src/malloc.c

   1 /*
   2 ** 2001 September 15
   3 **
   4 ** The author disclaims copyright to this source code.  In place of
   5 ** a legal notice, here is a blessing:
   6 **
   7 **    May you do good and not evil.
   8 **    May you find forgiveness for yourself and forgive others.
   9 **    May you share freely, never taking more than you give.
  10 **
  11 *************************************************************************
  12 **
  13 ** Memory allocation functions used throughout sqlite.
  14 */
  15 #include "sqliteInt.h"
  16 #include <stdarg.h>
  17
  18 /*
  19 ** Attempt to release up to n bytes of non-essential memory currently
  20 ** held by SQLite. An example of non-essential memory is memory used to
  21 ** cache database pages that are not currently in use.
  22 */
  23 int sqlite3_release_memory(int n){
  24 #ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
  25   return sqlite3PcacheReleaseMemory(n);
  26 #else
  27   /* IMPLEMENTATION-OF: R-34391-24921 The sqlite3_release_memory() routine
  28   ** is a no-op returning zero if SQLite is not compiled with
  29   ** SQLITE_ENABLE_MEMORY_MANAGEMENT. */
  30   UNUSED_PARAMETER(n);
  31   return 0;
  32 #endif
  33 }
  34
  35 /*
  36 ** An instance of the following object records the location of
  37 ** each unused scratch buffer.
  38 */
  39 typedef struct ScratchFreeslot {
  40   struct ScratchFreeslot *pNext;   /* Next unused scratch buffer */
  41 } ScratchFreeslot;
  42
  43 /*
  44 ** State information local to the memory allocation subsystem.
  45 */
  46 static SQLITE_WSD struct Mem0Global {
  47   sqlite3_mutex *mutex;         /* Mutex to serialize access */
  48   sqlite3_int64 alarmThreshold; /* The soft heap limit */
  49
  50   /*
  51   ** Pointers to the end of sqlite3GlobalConfig.pScratch memory
  52   ** (so that a range test can be used to determine if an allocation
  53   ** being freed came from pScratch) and a pointer to the list of
  54   ** unused scratch allocations.
  55   */
  56   void *pScratchEnd;
  57   ScratchFreeslot *pScratchFree;
  58   u32 nScratchFree;
  59
  60   /*
  61   ** True if heap is nearly "full" where "full" is defined by the
  62   ** sqlite3_soft_heap_limit() setting.
  63   */
  64   int nearlyFull;
  65 } mem0 = { 0, 0, 0, 0, 0, 0 };
  66
  67 #define mem0 GLOBAL(struct Mem0Global, mem0)
  68
  69 /*
  70 ** Return the memory allocator mutex. sqlite3_status() needs it.
  71 */
  72 sqlite3_mutex *sqlite3MallocMutex(void){
  73   return mem0.mutex;
  74 }
  75
  76 #ifndef SQLITE_OMIT_DEPRECATED
  77 /*
  78 ** Deprecated external interface.  It used to set an alarm callback
  79 ** that was invoked when memory usage grew too large.  Now it is a
  80 ** no-op.
  81 */
  82 int sqlite3_memory_alarm(
  83   void(*xCallback)(void *pArg, sqlite3_int64 used,int N),
  84   void *pArg,
  85   sqlite3_int64 iThreshold
  86 ){
  87   (void)xCallback;
  88   (void)pArg;
  89   (void)iThreshold;
  90   return SQLITE_OK;
  91 }
  92 #endif
  93
  94 /*
  95 ** Set the soft heap-size limit for the library. Passing a zero or
  96 ** negative value indicates no limit.
  97 */
  98 sqlite3_int64 sqlite3_soft_heap_limit64(sqlite3_int64 n){
  99   sqlite3_int64 priorLimit;
 100   sqlite3_int64 excess;
 101   sqlite3_int64 nUsed;
 102 #ifndef SQLITE_OMIT_AUTOINIT
 103   int rc = sqlite3_initialize();
 104   if( rc ) return -1;
 105 #endif
 106   sqlite3_mutex_enter(mem0.mutex);
 107   priorLimit = mem0.alarmThreshold;
 108   if( n<0 ){
 109     sqlite3_mutex_leave(mem0.mutex);
 110     return priorLimit;
 111   }
 112   mem0.alarmThreshold = n;
 113   nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
 114   mem0.nearlyFull = (n>0 && n<=nUsed);
 115   sqlite3_mutex_leave(mem0.mutex);
 116   excess = sqlite3_memory_used() - n;
 117   if( excess>0 ) sqlite3_release_memory((int)(excess & 0x7fffffff));
 118   return priorLimit;
 119 }
 120 void sqlite3_soft_heap_limit(int n){
 121   if( n<0 ) n = 0;
 122   sqlite3_soft_heap_limit64(n);
 123 }
 124
 125 /*
 126 ** Initialize the memory allocation subsystem.
