pthread_key_create()

thread-specific data key creation 

Function

SYNOPSIS

#include <pthread.h>

int pthread_key_create(pthread_key_t *key, void (*destructor)(void *));

DESCRIPTION

The pthread_key_create() function creates a thread-specific data key visible to all threads in the process. Key values created by pthread_key_create() are opaque objects used to locate thread-specific data. Although the same key value may be used by different threads, the values bound to the key pthread_setspecific() are maintained on a per-thread basis and persist for the life of the calling thread.

Upon key creation, the value NULL is associated with the new key in all active threads. Upon thread creation, the value NULL is associated with all defined keys in the new thread.

An optional destructor function may be associated with each key value. At thread exit, if a key value has a non-NULL destructor pointer, and the thread has a non-NULL value associated with that key, the function pointed to is called with the current associated value as its sole argument. The order of destructor calls is unspecified if more than one destructor exists for a thread when it exits.

If, after all destructors have been called for all non-NULL values with associated destructors, there are still some non-NULL values with associated destructors, then the process is repeated, up to a maximum of PTHREAD_DESTRUCTOR_ITERATIONS iterations.

PARAMETERS

key 

Is the location where the newly allocated key value is stored.

destructor 

Is the destructor function to run on thread exit. This may be set to NULL if no destructor function is required.

RETURN VALUES

On success, pthread_key_create() returns 0. On error, one of the following values is returned:

EAGAIN 

The system lacked the necessary resources to create another thread-specific data key, or the system-imposed limit on the total number of keys per process PTHREAD_KEYS_MAX has been exceeded.

ENOMEM 

Insufficient memory exists to create the key.

EFAULT 

key is an invalid pointer.

CONFORMANCE

POSIX P1003.1 (1996)

MULTITHREAD SAFETY LEVEL

MT-safe.

PORTING ISSUES

None.

AVAILABILITY

MKS Toolkit for Professional Developers
MKS Toolkit for Enterprise Developers
MKS Toolkit for Enterprise Developers 64-Bit Edition

SEE ALSO

Functions:
pthread_exit(), pthread_getspecific(), pthread_key_delete(), pthread_setspecific()

MKS Toolkit 9.2 Documentation Build 16.