/*
** 2007 August 15
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the C functions that implement a memory
** allocation subsystem for use by SQLite.
**
** $Id: mem2.c,v 1.8 2007/08/23 02:47:53 drh Exp $
*/
/*
** This version of the memory allocator is used only if the
** SQLITE_MEMDEBUG macro is defined and SQLITE_OMIT_MEMORY_ALLOCATION
** is not defined.
*/
#if defined(SQLITE_MEMDEBUG) && !defined(SQLITE_OMIT_MEMORY_ALLOCATION)
/*
** We will eventually construct multiple memory allocation subsystems
** suitable for use in various contexts:
**
** * Normal multi-threaded builds
** * Normal single-threaded builds
** * Debugging builds
**
** This version is suitable for use in debugging builds.
**
** Features:
**
** * Every allocate has guards at both ends.
** * New allocations are initialized with randomness
** * Allocations are overwritten with randomness when freed
** * Optional logs of malloc activity generated
** * Summary of outstanding allocations with backtraces to the
** point of allocation.
** * The ability to simulate memory allocation failure
*/
#include "sqliteInt.h"
#include <stdio.h>
/*
** The backtrace functionality is only available with GLIBC
*/
#ifdef __GLIBC__
extern int backtrace(void**,int);
extern void backtrace_symbols_fd(void*const*,int,int);
#else
# define backtrace(A,B) 0
# define backtrace_symbols_fd(A,B,C)
#endif
/*
** Each memory allocation looks like this:
**
** ------------------------------------------------------------------------
** | Title | backtrace pointers | MemBlockHdr | allocation | EndGuard |
** ------------------------------------------------------------------------
**
** The application code sees only a pointer to the allocation. We have
** to back up from the allocation pointer to find the MemBlockHdr. The
** MemBlockHdr tells us the size of the allocation and the number of
** backtrace pointers. There is also a guard word at the end of the
** MemBlockHdr.
*/
struct MemBlockHdr {
struct MemBlockHdr *pNext, *pPrev; /* Linked list of all unfreed memory */
unsigned int iSize; /* Size of this allocation */
unsigned char nBacktrace; /* Number of backtraces on this alloc */
unsigned char nBacktraceSlots; /* Available backtrace slots */
unsigned short nTitle; /* Bytes of title; includes '\0' */
unsigned int iForeGuard; /* Guard word for sanity */
};
/*
** Guard words
*/
#define FOREGUARD 0x80F5E153
#define REARGUARD 0xE4676B53
/*
** All of the static variables used by this module are collected
** into a single structure named "mem". This is to keep the
** static variables organized and to reduce namespace pollution
** when this module is combined with other in the amalgamation.
*/
static struct {
/*
** The alarm callback and its arguments. The mem.mutex lock will
** be held while the callback is running. Recursive calls into
** the memory subsystem are allowed, but no new callbacks will be
** issued. The alarmBusy variable is set to prevent recursive
** callbacks.
*/
sqlite3_uint64 alarmThreshold;
void (*alarmCallback)(void*, sqlite3_uint64, unsigned);
void *alarmArg;
int alarmBusy;
/*
** Mutex to control access to the memory allocation subsystem.
*/
sqlite3_mutex *mutex;
/*
** Current allocation and high-water mark.
*/
sqlite3_uint64 nowUsed;
sqlite3_uint64 mxUsed;
/*
** Head and tail of a linked list of all outstanding allocations
*/
struct MemBlockHdr *pFirst;
struct MemBlockHdr *pLast;
/*
** The number of levels of backtrace to save in new allocations.
*/
int nBacktrace;