 127 */
 128 int sqlite3MallocInit(void){
 129   int rc;
 130   if( sqlite3GlobalConfig.m.xMalloc==0 ){
 131     sqlite3MemSetDefault();
 132   }
 133   memset(&mem0, 0, sizeof(mem0));
 134   mem0.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
 135   if( sqlite3GlobalConfig.pScratch && sqlite3GlobalConfig.szScratch>=100
 136       && sqlite3GlobalConfig.nScratch>0 ){
 137     int i, n, sz;
 138     ScratchFreeslot *pSlot;
 139     sz = ROUNDDOWN8(sqlite3GlobalConfig.szScratch);
 140     sqlite3GlobalConfig.szScratch = sz;
 141     pSlot = (ScratchFreeslot*)sqlite3GlobalConfig.pScratch;
 142     n = sqlite3GlobalConfig.nScratch;
 143     mem0.pScratchFree = pSlot;
 144     mem0.nScratchFree = n;
 145     for(i=0; i<n-1; i++){
 146       pSlot->pNext = (ScratchFreeslot*)(sz+(char*)pSlot);
 147       pSlot = pSlot->pNext;
 148     }
 149     pSlot->pNext = 0;
 150     mem0.pScratchEnd = (void*)&pSlot[1];
 151   }else{
 152     mem0.pScratchEnd = 0;
 153     sqlite3GlobalConfig.pScratch = 0;
 154     sqlite3GlobalConfig.szScratch = 0;
 155     sqlite3GlobalConfig.nScratch = 0;
 156   }
 157   if( sqlite3GlobalConfig.pPage==0 || sqlite3GlobalConfig.szPage<512
 158       || sqlite3GlobalConfig.nPage<=0 ){
 159     sqlite3GlobalConfig.pPage = 0;
 160     sqlite3GlobalConfig.szPage = 0;
 161   }
 162   rc = sqlite3GlobalConfig.m.xInit(sqlite3GlobalConfig.m.pAppData);
 163   if( rc!=SQLITE_OK ) memset(&mem0, 0, sizeof(mem0));
 164   return rc;
 165 }
 166
 167 /*
 168 ** Return true if the heap is currently under memory pressure - in other
 169 ** words if the amount of heap used is close to the limit set by
 170 ** sqlite3_soft_heap_limit().
 171 */
 172 int sqlite3HeapNearlyFull(void){
 173   return mem0.nearlyFull;
 174 }
 175
 176 /*
 177 ** Deinitialize the memory allocation subsystem.
 178 */
 179 void sqlite3MallocEnd(void){
 180   if( sqlite3GlobalConfig.m.xShutdown ){
 181     sqlite3GlobalConfig.m.xShutdown(sqlite3GlobalConfig.m.pAppData);
 182   }
 183   memset(&mem0, 0, sizeof(mem0));
 184 }
 185
 186 /*
 187 ** Return the amount of memory currently checked out.
 188 */
 189 sqlite3_int64 sqlite3_memory_used(void){
 190   sqlite3_int64 res, mx;
 191   sqlite3_status64(SQLITE_STATUS_MEMORY_USED, &res, &mx, 0);
 192   return res;
 193 }
 194
 195 /*
 196 ** Return the maximum amount of memory that has ever been
 197 ** checked out since either the beginning of this process
 198 ** or since the most recent reset.
 199 */
 200 sqlite3_int64 sqlite3_memory_highwater(int resetFlag){
 201   sqlite3_int64 res, mx;
 202   sqlite3_status64(SQLITE_STATUS_MEMORY_USED, &res, &mx, resetFlag);
 203   return mx;
 204 }
 205
 206 /*
 207 ** Trigger the alarm
 208 */
 209 static void sqlite3MallocAlarm(int nByte){
 210   if( mem0.alarmThreshold<=0 ) return;
 211   sqlite3_mutex_leave(mem0.mutex);
 212   sqlite3_release_memory(nByte);
 213   sqlite3_mutex_enter(mem0.mutex);
 214 }
 215
 216 /*
 217 ** Do a memory allocation with statistics and alarms.  Assume the
 218 ** lock is already held.
