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      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_OMIT_BUILTIN_TEST
     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_OMIT_BUILTIN_TEST */
     88