/*
** Title text to insert in front of each block
*/
int nTitle; /* Bytes of zTitle to save. Includes '\0' and padding */
char zTitle[100]; /* The title text */
/*
** These values are used to simulate malloc failures. When
** iFail is 1, simulate a malloc failures and reset the value
** to iReset.
*/
int iFail; /* Decrement and fail malloc when this is 1 */
int iReset; /* When malloc fails set iiFail to this value */
int iFailCnt; /* Number of failures */
/*
** sqlite3MallocDisallow() increments the following counter.
** sqlite3MallocAllow() decrements it.
*/
int disallow; /* Do not allow memory allocation */
} mem = { /* This variable holds all of the local data */
((sqlite3_uint64)1)<<63, /* alarmThreshold */
/* Everything else is initialized to zero */
};
/*
** Return the amount of memory currently checked out.
*/
sqlite3_uint64 sqlite3_memory_used(void){
sqlite3_uint64 n;
if( mem.mutex==0 ){
mem.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM);
}
sqlite3_mutex_enter(mem.mutex);
n = mem.nowUsed;
sqlite3_mutex_leave(mem.mutex);
return n;
}
/*
** Return the maximum amount of memory that has ever been
** checked out since either the beginning of this process
** or since the most recent reset.
*/
sqlite3_uint64 sqlite3_memory_highwater(int resetFlag){
sqlite3_uint64 n;
if( mem.mutex==0 ){
mem.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM);
}
sqlite3_mutex_enter(mem.mutex);
n = mem.mxUsed;
if( resetFlag ){
mem.mxUsed = mem.nowUsed;
}
sqlite3_mutex_leave(mem.mutex);
return n;
}
/*
** Change the alarm callback
*/
int sqlite3_memory_alarm(
void(*xCallback)(void *pArg, sqlite3_uint64 used, unsigned int N),
void *pArg,
sqlite3_uint64 iThreshold
){
if( mem.mutex==0 ){
mem.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM);
}
sqlite3_mutex_enter(mem.mutex);
mem.alarmCallback = xCallback;
mem.alarmArg = pArg;
mem.alarmThreshold = iThreshold;
sqlite3_mutex_leave(mem.mutex);
return SQLITE_OK;
}
/*
** Trigger the alarm
*/
static void sqlite3MemsysAlarm(unsigned nByte){
void (*xCallback)(void*,sqlite3_uint64,unsigned);
sqlite3_uint64 nowUsed;
void *pArg;
if( mem.alarmCallback==0 || mem.alarmBusy ) return;
mem.alarmBusy = 1;
xCallback = mem.alarmCallback;
nowUsed = mem.nowUsed;
pArg = mem.alarmArg;
sqlite3_mutex_leave(mem.mutex);
xCallback(pArg, nowUsed, nByte);
sqlite3_mutex_enter(mem.mutex);
mem.alarmBusy = 0;
}
/*
** Given an allocation, find the MemBlockHdr for that allocation.
**
** This routine checks the guards at either end of the allocation and
** if they are incorrect it asserts.
*/
static struct MemBlockHdr *sqlite3MemsysGetHeader(void *pAllocation){
struct MemBlockHdr *p;
unsigned int *pInt;
p = (struct MemBlockHdr*)pAllocation;
p--;
assert( p->iForeGuard==FOREGUARD );
assert( (p->iSize & 3)==0 );
pInt = (unsigned int*)pAllocation;
assert( pInt[p->iSize/sizeof(unsigned int)]==REARGUARD );
return p;
}
/*
** This routine is called once the first time a simulated memory
** failure occurs. The sole purpose of this routine is to provide
** a convenient place to set a debugger breakpoint when debugging
** errors related to malloc() failures.
*/
static void sqlite3MemsysFailed(void){
mem.iFailCnt = 0;
