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 ** State information local to the memory allocation subsystem.
  37 */
  38 static SQLITE_WSD struct Mem0Global {
  39   sqlite3_mutex *mutex;         /* Mutex to serialize access */
  40   sqlite3_int64 alarmThreshold; /* The soft heap limit */
  41
  42   /*
  43   ** True if heap is nearly "full" where "full" is defined by the
  44   ** sqlite3_soft_heap_limit() setting.
  45   */
  46   int nearlyFull;
  47 } mem0 = { 0, 0, 0 };
  48
  49 #define mem0 GLOBAL(struct Mem0Global, mem0)
  50
  51 /*
  52 ** Return the memory allocator mutex. sqlite3_status() needs it.
  53 */
  54 sqlite3_mutex *sqlite3MallocMutex(void){
  55   return mem0.mutex;
  56 }
  57
  58 #ifndef SQLITE_OMIT_DEPRECATED
  59 /*
  60 ** Deprecated external interface.  It used to set an alarm callback
  61 ** that was invoked when memory usage grew too large.  Now it is a
  62 ** no-op.
  63 */
  64 int sqlite3_memory_alarm(
  65   void(*xCallback)(void *pArg, sqlite3_int64 used,int N),
  66   void *pArg,
  67   sqlite3_int64 iThreshold
  68 ){
  69   (void)xCallback;
  70   (void)pArg;
  71   (void)iThreshold;
  72   return SQLITE_OK;
  73 }
  74 #endif
  75
  76 /*
  77 ** Set the soft heap-size limit for the library. Passing a zero or
  78 ** negative value indicates no limit.
  79 */
  80 sqlite3_int64 sqlite3_soft_heap_limit64(sqlite3_int64 n){
  81   sqlite3_int64 priorLimit;
  82   sqlite3_int64 excess;
  83   sqlite3_int64 nUsed;
  84 #ifndef SQLITE_OMIT_AUTOINIT
  85   int rc = sqlite3_initialize();
  86   if( rc ) return -1;
  87 #endif
  88   sqlite3_mutex_enter(mem0.mutex);
  89   priorLimit = mem0.alarmThreshold;
  90   if( n<0 ){
  91     sqlite3_mutex_leave(mem0.mutex);
  92     return priorLimit;
  93   }
  94   mem0.alarmThreshold = n;
  95   nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
  96   mem0.nearlyFull = (n>0 && n<=nUsed);
  97   sqlite3_mutex_leave(mem0.mutex);
  98   excess = sqlite3_memory_used() - n;
  99   if( excess>0 ) sqlite3_release_memory((int)(excess & 0x7fffffff));
 100   return priorLimit;
 101 }
 102 void sqlite3_soft_heap_limit(int n){
 103   if( n<0 ) n = 0;
 104   sqlite3_soft_heap_limit64(n);
 105 }
 106
 107 /*
 108 ** Initialize the memory allocation subsystem.
 109 */
 110 int sqlite3MallocInit(void){
 111   int rc;
 112   if( sqlite3GlobalConfig.m.xMalloc==0 ){
 113     sqlite3MemSetDefault();
 114   }
 115   memset(&mem0, 0, sizeof(mem0));
 116   mem0.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
 117   if( sqlite3GlobalConfig.pPage==0 || sqlite3GlobalConfig.szPage<512
 118       || sqlite3GlobalConfig.nPage<=0 ){
 119     sqlite3GlobalConfig.pPage = 0;
 120     sqlite3GlobalConfig.szPage = 0;
 121   }
 122   rc = sqlite3GlobalConfig.m.xInit(sqlite3GlobalConfig.m.pAppData);
 123   if( rc!=SQLITE_OK ) memset(&mem0, 0, sizeof(mem0));
 124   return rc;
 125 }
 126
 127 /*
 128 ** Return true if the heap is currently under memory pressure - in other
 129 ** words if the amount of heap used is close to the limit set by
 130 ** sqlite3_soft_heap_limit().
 131 */
 132 int sqlite3HeapNearlyFull(void){
 133   return mem0.nearlyFull;
 134 }
 135
 136 /*
 137 ** Deinitialize the memory allocation subsystem.
