persistentstorage/sqlite3api/SQLite/fault.c
author Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
Fri, 22 Jan 2010 11:06:30 +0200
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/*
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** 2008 Jan 22
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**
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** The author disclaims copyright to this source code.  In place of
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** a legal notice, here is a blessing:
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**
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**    May you do good and not evil.
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**    May you find forgiveness for yourself and forgive others.
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**    May you share freely, never taking more than you give.
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**
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*************************************************************************
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**
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** $Id: fault.c,v 1.11 2008/09/02 00:52:52 drh Exp $
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*/
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/*
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** This file contains code to support the concept of "benign" 
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** malloc failures (when the xMalloc() or xRealloc() method of the
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** sqlite3_mem_methods structure fails to allocate a block of memory
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** and returns 0). 
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**
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** Most malloc failures are non-benign. After they occur, SQLite
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** abandons the current operation and returns an error code (usually
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** SQLITE_NOMEM) to the user. However, sometimes a fault is not necessarily
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** fatal. For example, if a malloc fails while resizing a hash table, this 
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** is completely recoverable simply by not carrying out the resize. The 
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** hash table will continue to function normally.  So a malloc failure 
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** during a hash table resize is a benign fault.
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*/
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#include "sqliteInt.h"
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#ifndef SQLITE_OMIT_BUILTIN_TEST
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/*
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** Global variables.
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*/
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typedef struct BenignMallocHooks BenignMallocHooks;
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static SQLITE_WSD struct BenignMallocHooks {
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  void (*xBenignBegin)(void);
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  void (*xBenignEnd)(void);
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} sqlite3Hooks = { 0, 0 };
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/* The "wsdHooks" macro will resolve to the appropriate BenignMallocHooks
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** structure.  If writable static data is unsupported on the target,
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** we have to locate the state vector at run-time.  In the more common
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** case where writable static data is supported, wsdHooks can refer directly
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** to the "sqlite3Hooks" state vector declared above.
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*/
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#ifdef SQLITE_OMIT_WSD
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# define wsdHooksInit \
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  BenignMallocHooks *x = &GLOBAL(BenignMallocHooks,sqlite3Hooks)
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# define wsdHooks x[0]
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#else
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# define wsdHooksInit
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# define wsdHooks sqlite3Hooks
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#endif
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/*
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** Register hooks to call when sqlite3BeginBenignMalloc() and
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** sqlite3EndBenignMalloc() are called, respectively.
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*/
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void sqlite3BenignMallocHooks(
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  void (*xBenignBegin)(void),
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  void (*xBenignEnd)(void)
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){
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  wsdHooksInit;
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  wsdHooks.xBenignBegin = xBenignBegin;
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  wsdHooks.xBenignEnd = xBenignEnd;
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}
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/*
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** This (sqlite3EndBenignMalloc()) is called by SQLite code to indicate that
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** subsequent malloc failures are benign. A call to sqlite3EndBenignMalloc()
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** indicates that subsequent malloc failures are non-benign.
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*/
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void sqlite3BeginBenignMalloc(void){
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  wsdHooksInit;
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  if( wsdHooks.xBenignBegin ){
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    wsdHooks.xBenignBegin();
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  }
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}
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void sqlite3EndBenignMalloc(void){
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  wsdHooksInit;
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  if( wsdHooks.xBenignEnd ){
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    wsdHooks.xBenignEnd();
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  }
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}
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#endif   /* #ifndef SQLITE_OMIT_BUILTIN_TEST */