 219 */
 220 static int mallocWithAlarm(int n, void **pp){
 221   int nFull;
 222   void *p;
 223   assert( sqlite3_mutex_held(mem0.mutex) );
 224   nFull = sqlite3GlobalConfig.m.xRoundup(n);
 225   sqlite3StatusHighwater(SQLITE_STATUS_MALLOC_SIZE, n);
 226   if( mem0.alarmThreshold>0 ){
 227     sqlite3_int64 nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
 228     if( nUsed >= mem0.alarmThreshold - nFull ){
 229       mem0.nearlyFull = 1;
 230       sqlite3MallocAlarm(nFull);
 231     }else{
 232       mem0.nearlyFull = 0;
 233     }
 234   }
 235   p = sqlite3GlobalConfig.m.xMalloc(nFull);
 236 #ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
 237   if( p==0 && mem0.alarmThreshold>0 ){
 238     sqlite3MallocAlarm(nFull);
 239     p = sqlite3GlobalConfig.m.xMalloc(nFull);
 240   }
 241 #endif
 242   if( p ){
 243     nFull = sqlite3MallocSize(p);
 244     sqlite3StatusUp(SQLITE_STATUS_MEMORY_USED, nFull);
 245     sqlite3StatusUp(SQLITE_STATUS_MALLOC_COUNT, 1);
 246   }
 247   *pp = p;
 248   return nFull;
 249 }
 250
 251 /*
 252 ** Allocate memory.  This routine is like sqlite3_malloc() except that it
 253 ** assumes the memory subsystem has already been initialized.
 254 */
 255 void *sqlite3Malloc(u64 n){
 256   void *p;
 257   if( n==0 || n>=0x7fffff00 ){
 258     /* A memory allocation of a number of bytes which is near the maximum
 259     ** signed integer value might cause an integer overflow inside of the
 260     ** xMalloc().  Hence we limit the maximum size to 0x7fffff00, giving
 261     ** 255 bytes of overhead.  SQLite itself will never use anything near
 262     ** this amount.  The only way to reach the limit is with sqlite3_malloc() */
 263     p = 0;
 264   }else if( sqlite3GlobalConfig.bMemstat ){
 265     sqlite3_mutex_enter(mem0.mutex);
 266     mallocWithAlarm((int)n, &p);
 267     sqlite3_mutex_leave(mem0.mutex);
 268   }else{
 269     p = sqlite3GlobalConfig.m.xMalloc((int)n);
 270   }
 271   assert( EIGHT_BYTE_ALIGNMENT(p) );  /* IMP: R-11148-40995 */
 272   return p;
 273 }
 274
 275 /*
 276 ** This version of the memory allocation is for use by the application.
 277 ** First make sure the memory subsystem is initialized, then do the
 278 ** allocation.
 279 */
 280 void *sqlite3_malloc(int n){
 281 #ifndef SQLITE_OMIT_AUTOINIT
 282   if( sqlite3_initialize() ) return 0;
 283 #endif
 284   return n<=0 ? 0 : sqlite3Malloc(n);
 285 }
 286 void *sqlite3_malloc64(sqlite3_uint64 n){
 287 #ifndef SQLITE_OMIT_AUTOINIT
 288   if( sqlite3_initialize() ) return 0;
 289 #endif
 290   return sqlite3Malloc(n);
 291 }
 292
 293 /*
 294 ** Each thread may only have a single outstanding allocation from
 295 ** xScratchMalloc().  We verify this constraint in the single-threaded
 296 ** case by setting scratchAllocOut to 1 when an allocation
 297 ** is outstanding clearing it when the allocation is freed.
 298 */
 299 #if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
 300 static int scratchAllocOut = 0;
 301 #endif
 302
 303
 304 /*
 305 ** Allocate memory that is to be used and released right away.
 306 ** This routine is similar to alloca() in that it is not intended
 307 ** for situations where the memory might be held long-term.  This
 308 ** routine is intended to get memory to old large transient data
 309 ** structures that would not normally fit on the stack of an
 310 ** embedded processor.