 138 */
 139 void sqlite3MallocEnd(void){
 140   if( sqlite3GlobalConfig.m.xShutdown ){
 141     sqlite3GlobalConfig.m.xShutdown(sqlite3GlobalConfig.m.pAppData);
 142   }
 143   memset(&mem0, 0, sizeof(mem0));
 144 }
 145
 146 /*
 147 ** Return the amount of memory currently checked out.
 148 */
 149 sqlite3_int64 sqlite3_memory_used(void){
 150   sqlite3_int64 res, mx;
 151   sqlite3_status64(SQLITE_STATUS_MEMORY_USED, &res, &mx, 0);
 152   return res;
 153 }
 154
 155 /*
 156 ** Return the maximum amount of memory that has ever been
 157 ** checked out since either the beginning of this process
 158 ** or since the most recent reset.
 159 */
 160 sqlite3_int64 sqlite3_memory_highwater(int resetFlag){
 161   sqlite3_int64 res, mx;
 162   sqlite3_status64(SQLITE_STATUS_MEMORY_USED, &res, &mx, resetFlag);
 163   return mx;
 164 }
 165
 166 /*
 167 ** Trigger the alarm
 168 */
 169 static void sqlite3MallocAlarm(int nByte){
 170   if( mem0.alarmThreshold<=0 ) return;
 171   sqlite3_mutex_leave(mem0.mutex);
 172   sqlite3_release_memory(nByte);
 173   sqlite3_mutex_enter(mem0.mutex);
 174 }
 175
 176 /*
 177 ** Do a memory allocation with statistics and alarms.  Assume the
 178 ** lock is already held.
 179 */
 180 static void mallocWithAlarm(int n, void **pp){
 181   void *p;
 182   int nFull;
 183   assert( sqlite3_mutex_held(mem0.mutex) );
 184   assert( n>0 );
 185
 186   /* In Firefox (circa 2017-02-08), xRoundup() is remapped to an internal
 187   ** implementation of malloc_good_size(), which must be called in debug
 188   ** mode and specifically when the DMD "Dark Matter Detector" is enabled
 189   ** or else a crash results.  Hence, do not attempt to optimize out the
 190   ** following xRoundup() call. */
 191   nFull = sqlite3GlobalConfig.m.xRoundup(n);
 192
 193 #ifdef SQLITE_MAX_MEMORY
 194   if( sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED)+nFull>SQLITE_MAX_MEMORY ){
 195     *pp = 0;
 196     return;
 197   }
 198 #endif
 199
 200   sqlite3StatusHighwater(SQLITE_STATUS_MALLOC_SIZE, n);
 201   if( mem0.alarmThreshold>0 ){
 202     sqlite3_int64 nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
 203     if( nUsed >= mem0.alarmThreshold - nFull ){
 204       mem0.nearlyFull = 1;
 205       sqlite3MallocAlarm(nFull);
 206     }else{
 207       mem0.nearlyFull = 0;
 208     }
 209   }
 210   p = sqlite3GlobalConfig.m.xMalloc(nFull);
 211 #ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
 212   if( p==0 && mem0.alarmThreshold>0 ){
 213     sqlite3MallocAlarm(nFull);
 214     p = sqlite3GlobalConfig.m.xMalloc(nFull);
 215   }
 216 #endif
 217   if( p ){
 218     nFull = sqlite3MallocSize(p);
 219     sqlite3StatusUp(SQLITE_STATUS_MEMORY_USED, nFull);
 220     sqlite3StatusUp(SQLITE_STATUS_MALLOC_COUNT, 1);
 221   }
 222   *pp = p;
 223 }
 224
 225 /*
 226 ** Allocate memory.  This routine is like sqlite3_malloc() except that it
 227 ** assumes the memory subsystem has already been initialized.
