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

Name

NAME

pthread_getspecific, pthread_setspecific — thread-specific data management

SYNOPSIS

THR #include <pthread.h>

    void *pthread_getspecific(pthread_key_t key);
    int pthread_setspecific(pthread_key_t key, const void *value)

DESCRIPTION

The pthread_getspecific() function shall return the value currently bound to the specified key on behalf of the calling thread.

The pthread_setspecific() function shall associate a thread-specific value with a key obtained via a previous call to pthread_key_create(). Different threads may bind different values to the same key. These values are typically pointers to blocks of dynamically allocated memory that have been reserved for use by the calling thread.

The effect of calling pthread_getspecific() or pthread_setspecific() with a key value not obtained from pthread_key_create() or after key has been deleted with pthread_key_delete() is undefined.

Both pthread_getspecific() and pthread_setspecific() may be called from a thread-specific data destructor function. A call to pthread_getspecific() for the thread-specific data key being destroyed shall return the value NULL, unless the value is changed (after the destructor starts) by a call to pthread_setspecific(). Calling pthread_setspecific() from a thread-specific data destructor routine may result either in lost storage (after at least PTHREAD_DESTRUCTOR_ITERATIONS attempts at destruction) or in an infinite loop.

Both functions may be implemented as macros.

RETURN VALUE

The pthread_getspecific() function ...