 311 */
 312 void *sqlite3ScratchMalloc(int n){
 313   void *p;
 314   assert( n>0 );
 315
 316   sqlite3_mutex_enter(mem0.mutex);
 317   sqlite3StatusHighwater(SQLITE_STATUS_SCRATCH_SIZE, n);
 318   if( mem0.nScratchFree && sqlite3GlobalConfig.szScratch>=n ){
 319     p = mem0.pScratchFree;
 320     mem0.pScratchFree = mem0.pScratchFree->pNext;
 321     mem0.nScratchFree--;
 322     sqlite3StatusUp(SQLITE_STATUS_SCRATCH_USED, 1);
 323     sqlite3_mutex_leave(mem0.mutex);
 324   }else{
 325     sqlite3_mutex_leave(mem0.mutex);
 326     p = sqlite3Malloc(n);
 327     if( sqlite3GlobalConfig.bMemstat && p ){
 328       sqlite3_mutex_enter(mem0.mutex);
 329       sqlite3StatusUp(SQLITE_STATUS_SCRATCH_OVERFLOW, sqlite3MallocSize(p));
 330       sqlite3_mutex_leave(mem0.mutex);
 331     }
 332     sqlite3MemdebugSetType(p, MEMTYPE_SCRATCH);
 333   }
 334   assert( sqlite3_mutex_notheld(mem0.mutex) );
 335
 336
 337 #if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
 338   /* EVIDENCE-OF: R-12970-05880 SQLite will not use more than one scratch
 339   ** buffers per thread.
 340   **
 341   ** This can only be checked in single-threaded mode.
 342   */
 343   assert( scratchAllocOut==0 );
 344   if( p ) scratchAllocOut++;
 345 #endif
 346
 347   return p;
 348 }
 349 void sqlite3ScratchFree(void *p){
 350   if( p ){
 351
 352 #if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
 353     /* Verify that no more than two scratch allocation per thread
 354     ** is outstanding at one time.  (This is only checked in the
 355     ** single-threaded case since checking in the multi-threaded case
 356     ** would be much more complicated.) */
 357     assert( scratchAllocOut>=1 && scratchAllocOut<=2 );
 358     scratchAllocOut--;
 359 #endif
 360
 361     if( SQLITE_WITHIN(p, sqlite3GlobalConfig.pScratch, mem0.pScratchEnd) ){
 362       /* Release memory from the SQLITE_CONFIG_SCRATCH allocation */
 363       ScratchFreeslot *pSlot;
 364       pSlot = (ScratchFreeslot*)p;
 365       sqlite3_mutex_enter(mem0.mutex);
 366       pSlot->pNext = mem0.pScratchFree;
 367       mem0.pScratchFree = pSlot;
 368       mem0.nScratchFree++;
 369       assert( mem0.nScratchFree <= (u32)sqlite3GlobalConfig.nScratch );
 370       sqlite3StatusDown(SQLITE_STATUS_SCRATCH_USED, 1);
 371       sqlite3_mutex_leave(mem0.mutex);
 372     }else{
 373       /* Release memory back to the heap */
 374       assert( sqlite3MemdebugHasType(p, MEMTYPE_SCRATCH) );
 375       assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_SCRATCH) );
 376       sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
 377       if( sqlite3GlobalConfig.bMemstat ){
 378         int iSize = sqlite3MallocSize(p);
 379         sqlite3_mutex_enter(mem0.mutex);
 380         sqlite3StatusDown(SQLITE_STATUS_SCRATCH_OVERFLOW, iSize);
 381         sqlite3StatusDown(SQLITE_STATUS_MEMORY_USED, iSize);
 382         sqlite3StatusDown(SQLITE_STATUS_MALLOC_COUNT, 1);
 383         sqlite3GlobalConfig.m.xFree(p);
 384         sqlite3_mutex_leave(mem0.mutex);
 385       }else{
 386         sqlite3GlobalConfig.m.xFree(p);
 387       }
 388     }
 389   }
 390 }
 391
 392 /*
 393 ** TRUE if p is a lookaside memory allocation from db
 394 */
 395 #ifndef SQLITE_OMIT_LOOKASIDE
 396 static int isLookaside(sqlite3 *db, void *p){
 397   return SQLITE_WITHIN(p, db->lookaside.pStart, db->lookaside.pEnd);
 398 }
 399 #else
 400 #define isLookaside(A,B) 0
 401 #endif
 402
 403 /*
 404 ** Return the size of a memory allocation previously obtained from
 405 ** sqlite3Malloc() or sqlite3_malloc().