 228 */
 229 void *sqlite3Malloc(u64 n){
 230   void *p;
 231   if( n==0 || n>=0x7fffff00 ){
 232     /* A memory allocation of a number of bytes which is near the maximum
 233     ** signed integer value might cause an integer overflow inside of the
 234     ** xMalloc().  Hence we limit the maximum size to 0x7fffff00, giving
 235     ** 255 bytes of overhead.  SQLite itself will never use anything near
 236     ** this amount.  The only way to reach the limit is with sqlite3_malloc() */
 237     p = 0;
 238   }else if( sqlite3GlobalConfig.bMemstat ){
 239     sqlite3_mutex_enter(mem0.mutex);
 240     mallocWithAlarm((int)n, &p);
 241     sqlite3_mutex_leave(mem0.mutex);
 242   }else{
 243     p = sqlite3GlobalConfig.m.xMalloc((int)n);
 244   }
 245   assert( EIGHT_BYTE_ALIGNMENT(p) );  /* IMP: R-11148-40995 */
 246   return p;
 247 }
 248
 249 /*
 250 ** This version of the memory allocation is for use by the application.
 251 ** First make sure the memory subsystem is initialized, then do the
 252 ** allocation.
 253 */
 254 void *sqlite3_malloc(int n){
 255 #ifndef SQLITE_OMIT_AUTOINIT
 256   if( sqlite3_initialize() ) return 0;
 257 #endif
 258   return n<=0 ? 0 : sqlite3Malloc(n);
 259 }
 260 void *sqlite3_malloc64(sqlite3_uint64 n){
 261 #ifndef SQLITE_OMIT_AUTOINIT
 262   if( sqlite3_initialize() ) return 0;
 263 #endif
 264   return sqlite3Malloc(n);
 265 }
 266
 267 /*
 268 ** TRUE if p is a lookaside memory allocation from db
 269 */
 270 #ifndef SQLITE_OMIT_LOOKASIDE
 271 static int isLookaside(sqlite3 *db, void *p){
 272   return SQLITE_WITHIN(p, db->lookaside.pStart, db->lookaside.pEnd);
 273 }
 274 #else
 275 #define isLookaside(A,B) 0
 276 #endif
 277
 278 /*
 279 ** Return the size of a memory allocation previously obtained from
 280 ** sqlite3Malloc() or sqlite3_malloc().
 281 */
 282 int sqlite3MallocSize(void *p){
 283   assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
 284   return sqlite3GlobalConfig.m.xSize(p);
 285 }
 286 int sqlite3DbMallocSize(sqlite3 *db, void *p){
 287   assert( p!=0 );
 288   if( db==0 || !isLookaside(db,p) ){
 289 #ifdef SQLITE_DEBUG
 290     if( db==0 ){
 291       assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_HEAP) );
 292       assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
 293     }else{
 294       assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
 295       assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
 296     }
 297 #endif
 298     return sqlite3GlobalConfig.m.xSize(p);
 299   }else{
 300     assert( sqlite3_mutex_held(db->mutex) );
 301     return db->lookaside.sz;
 302   }
 303 }
 304 sqlite3_uint64 sqlite3_msize(void *p){
 305   assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_HEAP) );
 306   assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
 307   return p ? sqlite3GlobalConfig.m.xSize(p) : 0;
 308 }
 309
 310 /*
 311 ** Free memory previously obtained from sqlite3Malloc().
 312 */
 313 void sqlite3_free(void *p){
 314   if( p==0 ) return;  /* IMP: R-49053-54554 */
 315   assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
 316   assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_HEAP) );
 317   if( sqlite3GlobalConfig.bMemstat ){
 318     sqlite3_mutex_enter(mem0.mutex);
 319     sqlite3StatusDown(SQLITE_STATUS_MEMORY_USED, sqlite3MallocSize(p));
 320     sqlite3StatusDown(SQLITE_STATUS_MALLOC_COUNT, 1);
 321     sqlite3GlobalConfig.m.xFree(p);
 322     sqlite3_mutex_leave(mem0.mutex);
 323   }else{
 324     sqlite3GlobalConfig.m.xFree(p);
 325   }
 326 }
 327
 328 /*
 329 ** Add the size of memory allocation "p" to the count in
 330 ** *db->pnBytesFreed.
