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1/*
2** 2007 August 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** This file contains the C functions that implement a memory
13** allocation subsystem for use by SQLite.
14**
15** $Id: mem2.c,v 1.14 2007/10/03 08:46:45 danielk1977 Exp $
16*/
17
18/*
19** This version of the memory allocator is used only if the
20** SQLITE_MEMDEBUG macro is defined and SQLITE_OMIT_MEMORY_ALLOCATION
21** is not defined.
22*/
23#if defined(SQLITE_MEMDEBUG) && !defined(SQLITE_OMIT_MEMORY_ALLOCATION)
24
25/*
26** We will eventually construct multiple memory allocation subsystems
27** suitable for use in various contexts:
28**
29** * Normal multi-threaded builds
30** * Normal single-threaded builds
31** * Debugging builds
32**
33** This version is suitable for use in debugging builds.
34**
35** Features:
36**
37** * Every allocate has guards at both ends.
38** * New allocations are initialized with randomness
39** * Allocations are overwritten with randomness when freed
40** * Optional logs of malloc activity generated
41** * Summary of outstanding allocations with backtraces to the
42** point of allocation.
43** * The ability to simulate memory allocation failure
44*/
45#include "sqliteInt.h"
46#include <stdio.h>
47
48/*
49** The backtrace functionality is only available with GLIBC
50*/
51#ifdef __GLIBC__
52 extern int backtrace(void**,int);
53 extern void backtrace_symbols_fd(void*const*,int,int);
54#else
55# define backtrace(A,B) 0
56# define backtrace_symbols_fd(A,B,C)
57#endif
58
59/*
60** Each memory allocation looks like this:
61**
62** ------------------------------------------------------------------------
63** | Title | backtrace pointers | MemBlockHdr | allocation | EndGuard |
64** ------------------------------------------------------------------------
65**
66** The application code sees only a pointer to the allocation. We have
67** to back up from the allocation pointer to find the MemBlockHdr. The
68** MemBlockHdr tells us the size of the allocation and the number of
69** backtrace pointers. There is also a guard word at the end of the
70** MemBlockHdr.
71*/
72struct MemBlockHdr {
73 struct MemBlockHdr *pNext, *pPrev; /* Linked list of all unfreed memory */
74 int iSize; /* Size of this allocation */
75 char nBacktrace; /* Number of backtraces on this alloc */
76 char nBacktraceSlots; /* Available backtrace slots */
77 short nTitle; /* Bytes of title; includes '\0' */
78 int iForeGuard; /* Guard word for sanity */
79};
80
81/*
82** Guard words
83*/
84#define FOREGUARD 0x80F5E153
85#define REARGUARD 0xE4676B53
86
87/*
88** All of the static variables used by this module are collected
89** into a single structure named "mem". This is to keep the
90** static variables organized and to reduce namespace pollution
91** when this module is combined with other in the amalgamation.
92*/
93static struct {
94 /*
95 ** The alarm callback and its arguments. The mem.mutex lock will
96 ** be held while the callback is running. Recursive calls into
97 ** the memory subsystem are allowed, but no new callbacks will be
98 ** issued. The alarmBusy variable is set to prevent recursive
99 ** callbacks.
100 */
101 sqlite3_int64 alarmThreshold;
102 void (*alarmCallback)(void*, sqlite3_int64, int);
103 void *alarmArg;
104 int alarmBusy;
105
106 /*
107 ** Mutex to control access to the memory allocation subsystem.
108 */
109 sqlite3_mutex *mutex;
110
111 /*
112 ** Current allocation and high-water mark.
113 */
114 sqlite3_int64 nowUsed;
115 sqlite3_int64 mxUsed;
116
117 /*
118 ** Head and tail of a linked list of all outstanding allocations
119 */
120 struct MemBlockHdr *pFirst;
121 struct MemBlockHdr *pLast;
122
123 /*
124 ** The number of levels of backtrace to save in new allocations.
