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Comment:When the in single-threaded mode, the sqlite3_mutex_alloc() interface still returns a non-NULL value. The mutex doesn't do anything, but it tests non-NULL. This way, extensions (or VFSes) that use sqlite3_mutex_alloc() can tell the difference between an OOM error and mutexes being disabled.
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SHA1: 451fd175758983c335aab449fdc4cb838156c4cb
User & Date: drh 2010-05-05 00:05:24
Context
2010-05-05
00:22
Get the previous mutex fix working with SQLITE_DEBUG and with the amalgamation. check-in: df19928f user: drh tags: trunk
00:05
When the in single-threaded mode, the sqlite3_mutex_alloc() interface still returns a non-NULL value. The mutex doesn't do anything, but it tests non-NULL. This way, extensions (or VFSes) that use sqlite3_mutex_alloc() can tell the difference between an OOM error and mutexes being disabled. check-in: 451fd175 user: drh tags: trunk
2010-05-04
18:50
When sqlite3PagerPagecount() is called without any locks, always return the physical file size, not the logical file size. check-in: 4016b422 user: drh tags: trunk
Changes
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Changes to src/mutex.c. 

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#ifndef SQLITE_MUTEX_OMIT
/*
** Initialize the mutex system.
*/
int sqlite3MutexInit(void){ 
  int rc = SQLITE_OK;
  if( sqlite3GlobalConfig.bCoreMutex ){
    if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){
      /* 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 *pFrom = sqlite3DefaultMutex();
      sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex;






      memcpy(pTo, pFrom, offsetof(sqlite3_mutex_methods, xMutexAlloc));
      memcpy(&pTo->xMutexFree, &pFrom->xMutexFree,
             sizeof(*pTo) - offsetof(sqlite3_mutex_methods, xMutexFree));
      pTo->xMutexAlloc = pFrom->xMutexAlloc;
    }
    rc = sqlite3GlobalConfig.mutex.xMutexInit();
  }

#ifdef SQLITE_DEBUG
  GLOBAL(int, mutexIsInit) = 1;
#endif

  return rc;
}
................................................................................
  return rc;
}

/*
** Retrieve a pointer to a static mutex or allocate a new dynamic one.
*/
sqlite3_mutex *sqlite3_mutex_alloc(int id){
  if( !sqlite3GlobalConfig.bCoreMutex ) return 0;
#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite3_initialize() ) return 0;
#endif
  return sqlite3GlobalConfig.mutex.xMutexAlloc(id);
}

sqlite3_mutex *sqlite3MutexAlloc(int id){








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#ifndef SQLITE_MUTEX_OMIT
/*
** Initialize the mutex system.
*/
int sqlite3MutexInit(void){ 
  int rc = SQLITE_OK;

  if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){
    /* 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 *pFrom;
    sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex;

    if( sqlite3GlobalConfig.bCoreMutex ){
      pFrom = sqlite3DefaultMutex();
    }else{
      pFrom = sqlite3NoopMutex();
    }
    memcpy(pTo, pFrom, offsetof(sqlite3_mutex_methods, xMutexAlloc));
    memcpy(&pTo->xMutexFree, &pFrom->xMutexFree,
           sizeof(*pTo) - offsetof(sqlite3_mutex_methods, xMutexFree));
    pTo->xMutexAlloc = pFrom->xMutexAlloc;
  }
  rc = sqlite3GlobalConfig.mutex.xMutexInit();


#ifdef SQLITE_DEBUG
  GLOBAL(int, mutexIsInit) = 1;
#endif

  return rc;
}
................................................................................
  return rc;
}

/*
** Retrieve a pointer to a static mutex or allocate a new dynamic one.
*/
sqlite3_mutex *sqlite3_mutex_alloc(int id){

#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite3_initialize() ) return 0;
#endif
  return sqlite3GlobalConfig.mutex.xMutexAlloc(id);
}

sqlite3_mutex *sqlite3MutexAlloc(int id){

Changes to src/mutex_noop.c. 

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** If compiled with SQLITE_DEBUG, then additional logic is inserted
** that does error checking on mutexes to make sure they are being
** called correctly.
*/
#include "sqliteInt.h"


#if defined(SQLITE_MUTEX_NOOP) && !defined(SQLITE_DEBUG)
/*
** Stub routines for all mutex methods.
**
** This routines provide no mutual exclusion or error checking.
*/
static int noopMutexHeld(sqlite3_mutex *p){ return 1; }
static int noopMutexNotheld(sqlite3_mutex *p){ return 1; }
................................................................................
static int noopMutexEnd(void){ return SQLITE_OK; }
static sqlite3_mutex *noopMutexAlloc(int id){ return (sqlite3_mutex*)8; }
static void noopMutexFree(sqlite3_mutex *p){ return; }
static void noopMutexEnter(sqlite3_mutex *p){ return; }
static int noopMutexTry(sqlite3_mutex *p){ return SQLITE_OK; }
static void noopMutexLeave(sqlite3_mutex *p){ return; }

sqlite3_mutex_methods *sqlite3DefaultMutex(void){
  static sqlite3_mutex_methods sMutex = {
    noopMutexInit,
    noopMutexEnd,
    noopMutexAlloc,
    noopMutexFree,
    noopMutexEnter,
    noopMutexTry,
................................................................................