 406 */
 407 int sqlite3MallocSize(void *p){
 408   assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
 409   return sqlite3GlobalConfig.m.xSize(p);
 410 }
 411 int sqlite3DbMallocSize(sqlite3 *db, void *p){
 412   assert( p!=0 );
 413   if( db==0 || !isLookaside(db,p) ){
 414 #if SQLITE_DEBUG
 415     if( db==0 ){
 416       assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_HEAP) );
 417       assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
 418     }else{
 419       assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
 420       assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
 421     }
 422 #endif
 423     return sqlite3GlobalConfig.m.xSize(p);
 424   }else{
 425     assert( sqlite3_mutex_held(db->mutex) );
 426     return db->lookaside.sz;
 427   }
 428 }
 429 sqlite3_uint64 sqlite3_msize(void *p){
 430   assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_HEAP) );
 431   assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
 432   return p ? sqlite3GlobalConfig.m.xSize(p) : 0;
 433 }
 434
 435 /*
 436 ** Free memory previously obtained from sqlite3Malloc().
 437 */
 438 void sqlite3_free(void *p){
 439   if( p==0 ) return;  /* IMP: R-49053-54554 */
 440   assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
 441   assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_HEAP) );
 442   if( sqlite3GlobalConfig.bMemstat ){
 443     sqlite3_mutex_enter(mem0.mutex);
 444     sqlite3StatusDown(SQLITE_STATUS_MEMORY_USED, sqlite3MallocSize(p));
 445     sqlite3StatusDown(SQLITE_STATUS_MALLOC_COUNT, 1);
 446     sqlite3GlobalConfig.m.xFree(p);
 447     sqlite3_mutex_leave(mem0.mutex);
 448   }else{
 449     sqlite3GlobalConfig.m.xFree(p);
 450   }
 451 }
 452
 453 /*
 454 ** Add the size of memory allocation "p" to the count in
 455 ** *db->pnBytesFreed.
 456 */
 457 static SQLITE_NOINLINE void measureAllocationSize(sqlite3 *db, void *p){
 458   *db->pnBytesFreed += sqlite3DbMallocSize(db,p);
 459 }
 460
 461 /*
 462 ** Free memory that might be associated with a particular database
 463 ** connection.
 464 */
 465 void sqlite3DbFree(sqlite3 *db, void *p){
 466   assert( db==0 || sqlite3_mutex_held(db->mutex) );
 467   if( p==0 ) return;
 468   if( db ){
 469     if( db->pnBytesFreed ){
 470       measureAllocationSize(db, p);
 471       return;
 472     }
 473     if( isLookaside(db, p) ){
 474       LookasideSlot *pBuf = (LookasideSlot*)p;
 475 #if SQLITE_DEBUG
 476       /* Trash all content in the buffer being freed */
 477       memset(p, 0xaa, db->lookaside.sz);
 478 #endif
 479       pBuf->pNext = db->lookaside.pFree;
 480       db->lookaside.pFree = pBuf;
 481       db->lookaside.nOut--;
 482       return;
 483     }
 484   }
 485   assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
 486   assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
 487   assert( db!=0 || sqlite3MemdebugNoType(p, MEMTYPE_LOOKASIDE) );
 488   sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
 489   sqlite3_free(p);
 490 }
 491
 492 /*
 493 ** Change the size of an existing memory allocation
 494 */
 495 void *sqlite3Realloc(void *pOld, u64 nBytes){
 496   int nOld, nNew, nDiff;
 497   void *pNew;
 498   assert( sqlite3MemdebugHasType(pOld, MEMTYPE_HEAP) );
 499   assert( sqlite3MemdebugNoType(pOld, (u8)~MEMTYPE_HEAP) );
 500   if( pOld==0 ){
 501     return sqlite3Malloc(nBytes); /* IMP: R-04300-56712 */
 502   }
 503   if( nBytes==0 ){
 504     sqlite3_free(pOld); /* IMP: R-26507-47431 */
 505     return 0;
 506   }