125 */
126 int nBacktrace;
127
128 /*
129 ** Title text to insert in front of each block
130 */
131 int nTitle; /* Bytes of zTitle to save. Includes '\0' and padding */
132 char zTitle[100]; /* The title text */
133
134 /*
135 ** These values are used to simulate malloc failures. When
136 ** iFail is 1, simulate a malloc failures and reset the value
137 ** to iReset.
138 */
139 int iFail; /* Decrement and fail malloc when this is 1 */
140 int iReset; /* When malloc fails set iiFail to this value */
141 int iFailCnt; /* Number of failures */
142 int iBenignFailCnt; /* Number of benign failures */
143 int iNextIsBenign; /* True if the next call to malloc may fail benignly */
144 int iIsBenign; /* All malloc calls may fail benignly */
145
146 /*
147 ** sqlite3MallocDisallow() increments the following counter.
148 ** sqlite3MallocAllow() decrements it.
149 */
150 int disallow; /* Do not allow memory allocation */
151
152
153} mem;
154
155
156/*
157** Enter the mutex mem.mutex. Allocate it if it is not already allocated.
158*/
159static void enterMem(void){
160 if( mem.mutex==0 ){
161 mem.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM);
162 }
163 sqlite3_mutex_enter(mem.mutex);
164}
165
166/*
167** Return the amount of memory currently checked out.
168*/
169sqlite3_int64 sqlite3_memory_used(void){
170 sqlite3_int64 n;
171 enterMem();
172 n = mem.nowUsed;
173 sqlite3_mutex_leave(mem.mutex);
174 return n;
175}
176
177/*
178** Return the maximum amount of memory that has ever been
179** checked out since either the beginning of this process
180** or since the most recent reset.
181*/
182sqlite3_int64 sqlite3_memory_highwater(int resetFlag){
183 sqlite3_int64 n;
184 enterMem();
185 n = mem.mxUsed;
186 if( resetFlag ){
187 mem.mxUsed = mem.nowUsed;
188 }
189 sqlite3_mutex_leave(mem.mutex);
190 return n;
191}
192
193/*
194** Change the alarm callback
195*/
196int sqlite3_memory_alarm(
197 void(*xCallback)(void *pArg, sqlite3_int64 used, int N),
198 void *pArg,
199 sqlite3_int64 iThreshold
200){
201 enterMem();
202 mem.alarmCallback = xCallback;
203 mem.alarmArg = pArg;
204 mem.alarmThreshold = iThreshold;
205 sqlite3_mutex_leave(mem.mutex);
206 return SQLITE_OK;
207}
208
209/*
210** Trigger the alarm
211*/
212static void sqlite3MemsysAlarm(int nByte){
213 void (*xCallback)(void*,sqlite3_int64,int);
214 sqlite3_int64 nowUsed;
215 void *pArg;
216 if( mem.alarmCallback==0 || mem.alarmBusy ) return;
217 mem.alarmBusy = 1;
218 xCallback = mem.alarmCallback;
219 nowUsed = mem.nowUsed;
220 pArg = mem.alarmArg;
221 sqlite3_mutex_leave(mem.mutex);
222 xCallback(pArg, nowUsed, nByte);
223 sqlite3_mutex_enter(mem.mutex);
224 mem.alarmBusy = 0;
225}
226
227/*
228** Given an allocation, find the MemBlockHdr for that allocation.
229**
230** This routine checks the guards at either end of the allocation and
231** if they are incorrect it asserts.
232*/
233static struct MemBlockHdr *sqlite3MemsysGetHeader(void *pAllocation){
234 struct MemBlockHdr *p;
235 int *pInt;
236
237 p = (struct MemBlockHdr*)pAllocation;
238 p--;
239 assert( p->iForeGuard==FOREGUARD );
240 assert( (p->iSize & 3)==0 );
241 pInt = (int*)pAllocation;
242 assert( pInt[p->iSize/sizeof(int)]==REARGUARD );
243 return p;
244}
245
246/*
247** This routine is called once the first time a simulated memory
248** failure occurs. The sole purpose of this routine is to provide
249** a convenient place to set a debugger breakpoint when debugging
250** errors related to malloc() failures.
