tss_set

 

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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_set( tss_t tss_id, void *val );		(since C11)

Sets the value of the thread-specific storage identified by tss_id for the current thread to val. Different threads may set different values to the same key.

The destructor, if available, is not invoked.

Parameters

tss_id	-	thread-specific storage key, obtained from tss_create and not deleted by tss_delete
val	-	value to set thread-specific storage to

Return value

thrd_success if successful, thrd_error otherwise.

Notes

The POSIX equivalent of this function is pthread_setspecific.

Typically TSS is used to store pointers to blocks of dynamically allocated memory that have been reserved for use by the calling thread.

tss_set may be called in the TSS destructor. If the destructor exits with non-NULL value in the TSS storage, it will be retried by thrd_exit up to TSS_DTOR_ITERATIONS times, after which the storage will be lost.

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):

• 7.26.6.4 The tss_set function (p: 282-283)

• C11 standard (ISO/IEC 9899:2011):

• 7.26.6.4 The tss_set function (p: 387)

See also

tss_get (C11)

reads from thread-specific storage (function)