cosmopolitan/libc/thread/pthread_key_delete.c

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/errno.h"
#include "libc/intrin/atomic.h"
#include "libc/thread/posixthread.internal.h"
#include "libc/thread/thread.h"

/**
 * Deletes TLS slot.
 *
 * This function should only be called if all threads have finished
 * using the key registration. If a key is used after being deleted
 * then the behavior is undefined. If `k` was not registered by the
 * pthread_key_create() function then the behavior is undefined.
 *
 * @param key was created by pthread_key_create()
 * @return 0 on success, or errno on error
 */
int pthread_key_delete(pthread_key_t k) {
  unassert(0 <= k && k < PTHREAD_KEYS_MAX);
  unassert(atomic_load_explicit(_pthread_key_dtor + k, memory_order_acquire));
  atomic_store_explicit(_pthread_key_dtor + k, 0, memory_order_release);
  return 0;
}