Defined in header <threads.h>
void tss_delete( tss_t tss_id );
(since C11)

Destroys the thread-specific storage identified by tss_id.

The destructor, if one was registered by tss_create, is not called (they are only called at thread exit, either by thrd_exit or by returning from the thread function), it is the responsibility of the programmer to ensure that every thread that is aware of tss_id performed all necessary cleanup, before the call to tss_delete is made.

If tss_delete is called while another thread is executing destructors for tss_id, it's unspecified whether this changes the number of invocations to the associated destructor.

If tss_delete is called while the calling thread is executing destructors, then the destructor associated with tss_id will not be executed again on this thread.


tss_id - thread-specific storage key previously returned by tss_create and not yet deleted by tss_delete

Return value



The POSIX equivalent of this function is pthread_key_delete.

The reason tss_delete never calls destructors is that the destructors (called at thread exit) are normally intended to be executed by the same thread that originally set the value (via tss_set) that the destructor will be dealing with, and may even rely on the values of that or other thread-specific data as seen by that thread. The thread executing tss_delete has no access to other threads' TSS. Even if it were possible to call the destructor for each thread's own value associated with tss_id, tss_delete would have to synchronize with every thread if only to examine whether the value of this TSS in that thread is null (destructors are only called against non-null values).



  • C17 standard (ISO/IEC 9899:2018):
    • The tss_delete function (p: 282)
  • C11 standard (ISO/IEC 9899:2011):
    • The tss_delete function (p: 386)

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