251*/
252static void sqlite3MemsysFailed(void){
253 mem.iFailCnt = 0;
254 mem.iBenignFailCnt = 0;
255}
256
257/*
258** Allocate nByte bytes of memory.
259*/
260void *sqlite3_malloc(int nByte){
261 struct MemBlockHdr *pHdr;
262 void **pBt;
263 char *z;
264 int *pInt;
265 void *p = 0;
266 int totalSize;
267
268 if( nByte>0 ){
269 enterMem();
270 assert( mem.disallow==0 );
271 if( mem.alarmCallback!=0 && mem.nowUsed+nByte>=mem.alarmThreshold ){
272 sqlite3MemsysAlarm(nByte);
273 }
274 nByte = (nByte+3)&~3;
275 totalSize = nByte + sizeof(*pHdr) + sizeof(int) +
276 mem.nBacktrace*sizeof(void*) + mem.nTitle;
277 if( mem.iFail>0 ){
278 if( mem.iFail==1 ){
279 p = 0;
280 mem.iFail = mem.iReset;
281 if( mem.iFailCnt==0 ){
282 sqlite3MemsysFailed(); /* A place to set a breakpoint */
283 }
284 mem.iFailCnt++;
285 if( mem.iNextIsBenign || mem.iIsBenign ){
286 mem.iBenignFailCnt++;
287 }
288 }else{
289 p = malloc(totalSize);
290 mem.iFail--;
291 }
292 }else{
293 p = malloc(totalSize);
294 if( p==0 ){
295 sqlite3MemsysAlarm(nByte);
296 p = malloc(totalSize);
297 }
298 }
299 if( p ){
300 z = p;
301 pBt = (void**)&z[mem.nTitle];
302 pHdr = (struct MemBlockHdr*)&pBt[mem.nBacktrace];
303 pHdr->pNext = 0;
304 pHdr->pPrev = mem.pLast;
305 if( mem.pLast ){
306 mem.pLast->pNext = pHdr;
307 }else{
308 mem.pFirst = pHdr;
309 }
310 mem.pLast = pHdr;
311 pHdr->iForeGuard = FOREGUARD;
312 pHdr->nBacktraceSlots = mem.nBacktrace;
313 pHdr->nTitle = mem.nTitle;
314 if( mem.nBacktrace ){
315 void *aAddr[40];
316 pHdr->nBacktrace = backtrace(aAddr, mem.nBacktrace+1)-1;
317 memcpy(pBt, &aAddr[1], pHdr->nBacktrace*sizeof(void*));
318 }else{
319 pHdr->nBacktrace = 0;
320 }
321 if( mem.nTitle ){
322 memcpy(z, mem.zTitle, mem.nTitle);
323 }
324 pHdr->iSize = nByte;
325 pInt = (int*)&pHdr[1];
326 pInt[nByte/sizeof(int)] = REARGUARD;
327 memset(pInt, 0x65, nByte);
328 mem.nowUsed += nByte;
329 if( mem.nowUsed>mem.mxUsed ){
330 mem.mxUsed = mem.nowUsed;
331 }
332 p = (void*)pInt;
333 }
334 sqlite3_mutex_leave(mem.mutex);
335 }
336 mem.iNextIsBenign = 0;
337 return p;
338}
339
340/*
341** Free memory.
342*/
343void sqlite3_free(void *pPrior){
344 struct MemBlockHdr *pHdr;
345 void **pBt;
346 char *z;
347 if( pPrior==0 ){
348 return;
349 }
350 assert( mem.mutex!=0 );
351 pHdr = sqlite3MemsysGetHeader(pPrior);
352 pBt = (void**)pHdr;
353 pBt -= pHdr->nBacktraceSlots;
354 sqlite3_mutex_enter(mem.mutex);
355 mem.nowUsed -= pHdr->iSize;
356 if( pHdr->pPrev ){
357 assert( pHdr->pPrev->pNext==pHdr );
358 pHdr->pPrev->pNext = pHdr->pNext;
359 }else{
360 assert( mem.pFirst==pHdr );
361 mem.pFirst = pHdr->pNext;
362 }
363 if( pHdr->pNext ){
364 assert( pHdr->pNext->pPrev==pHdr );
365 pHdr->pNext->pPrev = pHdr->pPrev;
366 }else{
367 assert( mem.pLast==pHdr );
368 mem.pLast = pHdr->pPrev;
369 }
370 z = (char*)pBt;
371 z -= pHdr->nTitle;
372 memset(z, 0x2b, sizeof(void*)*pHdr->nBacktraceSlots + sizeof(*pHdr) +
373 pHdr->iSize + sizeof(int) + pHdr->nTitle);
374 free(z);
375 sqlite3_mutex_leave(mem.mutex);
376}
377
378/*
379** Change the size of an existing memory allocation.