 507   if( nBytes>=0x7fffff00 ){
 508     /* The 0x7ffff00 limit term is explained in comments on sqlite3Malloc() */
 509     return 0;
 510   }
 511   nOld = sqlite3MallocSize(pOld);
 512   /* IMPLEMENTATION-OF: R-46199-30249 SQLite guarantees that the second
 513   ** argument to xRealloc is always a value returned by a prior call to
 514   ** xRoundup. */
 515   nNew = sqlite3GlobalConfig.m.xRoundup((int)nBytes);
 516   if( nOld==nNew ){
 517     pNew = pOld;
 518   }else if( sqlite3GlobalConfig.bMemstat ){
 519     sqlite3_mutex_enter(mem0.mutex);
 520     sqlite3StatusHighwater(SQLITE_STATUS_MALLOC_SIZE, (int)nBytes);
 521     nDiff = nNew - nOld;
 522     if( sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED) >=
 523           mem0.alarmThreshold-nDiff ){
 524       sqlite3MallocAlarm(nDiff);
 525     }
 526     pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
 527     if( pNew==0 && mem0.alarmThreshold>0 ){
 528       sqlite3MallocAlarm((int)nBytes);
 529       pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
 530     }
 531     if( pNew ){
 532       nNew = sqlite3MallocSize(pNew);
 533       sqlite3StatusUp(SQLITE_STATUS_MEMORY_USED, nNew-nOld);
 534     }
 535     sqlite3_mutex_leave(mem0.mutex);
 536   }else{
 537     pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
 538   }
 539   assert( EIGHT_BYTE_ALIGNMENT(pNew) ); /* IMP: R-11148-40995 */
 540   return pNew;
 541 }
 542
 543 /*
 544 ** The public interface to sqlite3Realloc.  Make sure that the memory
 545 ** subsystem is initialized prior to invoking sqliteRealloc.
 546 */
 547 void *sqlite3_realloc(void *pOld, int n){
 548 #ifndef SQLITE_OMIT_AUTOINIT
 549   if( sqlite3_initialize() ) return 0;
 550 #endif
 551   if( n<0 ) n = 0;  /* IMP: R-26507-47431 */
 552   return sqlite3Realloc(pOld, n);
 553 }
 554 void *sqlite3_realloc64(void *pOld, sqlite3_uint64 n){
 555 #ifndef SQLITE_OMIT_AUTOINIT
 556   if( sqlite3_initialize() ) return 0;
 557 #endif
 558   return sqlite3Realloc(pOld, n);
 559 }
 560
 561
 562 /*
 563 ** Allocate and zero memory.
 564 */
 565 void *sqlite3MallocZero(u64 n){
 566   void *p = sqlite3Malloc(n);
 567   if( p ){
 568     memset(p, 0, (size_t)n);
 569   }
 570   return p;
 571 }
 572
 573 /*
 574 ** Allocate and zero memory.  If the allocation fails, make
 575 ** the mallocFailed flag in the connection pointer.
 576 */
 577 void *sqlite3DbMallocZero(sqlite3 *db, u64 n){
 578   void *p;
 579   testcase( db==0 );
 580   p = sqlite3DbMallocRaw(db, n);
 581   if( p ) memset(p, 0, (size_t)n);
 582   return p;
 583 }
 584
 585
 586 /* Finish the work of sqlite3DbMallocRawNN for the unusual and
 587 ** slower case when the allocation cannot be fulfilled using lookaside.
 588 */
 589 static SQLITE_NOINLINE void *dbMallocRawFinish(sqlite3 *db, u64 n){
 590   void *p;
 591   assert( db!=0 );
 592   p = sqlite3Malloc(n);
 593   if( !p ) sqlite3OomFault(db);
 594   sqlite3MemdebugSetType(p,
 595          (db->lookaside.bDisable==0) ? MEMTYPE_LOOKASIDE : MEMTYPE_HEAP);
 596   return p;
 597 }
 598
 599 /*
 600 ** Allocate memory, either lookaside (if possible) or heap.
 601 ** If the allocation fails, set the mallocFailed flag in
 602 ** the connection pointer.
 603 **
 604 ** If db!=0 and db->mallocFailed is true (indicating a prior malloc
 605 ** failure on the same database connection) then always return 0.
 606 ** Hence for a particular database connection, once malloc starts
 607 ** failing, it fails consistently until mallocFailed is reset.