 331 */
 332 static SQLITE_NOINLINE void measureAllocationSize(sqlite3 *db, void *p){
 333   *db->pnBytesFreed += sqlite3DbMallocSize(db,p);
 334 }
 335
 336 /*
 337 ** Free memory that might be associated with a particular database
 338 ** connection.  Calling sqlite3DbFree(D,X) for X==0 is a harmless no-op.
 339 ** The sqlite3DbFreeNN(D,X) version requires that X be non-NULL.
 340 */
 341 void sqlite3DbFreeNN(sqlite3 *db, void *p){
 342   assert( db==0 || sqlite3_mutex_held(db->mutex) );
 343   assert( p!=0 );
 344   if( db ){
 345     if( db->pnBytesFreed ){
 346       measureAllocationSize(db, p);
 347       return;
 348     }
 349     if( isLookaside(db, p) ){
 350       LookasideSlot *pBuf = (LookasideSlot*)p;
 351 #ifdef SQLITE_DEBUG
 352       /* Trash all content in the buffer being freed */
 353       memset(p, 0xaa, db->lookaside.sz);
 354 #endif
 355       pBuf->pNext = db->lookaside.pFree;
 356       db->lookaside.pFree = pBuf;
 357       return;
 358     }
 359   }
 360   assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
 361   assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
 362   assert( db!=0 || sqlite3MemdebugNoType(p, MEMTYPE_LOOKASIDE) );
 363   sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
 364   sqlite3_free(p);
 365 }
 366 void sqlite3DbFree(sqlite3 *db, void *p){
 367   assert( db==0 || sqlite3_mutex_held(db->mutex) );
 368   if( p ) sqlite3DbFreeNN(db, p);
 369 }
 370
 371 /*
 372 ** Change the size of an existing memory allocation
 373 */
 374 void *sqlite3Realloc(void *pOld, u64 nBytes){
 375   int nOld, nNew, nDiff;
 376   void *pNew;
 377   assert( sqlite3MemdebugHasType(pOld, MEMTYPE_HEAP) );
 378   assert( sqlite3MemdebugNoType(pOld, (u8)~MEMTYPE_HEAP) );
 379   if( pOld==0 ){
 380     return sqlite3Malloc(nBytes); /* IMP: R-04300-56712 */
 381   }
 382   if( nBytes==0 ){
 383     sqlite3_free(pOld); /* IMP: R-26507-47431 */
 384     return 0;
 385   }
 386   if( nBytes>=0x7fffff00 ){
 387     /* The 0x7ffff00 limit term is explained in comments on sqlite3Malloc() */
 388     return 0;
 389   }
 390   nOld = sqlite3MallocSize(pOld);
 391   /* IMPLEMENTATION-OF: R-46199-30249 SQLite guarantees that the second
 392   ** argument to xRealloc is always a value returned by a prior call to
 393   ** xRoundup. */
 394   nNew = sqlite3GlobalConfig.m.xRoundup((int)nBytes);
 395   if( nOld==nNew ){
 396     pNew = pOld;
 397   }else if( sqlite3GlobalConfig.bMemstat ){
 398     sqlite3_mutex_enter(mem0.mutex);
 399     sqlite3StatusHighwater(SQLITE_STATUS_MALLOC_SIZE, (int)nBytes);
 400     nDiff = nNew - nOld;
 401     if( nDiff>0 && sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED) >=
 402           mem0.alarmThreshold-nDiff ){
 403       sqlite3MallocAlarm(nDiff);
 404     }
 405     pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
 406     if( pNew==0 && mem0.alarmThreshold>0 ){
 407       sqlite3MallocAlarm((int)nBytes);
 408       pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
 409     }
 410     if( pNew ){
 411       nNew = sqlite3MallocSize(pNew);
 412       sqlite3StatusUp(SQLITE_STATUS_MEMORY_USED, nNew-nOld);
 413     }
 414     sqlite3_mutex_leave(mem0.mutex);
 415   }else{
 416     pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
 417   }
 418   assert( EIGHT_BYTE_ALIGNMENT(pNew) ); /* IMP: R-11148-40995 */
 419   return pNew;
 420 }
 421
 422 /*
 423 ** The public interface to sqlite3Realloc.  Make sure that the memory
 424 ** subsystem is initialized prior to invoking sqliteRealloc.
