kc3-lang/SDL/src/thread/generic/SDL_sysmutex.c

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• Hash : 17b43b0f
  Author :
  Date : 2022-10-08T09:32:09
  

  Don't try to create a semaphore for the mutex implementation if threads are disabled Fixes https://github.com/libsdl-org/SDL/issues/6344

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• src/thread/generic/SDL_sysmutex.c

• /*
    Simple DirectMedia Layer
    Copyright (C) 1997-2022 Sam Lantinga <slouken@libsdl.org>
  
    This software is provided 'as-is', without any express or implied
    warranty.  In no event will the authors be held liable for any damages
    arising from the use of this software.
  
    Permission is granted to anyone to use this software for any purpose,
    including commercial applications, and to alter it and redistribute it
    freely, subject to the following restrictions:
  
    1. The origin of this software must not be misrepresented; you must not
       claim that you wrote the original software. If you use this software
       in a product, an acknowledgment in the product documentation would be
       appreciated but is not required.
    2. Altered source versions must be plainly marked as such, and must not be
       misrepresented as being the original software.
    3. This notice may not be removed or altered from any source distribution.
  */
  #include "../../SDL_internal.h"
  
  /* An implementation of mutexes using semaphores */
  
  #include "SDL_thread.h"
  #include "SDL_systhread_c.h"
  
  
  struct SDL_mutex
  {
      int recursive;
      SDL_threadID owner;
      SDL_sem *sem;
  };
  
  /* Create a mutex */
  SDL_mutex *
  SDL_CreateMutex(void)
  {
      SDL_mutex *mutex;
  
      /* Allocate mutex memory */
      mutex = (SDL_mutex *) SDL_calloc(1, sizeof(*mutex));
  
  #if !SDL_THREADS_DISABLED
      if (mutex) {
          /* Create the mutex semaphore, with initial value 1 */
          mutex->sem = SDL_CreateSemaphore(1);
          mutex->recursive = 0;
          mutex->owner = 0;
          if (!mutex->sem) {
              SDL_free(mutex);
              mutex = NULL;
          }
      } else {
          SDL_OutOfMemory();
      }
  #endif /* !SDL_THREADS_DISABLED */
  
      return mutex;
  }
  
  /* Free the mutex */
  void
  SDL_DestroyMutex(SDL_mutex * mutex)
  {
      if (mutex) {
          if (mutex->sem) {
              SDL_DestroySemaphore(mutex->sem);
          }
          SDL_free(mutex);
      }
  }
  
  /* Lock the mutex */
  int
  SDL_LockMutex(SDL_mutex * mutex)
  {
  #if SDL_THREADS_DISABLED
      return 0;
  #else
      SDL_threadID this_thread;
  
      if (mutex == NULL) {
          return SDL_InvalidParamError("mutex");
      }
  
      this_thread = SDL_ThreadID();
      if (mutex->owner == this_thread) {
          ++mutex->recursive;
      } else {
          /* The order of operations is important.
             We set the locking thread id after we obtain the lock
             so unlocks from other threads will fail.
           */
          SDL_SemWait(mutex->sem);
          mutex->owner = this_thread;
          mutex->recursive = 0;
      }
  
      return 0;
  #endif /* SDL_THREADS_DISABLED */
  }
  
  /* try Lock the mutex */
  int
  SDL_TryLockMutex(SDL_mutex * mutex)
  {
  #if SDL_THREADS_DISABLED
      return 0;
  #else
      int retval = 0;
      SDL_threadID this_thread;
  
      if (mutex == NULL) {
          return SDL_InvalidParamError("mutex");
      }
  
      this_thread = SDL_ThreadID();
      if (mutex->owner == this_thread) {
          ++mutex->recursive;
      } else {
          /* The order of operations is important.
           We set the locking thread id after we obtain the lock
           so unlocks from other threads will fail.
           */
          retval = SDL_SemWait(mutex->sem);
          if (retval == 0) {
              mutex->owner = this_thread;
              mutex->recursive = 0;
          }
      }
  
      return retval;
  #endif /* SDL_THREADS_DISABLED */
  }
  
  /* Unlock the mutex */
  int
  SDL_mutexV(SDL_mutex * mutex)
  {
  #if SDL_THREADS_DISABLED
      return 0;
  #else
      if (mutex == NULL) {
          return SDL_InvalidParamError("mutex");
      }
  
      /* If we don't own the mutex, we can't unlock it */
      if (SDL_ThreadID() != mutex->owner) {
          return SDL_SetError("mutex not owned by this thread");
      }
  
      if (mutex->recursive) {
          --mutex->recursive;
      } else {
          /* The order of operations is important.
             First reset the owner so another thread doesn't lock
             the mutex and set the ownership before we reset it,
             then release the lock semaphore.
           */
          mutex->owner = 0;
          SDL_SemPost(mutex->sem);
      }
      return 0;
  #endif /* SDL_THREADS_DISABLED */
  }
  
  /* vi: set ts=4 sw=4 expandtab: */
  

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