 608 ** This is an important assumption.  There are many places in the
 609 ** code that do things like this:
 610 **
 611 **         int *a = (int*)sqlite3DbMallocRaw(db, 100);
 612 **         int *b = (int*)sqlite3DbMallocRaw(db, 200);
 613 **         if( b ) a[10] = 9;
 614 **
 615 ** In other words, if a subsequent malloc (ex: "b") worked, it is assumed
 616 ** that all prior mallocs (ex: "a") worked too.
 617 **
 618 ** The sqlite3MallocRawNN() variant guarantees that the "db" parameter is
 619 ** not a NULL pointer.
 620 */
 621 void *sqlite3DbMallocRaw(sqlite3 *db, u64 n){
 622   void *p;
 623   if( db ) return sqlite3DbMallocRawNN(db, n);
 624   p = sqlite3Malloc(n);
 625   sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
 626   return p;
 627 }
 628 void *sqlite3DbMallocRawNN(sqlite3 *db, u64 n){
 629 #ifndef SQLITE_OMIT_LOOKASIDE
 630   LookasideSlot *pBuf;
 631   assert( db!=0 );
 632   assert( sqlite3_mutex_held(db->mutex) );
 633   assert( db->pnBytesFreed==0 );
 634   if( db->lookaside.bDisable==0 ){
 635     assert( db->mallocFailed==0 );
 636     if( n>db->lookaside.sz ){
 637       db->lookaside.anStat[1]++;
 638     }else if( (pBuf = db->lookaside.pFree)==0 ){
 639       db->lookaside.anStat[2]++;
 640     }else{
 641       db->lookaside.pFree = pBuf->pNext;
 642       db->lookaside.nOut++;
 643       db->lookaside.anStat[0]++;
 644       if( db->lookaside.nOut>db->lookaside.mxOut ){
 645         db->lookaside.mxOut = db->lookaside.nOut;
 646       }
 647       return (void*)pBuf;
 648     }
 649   }else if( db->mallocFailed ){
 650     return 0;
 651   }
 652 #else
 653   assert( db!=0 );
 654   assert( sqlite3_mutex_held(db->mutex) );
 655   assert( db->pnBytesFreed==0 );
 656   if( db->mallocFailed ){
 657     return 0;
 658   }
 659 #endif
 660   return dbMallocRawFinish(db, n);
 661 }
 662
 663 /* Forward declaration */
 664 static SQLITE_NOINLINE void *dbReallocFinish(sqlite3 *db, void *p, u64 n);
 665
 666 /*
 667 ** Resize the block of memory pointed to by p to n bytes. If the
 668 ** resize fails, set the mallocFailed flag in the connection object.
 669 */
 670 void *sqlite3DbRealloc(sqlite3 *db, void *p, u64 n){
 671   assert( db!=0 );
 672   if( p==0 ) return sqlite3DbMallocRawNN(db, n);
 673   assert( sqlite3_mutex_held(db->mutex) );
 674   if( isLookaside(db,p) && n<=db->lookaside.sz ) return p;
 675   return dbReallocFinish(db, p, n);
 676 }
 677 static SQLITE_NOINLINE void *dbReallocFinish(sqlite3 *db, void *p, u64 n){
 678   void *pNew = 0;
 679   assert( db!=0 );
 680   assert( p!=0 );
 681   if( db->mallocFailed==0 ){
 682     if( isLookaside(db, p) ){
 683       pNew = sqlite3DbMallocRawNN(db, n);
 684       if( pNew ){
 685         memcpy(pNew, p, db->lookaside.sz);
 686         sqlite3DbFree(db, p);
 687       }
 688     }else{
 689       assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
 690       assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
 691       sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
 692       pNew = sqlite3_realloc64(p, n);
 693       if( !pNew ){
 694         sqlite3OomFault(db);
 695       }
 696       sqlite3MemdebugSetType(pNew,
 697             (db->lookaside.bDisable==0 ? MEMTYPE_LOOKASIDE : MEMTYPE_HEAP));
 698     }
 699   }
 700   return pNew;
 701 }
 702
 703 /*
 704 ** Attempt to reallocate p.  If the reallocation fails, then free p
 705 ** and set the mallocFailed flag in the database connection.
 706 */
 707 void *sqlite3DbReallocOrFree(sqlite3 *db, void *p, u64 n){
 708   void *pNew;
 709   pNew = sqlite3DbRealloc(db, p, n);
 710   if( !pNew ){
 711     sqlite3DbFree(db, p);
 712   }
 713   return pNew;
 714 }
 715
 716 /*
 717 ** Make a copy of a string in memory obtained from sqliteMalloc(). These
 718 ** functions call sqlite3MallocRaw() directly instead of sqliteMalloc(). This
 719 ** is because when memory debugging is turned on, these two functions are
 720 ** called via macros that record the current file and line number in the
 721 ** ThreadData structure.
