src/fault.c

   1 /*
   2 ** 2008 Jan 22
   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 ** This file contains code to support the concept of "benign"
  14 ** malloc failures (when the xMalloc() or xRealloc() method of the
  15 ** sqlite3_mem_methods structure fails to allocate a block of memory
  16 ** and returns 0).
  17 **
  18 ** Most malloc failures are non-benign. After they occur, SQLite
  19 ** abandons the current operation and returns an error code (usually
  20 ** SQLITE_NOMEM) to the user. However, sometimes a fault is not necessarily
  21 ** fatal. For example, if a malloc fails while resizing a hash table, this
  22 ** is completely recoverable simply by not carrying out the resize. The
  23 ** hash table will continue to function normally.  So a malloc failure
  24 ** during a hash table resize is a benign fault.
  25 */
  26
  27 #include "sqliteInt.h"
  28
  29 #ifndef SQLITE_UNTESTABLE
  30
  31 /*
  32 ** Global variables.
  33 */
  34 typedef struct BenignMallocHooks BenignMallocHooks;
  35 static SQLITE_WSD struct BenignMallocHooks {
  36   void (*xBenignBegin)(void);
  37   void (*xBenignEnd)(void);
  38 } sqlite3Hooks = { 0, 0 };
  39
  40 /* The "wsdHooks" macro will resolve to the appropriate BenignMallocHooks
  41 ** structure.  If writable static data is unsupported on the target,
  42 ** we have to locate the state vector at run-time.  In the more common
  43 ** case where writable static data is supported, wsdHooks can refer directly
  44 ** to the "sqlite3Hooks" state vector declared above.
  45 */
  46 #ifdef SQLITE_OMIT_WSD
  47 # define wsdHooksInit \
  48   BenignMallocHooks *x = &GLOBAL(BenignMallocHooks,sqlite3Hooks)
  49 # define wsdHooks x[0]
  50 #else
  51 # define wsdHooksInit
  52 # define wsdHooks sqlite3Hooks
  53 #endif
  54
  55
  56 /*
  57 ** Register hooks to call when sqlite3BeginBenignMalloc() and
  58 ** sqlite3EndBenignMalloc() are called, respectively.
  59 */
  60 void sqlite3BenignMallocHooks(
  61   void (*xBenignBegin)(void),
  62   void (*xBenignEnd)(void)
  63 ){
  64   wsdHooksInit;
  65   wsdHooks.xBenignBegin = xBenignBegin;
  66   wsdHooks.xBenignEnd = xBenignEnd;
  67 }
  68
  69 /*
  70 ** This (sqlite3EndBenignMalloc()) is called by SQLite code to indicate that
  71 ** subsequent malloc failures are benign. A call to sqlite3EndBenignMalloc()
  72 ** indicates that subsequent malloc failures are non-benign.
  73 */
  74 void sqlite3BeginBenignMalloc(void){
  75   wsdHooksInit;
  76   if( wsdHooks.xBenignBegin ){
  77     wsdHooks.xBenignBegin();
  78   }
  79 }
  80 void sqlite3EndBenignMalloc(void){
  81   wsdHooksInit;
  82   if( wsdHooks.xBenignEnd ){
  83     wsdHooks.xBenignEnd();
  84   }
  85 }
  86
  87 #endif   /* #ifndef SQLITE_UNTESTABLE */