 425 */
 426 void *sqlite3_realloc(void *pOld, int n){
 427 #ifndef SQLITE_OMIT_AUTOINIT
 428   if( sqlite3_initialize() ) return 0;
 429 #endif
 430   if( n<0 ) n = 0;  /* IMP: R-26507-47431 */
 431   return sqlite3Realloc(pOld, n);
 432 }
 433 void *sqlite3_realloc64(void *pOld, sqlite3_uint64 n){
 434 #ifndef SQLITE_OMIT_AUTOINIT
 435   if( sqlite3_initialize() ) return 0;
 436 #endif
 437   return sqlite3Realloc(pOld, n);
 438 }
 439
 440
 441 /*
 442 ** Allocate and zero memory.
 443 */
 444 void *sqlite3MallocZero(u64 n){
 445   void *p = sqlite3Malloc(n);
 446   if( p ){
 447     memset(p, 0, (size_t)n);
 448   }
 449   return p;
 450 }
 451
 452 /*
 453 ** Allocate and zero memory.  If the allocation fails, make
 454 ** the mallocFailed flag in the connection pointer.
 455 */
 456 void *sqlite3DbMallocZero(sqlite3 *db, u64 n){
 457   void *p;
 458   testcase( db==0 );
 459   p = sqlite3DbMallocRaw(db, n);
 460   if( p ) memset(p, 0, (size_t)n);
 461   return p;
 462 }
 463
 464
 465 /* Finish the work of sqlite3DbMallocRawNN for the unusual and
 466 ** slower case when the allocation cannot be fulfilled using lookaside.
 467 */
 468 static SQLITE_NOINLINE void *dbMallocRawFinish(sqlite3 *db, u64 n){
 469   void *p;
 470   assert( db!=0 );
 471   p = sqlite3Malloc(n);
 472   if( !p ) sqlite3OomFault(db);
 473   sqlite3MemdebugSetType(p,
 474          (db->lookaside.bDisable==0) ? MEMTYPE_LOOKASIDE : MEMTYPE_HEAP);
 475   return p;
 476 }
 477
 478 /*
 479 ** Allocate memory, either lookaside (if possible) or heap.
 480 ** If the allocation fails, set the mallocFailed flag in
 481 ** the connection pointer.
 482 **
 483 ** If db!=0 and db->mallocFailed is true (indicating a prior malloc
 484 ** failure on the same database connection) then always return 0.
 485 ** Hence for a particular database connection, once malloc starts
 486 ** failing, it fails consistently until mallocFailed is reset.
 487 ** This is an important assumption.  There are many places in the
 488 ** code that do things like this:
 489 **
 490 **         int *a = (int*)sqlite3DbMallocRaw(db, 100);
 491 **         int *b = (int*)sqlite3DbMallocRaw(db, 200);
 492 **         if( b ) a[10] = 9;
 493 **
 494 ** In other words, if a subsequent malloc (ex: "b") worked, it is assumed
 495 ** that all prior mallocs (ex: "a") worked too.
 496 **
 497 ** The sqlite3MallocRawNN() variant guarantees that the "db" parameter is
 498 ** not a NULL pointer.