    noopMutexHeld,
    noopMutexNotheld
  };

  return &sMutex;
}
#endif /* defined(SQLITE_MUTEX_NOOP) && !defined(SQLITE_DEBUG) */

#if defined(SQLITE_MUTEX_NOOP) && defined(SQLITE_DEBUG)
/*
** In this implementation, error checking is provided for testing
** and debugging purposes.  The mutexes still do not provide any
** mutual exclusion.
*/

/*
................................................................................
*/
static void debugMutexLeave(sqlite3_mutex *p){
  assert( debugMutexHeld(p) );
  p->cnt--;
  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(p) );
}

sqlite3_mutex_methods *sqlite3DefaultMutex(void){
  static sqlite3_mutex_methods sMutex = {
    debugMutexInit,
    debugMutexEnd,
    debugMutexAlloc,
    debugMutexFree,
    debugMutexEnter,
    debugMutexTry,
................................................................................

    debugMutexHeld,
    debugMutexNotheld
  };

  return &sMutex;
}






#endif /* defined(SQLITE_MUTEX_NOOP) && defined(SQLITE_DEBUG) */












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** If compiled with SQLITE_DEBUG, then additional logic is inserted
** that does error checking on mutexes to make sure they are being
** called correctly.
*/
#include "sqliteInt.h"


#ifndef SQLITE_DEBUG
/*
** Stub routines for all mutex methods.
**
** This routines provide no mutual exclusion or error checking.
*/
static int noopMutexHeld(sqlite3_mutex *p){ return 1; }
static int noopMutexNotheld(sqlite3_mutex *p){ return 1; }
................................................................................
static int noopMutexEnd(void){ return SQLITE_OK; }
static sqlite3_mutex *noopMutexAlloc(int id){ return (sqlite3_mutex*)8; }
static void noopMutexFree(sqlite3_mutex *p){ return; }
static void noopMutexEnter(sqlite3_mutex *p){ return; }
static int noopMutexTry(sqlite3_mutex *p){ return SQLITE_OK; }
static void noopMutexLeave(sqlite3_mutex *p){ return; }

sqlite3_mutex_methods *sqlite3NoopMutex(void){
  static sqlite3_mutex_methods sMutex = {
    noopMutexInit,
    noopMutexEnd,
    noopMutexAlloc,
    noopMutexFree,
    noopMutexEnter,
    noopMutexTry,
................................................................................

    noopMutexHeld,
    noopMutexNotheld
  };

  return &sMutex;
}
#endif /* !SQLITE_DEBUG */

#ifdef SQLITE_DEBUG
/*
** In this implementation, error checking is provided for testing
** and debugging purposes.  The mutexes still do not provide any
** mutual exclusion.
*/

/*
................................................................................
*/
static void debugMutexLeave(sqlite3_mutex *p){
  assert( debugMutexHeld(p) );
  p->cnt--;
  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(p) );
}

sqlite3_mutex_methods *sqlite3NoopMutex(void){
  static sqlite3_mutex_methods sMutex = {
    debugMutexInit,
    debugMutexEnd,
    debugMutexAlloc,
    debugMutexFree,
    debugMutexEnter,
    debugMutexTry,
................................................................................

    debugMutexHeld,
    debugMutexNotheld
  };

  return &sMutex;
}
#endif /* SQLITE_DEBUG */

/*
** If compiled with SQLITE_MUTEX_NOOP, then the no-op mutex implementation
** is used regardless of the run-time threadsafety setting.
*/
#ifdef SQLITE_MUTEX_NOOP
sqlite3_mutex_methods *sqlite3DefaultMutex(void){
  return sqliteNoopMutex();
}
#endif /* SQLITE_MUTEX_NOOP */

Changes to src/sqliteInt.h. 

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#ifdef SQLITE_ENABLE_MEMSYS5
const sqlite3_mem_methods *sqlite3MemGetMemsys5(void);
#endif


#ifndef SQLITE_MUTEX_OMIT
  sqlite3_mutex_methods *sqlite3DefaultMutex(void);

  sqlite3_mutex *sqlite3MutexAlloc(int);
  int sqlite3MutexInit(void);
  int sqlite3MutexEnd(void);
#endif

int sqlite3StatusValue(int);
void sqlite3StatusAdd(int, int);








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#ifdef SQLITE_ENABLE_MEMSYS5
const sqlite3_mem_methods *sqlite3MemGetMemsys5(void);
#endif


#ifndef SQLITE_MUTEX_OMIT
  sqlite3_mutex_methods *sqlite3DefaultMutex(void);
  sqlite3_mutex_methods *sqlite3NoopMutex(void);
  sqlite3_mutex *sqlite3MutexAlloc(int);
  int sqlite3MutexInit(void);
  int sqlite3MutexEnd(void);
#endif

int sqlite3StatusValue(int);
void sqlite3StatusAdd(int, int);

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