}
/*
** Allocate nByte bytes of memory.
*/
void *sqlite3_malloc(int nByte){
struct MemBlockHdr *pHdr;
void **pBt;
char *z;
unsigned int *pInt;
void *p;
unsigned int totalSize;
if( nByte<=0 ){
return 0;
}
if( mem.mutex==0 ){
mem.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM);
}
sqlite3_mutex_enter(mem.mutex);
assert( mem.disallow==0 );
if( mem.nowUsed+nByte>=mem.alarmThreshold ){
sqlite3MemsysAlarm(nByte);
}
nByte = (nByte+3)&~3;
totalSize = nByte + sizeof(*pHdr) + sizeof(unsigned int) +
mem.nBacktrace*sizeof(void*) + mem.nTitle;
if( mem.iFail>0 ){
if( mem.iFail==1 ){
p = 0;
mem.iFail = mem.iReset;
if( mem.iFailCnt==0 ){
sqlite3MemsysFailed(); /* A place to set a breakpoint */
}
mem.iFailCnt++;
}else{
p = malloc(totalSize);
mem.iFail--;
}
}else{
p = malloc(totalSize);
if( p==0 ){
sqlite3MemsysAlarm(nByte);
p = malloc(totalSize);
}
}
if( p ){
z = p;
pBt = (void**)&z[mem.nTitle];
pHdr = (struct MemBlockHdr*)&pBt[mem.nBacktrace];
pHdr->pNext = 0;
pHdr->pPrev = mem.pLast;
if( mem.pLast ){
mem.pLast->pNext = pHdr;
}else{
mem.pFirst = pHdr;
}
mem.pLast = pHdr;
pHdr->iForeGuard = FOREGUARD;
pHdr->nBacktraceSlots = mem.nBacktrace;
pHdr->nTitle = mem.nTitle;
if( mem.nBacktrace ){
void *aAddr[40];
pHdr->nBacktrace = backtrace(aAddr, mem.nBacktrace+1)-1;
memcpy(pBt, &aAddr[1], pHdr->nBacktrace*sizeof(void*));
}else{
pHdr->nBacktrace = 0;
}
if( mem.nTitle ){
memcpy(z, mem.zTitle, mem.nTitle);
}
pHdr->iSize = nByte;
pInt = (unsigned int *)&pHdr[1];
pInt[nByte/sizeof(unsigned int)] = REARGUARD;
memset(pInt, 0x65, nByte);
mem.nowUsed += nByte;
if( mem.nowUsed>mem.mxUsed ){
mem.mxUsed = mem.nowUsed;
}
p = (void*)pInt;
}
sqlite3_mutex_leave(mem.mutex);
return p;
}
/*
** Free memory.
*/
void sqlite3_free(void *pPrior){
struct MemBlockHdr *pHdr;
void **pBt;
char *z;
if( pPrior==0 ){
return;
}
assert( mem.mutex!=0 );
pHdr = sqlite3MemsysGetHeader(pPrior);
pBt = (void**)pHdr;
pBt -= pHdr->nBacktraceSlots;
sqlite3_mutex_enter(mem.mutex);
mem.nowUsed -= pHdr->iSize;
if( pHdr->pPrev ){
assert( pHdr->pPrev->pNext==pHdr );
pHdr->pPrev->pNext = pHdr->pNext;
}else{
assert( mem.pFirst==pHdr );
mem.pFirst = pHdr->pNext;
}
if( pHdr->pNext ){
assert( pHdr->pNext->pPrev==pHdr );
pHdr->pNext->pPrev = pHdr->pPrev;
}else{
assert( mem.pLast==pHdr );
mem.pLast = pHdr->pPrev;
}
z = (char*)pBt;
z -= pHdr->nTitle;
memset(z, 0x2b, sizeof(void*)*pHdr->nBacktraceSlots + sizeof(*pHdr) +
pHdr->iSize + sizeof(unsigned int) + pHdr->nTitle);
free(z);
sqlite3_mutex_leave(mem.mutex);
}
/*
** Change the size of an existing memory allocation.
**
** For this debugging implementation, we *always* make a copy of the
** allocation into a new place in memory. In this way, if the
** higher level code is using pointer to the old allocation, it is
** much more likely to break and we are much more liking to find
** the error.
*/
void *sqlite3_realloc(void *pPrior, int nByte){
struct MemBlockHdr *pOldHdr;
void *pNew;
if( pPrior==0 ){
return sqlite3_malloc(nByte);
}
if( nByte<=0 ){
sqlite3_free(pPrior);
return 0;
}
assert( mem.disallow==0 );
pOldHdr = sqlite3MemsysGetHeader(pPrior);
pNew = sqlite3_malloc(nByte);
if( pNew ){
memcpy(pNew, pPrior, nByte<pOldHdr->iSize ? nByte : pOldHdr->iSize);
if( nByte>pOldHdr->iSize ){
memset(&((char*)pNew)[pOldHdr->iSize], 0x2b, nByte - pOldHdr->iSize);
}
sqlite3_free(pPrior);
}
return pNew;
