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Overview
Comment:Specifying an invalid mutex implementation (via SQLITE_CONFIG_MUTEX) should cause the default one to be used instead.
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SHA1: 1a97bc81ccfc88f2dd527dff16e9e395718675bc
User & Date: mistachkin 2015-09-12 04:19:51.382
Context
2015-09-12
04:22
Fix comments. (check-in: de3fa51e93 user: mistachkin tags: mutexInitCmpSwap)
04:19
Specifying an invalid mutex implementation (via SQLITE_CONFIG_MUTEX) should cause the default one to be used instead. (check-in: 1a97bc81cc user: mistachkin tags: mutexInitCmpSwap)
03:40
Clarify the new mutex implementation reset logic in sqlite3_shutdown(). (check-in: f9a034834e user: mistachkin tags: mutexInitCmpSwap)
Changes
Side-by-Side Diff Ignore Whitespace Patch
Changes to src/mutex.c.
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** allocate a mutex while the system is uninitialized.
*/
static SQLITE_WSD int mutexIsInit = 0;
#endif /* SQLITE_DEBUG && !defined(SQLITE_MUTEX_OMIT) */


#ifndef SQLITE_MUTEX_OMIT
/*
** This structure is for use by sqlite3MutexInit() only.  It represents an
** invalid mutex implementation (i.e. one where all the function pointers
** are null).
*/
static const sqlite3_mutex_methods mutexNullMethods = {
  0, /* xMutexInit */
  0, /* xMutexEnd */
  0, /* xMutexAlloc */
  0, /* xMutexFree */
  0, /* xMutexEnter */
  0, /* xMutexTry */
  0, /* xMutexLeave */
  0, /* xMutexHeld */
  0  /* xMutexNotheld */
};

/*
** Returns non-zero if the currently configured mutex implemention is
** invalid (i.e. all of its function pointers are null).
*/
static int mutexIsInvalid(void){
  return memcmp(&sqlite3GlobalConfig.mutex, &mutexNullMethods,
                sizeof(sqlite3_mutex_methods))==0;
}

/*
** Copies a mutex implementation.  Both arguments must point to valid
** memory.
*/
static void mutexCopy(
  sqlite3_mutex_methods *pTo,
  sqlite3_mutex_methods const *pFrom
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/*
** Initialize the mutex system.
*/
int sqlite3MutexInit(void){ 
  int rc;
  if( sqlite3CompareAndSwap((void * volatile *)&sqlite3GlobalConfig.pMutex,
                            0, &sqlite3GlobalConfig.mutex)==0 ){
                   0, &sqlite3GlobalConfig.mutex)==0 || mutexIsInvalid() ){
    /* If the xMutexAlloc method has not been set, then the user did not
    ** install a mutex implementation via sqlite3_config() prior to 
    ** sqlite3_initialize() being called. This block copies pointers to
    ** the default implementation into the sqlite3GlobalConfig structure.
    */
    sqlite3_mutex_methods const *pFrom;
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