tss_create

 

C

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Concurrency support (C11)

Technical Specifications

Symbol index

 

Concurrency support library

Threads thrd_create thrd_equal thrd_current    thrd_sleep thrd_yield thrd_exit thrd_detach thrd_join thrd_successthrd_timedoutthrd_busythrd_nomemthrd_error    Atomic operations atomic_init ATOMIC_VAR_INIT (until C23) ATOMIC_***_LOCK_FREE atomic_is_lock_free atomic_store atomic_load atomic_exchange atomic_compare_exchange atomic_fetch_add atomic_fetch_sub atomic_fetch_or atomic_fetch_xor atomic_fetch_and

Atomic flags atomic_flag ATOMIC_FLAG_INIT atomic_flag_test_and_set atomic_flag_clear Memory ordering memory_order kill_dependency atomic_thread_fence atomic_signal_fence Mutual exclusion mtx_init mtx_lock mtx_timedlock mtx_trylock call_once mtx_unlock mtx_destroy mtx_plainmtx_recursivemtx_timed Condition variables cnd_init cnd_signal cnd_broadcast cnd_wait cnd_timedwait cnd_destroy Thread-local storage thread_local TSS_DTOR_ITERATIONS    tss_create tss_get tss_set tss_delete

 

Defined in header <threads.h>
int tss_create( tss_t* tss_key, tss_dtor_t destructor );		(since C11)

Creates new thread-specific storage key and stores it in the object pointed to by tss_key. Although the same key value may be used by different threads, the values bound to the key by tss_set are maintained on a per-thread basis and persist for the life of the calling thread.

The value NULL is associated with the newly created key in all existing threads, and upon thread creation, the values associated with all TSS keys is initialized to NULL.

If destructor is not a null pointer, then also associates the destructor which is called when the storage is released by thrd_exit (but not by tss_delete and not at program termination by exit).

A call to tss_create from within a thread-specific storage destructor results in undefined behavior.

Parameters

tss_key	-	pointer to memory location to store the new thread-specific storage key
destructor	-	pointer to a function to call at thread exit

Notes

The POSIX equivalent of this function is pthread_key_create.

Return value

thrd_success if successful, thrd_error otherwise.

Example

int thread_func(void *arg) {
    tss_t key;
    if (thrd_success == tss_create(&key, free)) {
        tss_set(key, malloc(4)); // stores a pointer on TSS
        // ...
    }
} // calls free() for the pointer stored on TSS

References

• C17 standard (ISO/IEC 9899:2018):

• 7.26.6.1 The tss_create function (p: 281-282)

• C11 standard (ISO/IEC 9899:2011):

• 7.26.6.1 The tss_create function (p: 386)