libpthread: Remove unneeded NULL checks from semaphore functions

src/untrusted/pthread/nc_semaphore.c

 /*
  * Copyright (c) 2011 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 /*
 * Native Client semaphore API
 */
 
@@ skipping 28 matching lines @@
  * creates a thundering herd problem.  If the woken threads wake
  * quickly enough, all but one of them will fail to decrement the
  * semaphore count and will wait again.  Because of this problem, I've
  * chosen not to use this algorithm.  sem_post() below wakes only a
  * single thread.
  */
 
 
 /* Initialize semaphore  */
 int sem_init(sem_t *sem, int pshared, unsigned int value) {
-  if (NULL == sem) {
-    errno = EINVAL;
-    return -1;
-  }
   if (pshared) {
     /* We don't support shared semaphores yet. */
     errno = ENOSYS;
     return -1;
   }
   if (value > SEM_VALUE_MAX) {
     errno = EINVAL;
     return -1;
   }
   sem->count = value;
   sem->nwaiters = 0;
   return 0;
 }
 
 int sem_destroy(sem_t *sem) {
-  if (NULL == sem) {
-    errno = EINVAL;
-    return -1;
-  }
   if (sem->nwaiters != 0) {
     errno = EBUSY;
     return -1;
   }
   return 0;
 }
 
 static int decrement_if_positive(volatile int *ptr) {
   int old_value;
   do {
     old_value = *ptr;
     if (old_value == 0)
       return 0;
   } while (!__sync_bool_compare_and_swap(ptr, old_value, old_value - 1));
   return 1;
 }
 
 int sem_wait(sem_t *sem) {
-  if (NULL == sem) {
-    errno = EINVAL;
-    return -1;
-  }
-
   if (decrement_if_positive(&sem->count))
     return 0;
 
   __sync_fetch_and_add(&sem->nwaiters, 1);
   do {
     __nc_irt_futex.futex_wait_abs(&sem->count, 0, NULL);
   } while (!decrement_if_positive(&sem->count));
   __sync_fetch_and_sub(&sem->nwaiters, 1);
   return 0;
 }
 
 int sem_post(sem_t *sem) {
-  if (NULL == sem) {
-    errno = EINVAL;
-    return -1;
-  }
-
   /* Increment sem->count, checking for overflow. */
   int old_value;
   do {
     old_value = sem->count;
     if (old_value == SEM_VALUE_MAX) {
       errno = EOVERFLOW;
       return -1;
     }
   } while (!__sync_bool_compare_and_swap(&sem->count, old_value,
                                          old_value + 1));
 
   /*
    * We only need to call futex_wake() if there are waiters.  Note
    * that this might do an unnecessary call to futex_wake() if the
    * last waiter has already been woken using futex_wake() but has not
    * yet decremented sem->nwaiters.
    */
   if (sem->nwaiters != 0) {
     int woken_count;
     __nc_irt_futex.futex_wake(&sem->count, 1, &woken_count);
   }
   return 0;
 }