}
/*
** Set the number of backtrace levels kept for each allocation.
** A value of zero turns of backtracing. The number is always rounded
** up to a multiple of 2.
*/
void sqlite3_memdebug_backtrace(int depth){
if( depth<0 ){ depth = 0; }
if( depth>20 ){ depth = 20; }
depth = (depth+1)&0xfe;
mem.nBacktrace = depth;
}
/*
** Set the title string for subsequent allocations.
*/
void sqlite3_memdebug_settitle(const char *zTitle){
int n = strlen(zTitle) + 1;
if( mem.mutex==0 ){
mem.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM);
}
sqlite3_mutex_enter(mem.mutex);
if( n>=sizeof(mem.zTitle) ) n = sizeof(mem.zTitle)-1;
memcpy(mem.zTitle, zTitle, n);
mem.zTitle[n] = 0;
mem.nTitle = (n+3)&~3;
sqlite3_mutex_leave(mem.mutex);
}
/*
** Open the file indicated and write a log of all unfreed memory
** allocations into that log.
*/
void sqlite3_memdebug_dump(const char *zFilename){
FILE *out;
struct MemBlockHdr *pHdr;
void **pBt;
out = fopen(zFilename, "w");
if( out==0 ){
fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
zFilename);
return;
}
for(pHdr=mem.pFirst; pHdr; pHdr=pHdr->pNext){
char *z = (char*)pHdr;
z -= pHdr->nBacktraceSlots*sizeof(void*) + pHdr->nTitle;
fprintf(out, "**** %d bytes at %p from %s ****\n", pHdr->iSize,&pHdr[1],z);
if( pHdr->nBacktrace ){
fflush(out);
pBt = (void**)pHdr;
pBt -= pHdr->nBacktraceSlots;
backtrace_symbols_fd(pBt, pHdr->nBacktrace, fileno(out));
fprintf(out, "\n");
}
}
fclose(out);
}
/*
** This routine is used to simulate malloc failures.
**
** After calling this routine, there will be iFail successful
** memory allocations and then a failure. If iRepeat is 1
** all subsequent memory allocations will fail. If iRepeat is
** 0, only a single allocation will fail. If iRepeat is negative
** then the previous setting for iRepeat is unchanged.
**
** Each call to this routine overrides the previous. To disable
** the simulated allocation failure mechanism, set iFail to -1.
**
** This routine returns the number of simulated failures that have
** occurred since the previous call.
*/
int sqlite3_memdebug_fail(int iFail, int iRepeat){
int n = mem.iFailCnt;
mem.iFail = iFail+1;
if( iRepeat>=0 ){
mem.iReset = iRepeat;
}
mem.iFailCnt = 0;
return n;
}
/*
** This routine returns the number of successful mallocs remaining until
** the next simulated malloc failure. -1 is returned if no simulated
** failure is currently scheduled.
*/
int sqlite3_memdebug_pending(void){
return mem.iFail-1;
}
/*
** The following two routines are used to assert that no memory
** allocations occur between one call and the next. The use of
** these routines does not change the computed results in any way.
** These routines are like asserts.
*/
void sqlite3MallocDisallow(void){
assert( mem.mutex!=0 );
sqlite3_mutex_enter(mem.mutex);
mem.disallow++;
sqlite3_mutex_leave(mem.mutex);
}
void sqlite3MallocAllow(void){
assert( mem.mutex );
sqlite3_mutex_enter(mem.mutex);
assert( mem.disallow>0 );
mem.disallow--;
sqlite3_mutex_leave(mem.mutex);
}
#endif /* SQLITE_MEMDEBUG && !SQLITE_OMIT_MEMORY_ALLOCATION */