 499 */
 500 void *sqlite3DbMallocRaw(sqlite3 *db, u64 n){
 501   void *p;
 502   if( db ) return sqlite3DbMallocRawNN(db, n);
 503   p = sqlite3Malloc(n);
 504   sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
 505   return p;
 506 }
 507 void *sqlite3DbMallocRawNN(sqlite3 *db, u64 n){
 508 #ifndef SQLITE_OMIT_LOOKASIDE
 509   LookasideSlot *pBuf;
 510   assert( db!=0 );
 511   assert( sqlite3_mutex_held(db->mutex) );
 512   assert( db->pnBytesFreed==0 );
 513   if( db->lookaside.bDisable==0 ){
 514     assert( db->mallocFailed==0 );
 515     if( n>db->lookaside.sz ){
 516       db->lookaside.anStat[1]++;
 517     }else if( (pBuf = db->lookaside.pFree)!=0 ){
 518       db->lookaside.pFree = pBuf->pNext;
 519       db->lookaside.anStat[0]++;
 520       return (void*)pBuf;
 521     }else if( (pBuf = db->lookaside.pInit)!=0 ){
 522       db->lookaside.pInit = pBuf->pNext;
 523       db->lookaside.anStat[0]++;
 524       return (void*)pBuf;
 525     }else{
 526       db->lookaside.anStat[2]++;
 527     }
 528   }else if( db->mallocFailed ){
 529     return 0;
 530   }
 531 #else
 532   assert( db!=0 );
 533   assert( sqlite3_mutex_held(db->mutex) );
 534   assert( db->pnBytesFreed==0 );
 535   if( db->mallocFailed ){
 536     return 0;
 537   }
 538 #endif
 539   return dbMallocRawFinish(db, n);
 540 }
 541
 542 /* Forward declaration */
 543 static SQLITE_NOINLINE void *dbReallocFinish(sqlite3 *db, void *p, u64 n);
 544
 545 /*
 546 ** Resize the block of memory pointed to by p to n bytes. If the
 547 ** resize fails, set the mallocFailed flag in the connection object.
 548 */
 549 void *sqlite3DbRealloc(sqlite3 *db, void *p, u64 n){
 550   assert( db!=0 );
 551   if( p==0 ) return sqlite3DbMallocRawNN(db, n);
 552   assert( sqlite3_mutex_held(db->mutex) );
 553   if( isLookaside(db,p) && n<=db->lookaside.sz ) return p;
 554   return dbReallocFinish(db, p, n);
 555 }
 556 static SQLITE_NOINLINE void *dbReallocFinish(sqlite3 *db, void *p, u64 n){
 557   void *pNew = 0;
 558   assert( db!=0 );
 559   assert( p!=0 );
 560   if( db->mallocFailed==0 ){
 561     if( isLookaside(db, p) ){
 562       pNew = sqlite3DbMallocRawNN(db, n);
 563       if( pNew ){
 564         memcpy(pNew, p, db->lookaside.sz);
 565         sqlite3DbFree(db, p);
 566       }
 567     }else{
 568       assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
 569       assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
 570       sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
 571       pNew = sqlite3_realloc64(p, n);
 572       if( !pNew ){
 573         sqlite3OomFault(db);
 574       }
 575       sqlite3MemdebugSetType(pNew,
 576             (db->lookaside.bDisable==0 ? MEMTYPE_LOOKASIDE : MEMTYPE_HEAP));
 577     }
 578   }
 579   return pNew;
 580 }
 581
 582 /*
 583 ** Attempt to reallocate p.  If the reallocation fails, then free p
 584 ** and set the mallocFailed flag in the database connection.
 585 */
 586 void *sqlite3DbReallocOrFree(sqlite3 *db, void *p, u64 n){
 587   void *pNew;
 588   pNew = sqlite3DbRealloc(db, p, n);
 589   if( !pNew ){
 590     sqlite3DbFree(db, p);
 591   }
 592   return pNew;
 593 }
 594
 595 /*
 596 ** Make a copy of a string in memory obtained from sqliteMalloc(). These
 597 ** functions call sqlite3MallocRaw() directly instead of sqliteMalloc(). This
 598 ** is because when memory debugging is turned on, these two functions are
 599 ** called via macros that record the current file and line number in the
 600 ** ThreadData structure.