 722 */
 723 char *sqlite3DbStrDup(sqlite3 *db, const char *z){
 724   char *zNew;
 725   size_t n;
 726   if( z==0 ){
 727     return 0;
 728   }
 729   n = sqlite3Strlen30(z) + 1;
 730   assert( (n&0x7fffffff)==n );
 731   zNew = sqlite3DbMallocRaw(db, (int)n);
 732   if( zNew ){
 733     memcpy(zNew, z, n);
 734   }
 735   return zNew;
 736 }
 737 char *sqlite3DbStrNDup(sqlite3 *db, const char *z, u64 n){
 738   char *zNew;
 739   assert( db!=0 );
 740   if( z==0 ){
 741     return 0;
 742   }
 743   assert( (n&0x7fffffff)==n );
 744   zNew = sqlite3DbMallocRawNN(db, n+1);
 745   if( zNew ){
 746     memcpy(zNew, z, (size_t)n);
 747     zNew[n] = 0;
 748   }
 749   return zNew;
 750 }
 751
 752 /*
 753 ** Free any prior content in *pz and replace it with a copy of zNew.
 754 */
 755 void sqlite3SetString(char **pz, sqlite3 *db, const char *zNew){
 756   sqlite3DbFree(db, *pz);
 757   *pz = sqlite3DbStrDup(db, zNew);
 758 }
 759
 760 /*
 761 ** Call this routine to record the fact that an OOM (out-of-memory) error
 762 ** has happened.  This routine will set db->mallocFailed, and also
 763 ** temporarily disable the lookaside memory allocator and interrupt
 764 ** any running VDBEs.
 765 */
 766 void sqlite3OomFault(sqlite3 *db){
 767   if( db->mallocFailed==0 && db->bBenignMalloc==0 ){
 768     db->mallocFailed = 1;
 769     if( db->nVdbeExec>0 ){
 770       db->u1.isInterrupted = 1;
 771     }
 772     db->lookaside.bDisable++;
 773   }
 774 }
 775
 776 /*
 777 ** This routine reactivates the memory allocator and clears the
 778 ** db->mallocFailed flag as necessary.
 779 **
 780 ** The memory allocator is not restarted if there are running
 781 ** VDBEs.
 782 */
 783 void sqlite3OomClear(sqlite3 *db){
 784   if( db->mallocFailed && db->nVdbeExec==0 ){
 785     db->mallocFailed = 0;
 786     db->u1.isInterrupted = 0;
 787     assert( db->lookaside.bDisable>0 );
 788     db->lookaside.bDisable--;
 789   }
 790 }
 791
 792 /*
 793 ** Take actions at the end of an API call to indicate an OOM error
 794 */
 795 static SQLITE_NOINLINE int apiOomError(sqlite3 *db){
 796   sqlite3OomClear(db);
 797   sqlite3Error(db, SQLITE_NOMEM);
 798   return SQLITE_NOMEM_BKPT;
 799 }
 800
 801 /*
 802 ** This function must be called before exiting any API function (i.e.
 803 ** returning control to the user) that has called sqlite3_malloc or
 804 ** sqlite3_realloc.
 805 **
 806 ** The returned value is normally a copy of the second argument to this
 807 ** function. However, if a malloc() failure has occurred since the previous
 808 ** invocation SQLITE_NOMEM is returned instead.
 809 **
 810 ** If an OOM as occurred, then the connection error-code (the value
 811 ** returned by sqlite3_errcode()) is set to SQLITE_NOMEM.
 812 */
 813 int sqlite3ApiExit(sqlite3* db, int rc){
 814   /* If the db handle must hold the connection handle mutex here.
 815   ** Otherwise the read (and possible write) of db->mallocFailed
 816   ** is unsafe, as is the call to sqlite3Error().
 817   */
 818   assert( db!=0 );
 819   assert( sqlite3_mutex_held(db->mutex) );
 820   if( db->mallocFailed || rc==SQLITE_IOERR_NOMEM ){
 821     return apiOomError(db);
 822   }
 823   return rc & db->errMask;
 824 }