What is pthread key?

Description: The pthread_key_create() function creates a thread-specific data key that’s available to all threads in the process and binds an optional destructor function destructor to the key. If the function completes successfully the new key is returned in key.

What is pthread_ key_ t?

General description. Creates a key identifier, associated with key, and returns the key identifier into the storage area of type pthread_key_t. At this point, each of the threads in the application has the use of that key, and can set its own unique value by use of pthread_setspecific().

What is pthread_ key_ create used for?

The pthread_key_create() function creates a thread local storage key for the process and associates the destructor function with that key. After a key is created, that key can be used to set and get per-thread data pointer. When pthread_key_create() completes, the value associated with the newly created key is NULL.

What is pthread_key_create () in C++?

int pthread_key_create (pthread_key_t * key, void (*destructor) (void*)); The pthread_key_create () function shall create a thread-specific data key visible to all threads in the process. Key values provided by pthread_key_create () are opaque objects used to locate thread-specific data.

Is it safe to call pthread_key_create () from a destructor?

If an application does not call pthread_exit () from a signal handler, or if it blocks any signal whose handler may call pthread_exit () while calling async-unsafe functions, all functions may be safely called from destructors. There were requests to make pthread_key_create () idempotent with respect to a given key address parameter.

Why can’t I create another thread-specific data key?

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. Insufficient memory exists to create the key.

How are keys and threads associated with each key value?

Upon key creation, the value NULL shall be associated with the new key in all active threads. Upon thread creation, the value NULL shall be associated with all defined keys in the new thread. An optional destructor function may be associated with each key value.