 601 */
 602 char *sqlite3DbStrDup(sqlite3 *db, const char *z){
 603   char *zNew;
 604   size_t n;
 605   if( z==0 ){
 606     return 0;
 607   }
 608   n = strlen(z) + 1;
 609   zNew = sqlite3DbMallocRaw(db, n);
 610   if( zNew ){
 611     memcpy(zNew, z, n);
 612   }
 613   return zNew;
 614 }
 615 char *sqlite3DbStrNDup(sqlite3 *db, const char *z, u64 n){
 616   char *zNew;
 617   assert( db!=0 );
 618   if( z==0 ){
 619     return 0;
 620   }
 621   assert( (n&0x7fffffff)==n );
 622   zNew = sqlite3DbMallocRawNN(db, n+1);
 623   if( zNew ){
 624     memcpy(zNew, z, (size_t)n);
 625     zNew[n] = 0;
 626   }
 627   return zNew;
 628 }
 629
 630 /*
 631 ** The text between zStart and zEnd represents a phrase within a larger
 632 ** SQL statement.  Make a copy of this phrase in space obtained form
 633 ** sqlite3DbMalloc().  Omit leading and trailing whitespace.
 634 */
 635 char *sqlite3DbSpanDup(sqlite3 *db, const char *zStart, const char *zEnd){
 636   int n;
 637   while( sqlite3Isspace(zStart[0]) ) zStart++;
 638   n = (int)(zEnd - zStart);
 639   while( ALWAYS(n>0) && sqlite3Isspace(zStart[n-1]) ) n--;
 640   return sqlite3DbStrNDup(db, zStart, n);
 641 }
 642
 643 /*
 644 ** Free any prior content in *pz and replace it with a copy of zNew.
 645 */
 646 void sqlite3SetString(char **pz, sqlite3 *db, const char *zNew){
 647   sqlite3DbFree(db, *pz);
 648   *pz = sqlite3DbStrDup(db, zNew);
 649 }
 650
 651 /*
 652 ** Call this routine to record the fact that an OOM (out-of-memory) error
 653 ** has happened.  This routine will set db->mallocFailed, and also
 654 ** temporarily disable the lookaside memory allocator and interrupt
 655 ** any running VDBEs.
 656 */
 657 void sqlite3OomFault(sqlite3 *db){
 658   if( db->mallocFailed==0 && db->bBenignMalloc==0 ){
 659     db->mallocFailed = 1;
 660     if( db->nVdbeExec>0 ){
 661       db->u1.isInterrupted = 1;
 662     }
 663     db->lookaside.bDisable++;
 664   }
 665 }
 666
 667 /*
 668 ** This routine reactivates the memory allocator and clears the
 669 ** db->mallocFailed flag as necessary.
 670 **
 671 ** The memory allocator is not restarted if there are running
 672 ** VDBEs.
 673 */
 674 void sqlite3OomClear(sqlite3 *db){
 675   if( db->mallocFailed && db->nVdbeExec==0 ){
 676     db->mallocFailed = 0;
 677     db->u1.isInterrupted = 0;
 678     assert( db->lookaside.bDisable>0 );
 679     db->lookaside.bDisable--;
 680   }
 681 }
 682
 683 /*
 684 ** Take actions at the end of an API call to indicate an OOM error
 685 */
 686 static SQLITE_NOINLINE int apiOomError(sqlite3 *db){
 687   sqlite3OomClear(db);
 688   sqlite3Error(db, SQLITE_NOMEM);
 689   return SQLITE_NOMEM_BKPT;
 690 }
 691
 692 /*
 693 ** This function must be called before exiting any API function (i.e.
 694 ** returning control to the user) that has called sqlite3_malloc or
 695 ** sqlite3_realloc.
 696 **
 697 ** The returned value is normally a copy of the second argument to this
 698 ** function. However, if a malloc() failure has occurred since the previous
 699 ** invocation SQLITE_NOMEM is returned instead.
 700 **
 701 ** If an OOM as occurred, then the connection error-code (the value
 702 ** returned by sqlite3_errcode()) is set to SQLITE_NOMEM.
 703 */
 704 int sqlite3ApiExit(sqlite3* db, int rc){
 705   /* If the db handle must hold the connection handle mutex here.
 706   ** Otherwise the read (and possible write) of db->mallocFailed
 707   ** is unsafe, as is the call to sqlite3Error().
 708   */
 709   assert( db!=0 );
 710   assert( sqlite3_mutex_held(db->mutex) );
 711   if( db->mallocFailed || rc==SQLITE_IOERR_NOMEM ){
 712     return apiOomError(db);
 713   }
 714   return rc & db->errMask;
 715 }