALUE

Upon successful completion, pthread_once() shall return zero; otherwise, an error number shall be returned to indicate the error.

ERRORS

The pthread_once() function may fail if:

[EINVAL]

If either once_control or init_routine is invalid.

The pthread_once() function shall not return an error code of [EINTR].

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

Some C libraries are designed for dynamic initialization. That is, the global initialization for the library is performed ...