380**
381** For this debugging implementation, we *always* make a copy of the
382** allocation into a new place in memory. In this way, if the
383** higher level code is using pointer to the old allocation, it is
384** much more likely to break and we are much more liking to find
385** the error.
386*/
387void *sqlite3_realloc(void *pPrior, int nByte){
388 struct MemBlockHdr *pOldHdr;
389 void *pNew;
390 if( pPrior==0 ){
391 return sqlite3_malloc(nByte);
392 }
393 if( nByte<=0 ){
394 sqlite3_free(pPrior);
395 return 0;
396 }
397 assert( mem.disallow==0 );
398 pOldHdr = sqlite3MemsysGetHeader(pPrior);
399 pNew = sqlite3_malloc(nByte);
400 if( pNew ){
401 memcpy(pNew, pPrior, nByte<pOldHdr->iSize ? nByte : pOldHdr->iSize);
402 if( nByte>pOldHdr->iSize ){
403 memset(&((char*)pNew)[pOldHdr->iSize], 0x2b, nByte - pOldHdr->iSize);
404 }
405 sqlite3_free(pPrior);
406 }
407 return pNew;
408}
409
410/*
411** Set the number of backtrace levels kept for each allocation.
412** A value of zero turns of backtracing. The number is always rounded
413** up to a multiple of 2.
414*/
415void sqlite3_memdebug_backtrace(int depth){
416 if( depth<0 ){ depth = 0; }
417 if( depth>20 ){ depth = 20; }
418 depth = (depth+1)&0xfe;
419 mem.nBacktrace = depth;
420}
421
422/*
423** Set the title string for subsequent allocations.
424*/
425void sqlite3_memdebug_settitle(const char *zTitle){
426 int n = strlen(zTitle) + 1;
427 enterMem();
428 if( n>=sizeof(mem.zTitle) ) n = sizeof(mem.zTitle)-1;
429 memcpy(mem.zTitle, zTitle, n);
430 mem.zTitle[n] = 0;
431 mem.nTitle = (n+3)&~3;
432 sqlite3_mutex_leave(mem.mutex);
433}
434
435/*
436** Open the file indicated and write a log of all unfreed memory
437** allocations into that log.
438*/
439void sqlite3_memdebug_dump(const char *zFilename){
440 FILE *out;
441 struct MemBlockHdr *pHdr;
442 void **pBt;
443 out = fopen(zFilename, "w");
444 if( out==0 ){
445 fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
446 zFilename);
447 return;
448 }
449 for(pHdr=mem.pFirst; pHdr; pHdr=pHdr->pNext){
450 char *z = (char*)pHdr;
451 z -= pHdr->nBacktraceSlots*sizeof(void*) + pHdr->nTitle;
452 fprintf(out, "**** %d bytes at %p from %s ****\n",
453 pHdr->iSize, &pHdr[1], pHdr->nTitle ? z : "???");
454 if( pHdr->nBacktrace ){
455 fflush(out);
456 pBt = (void**)pHdr;
457 pBt -= pHdr->nBacktraceSlots;
458 backtrace_symbols_fd(pBt, pHdr->nBacktrace, fileno(out));
459 fprintf(out, "\n");
460 }
461 }
462 fclose(out);
463}
464
465/*
466** This routine is used to simulate malloc failures.
467**
468** After calling this routine, there will be iFail successful
469** memory allocations and then a failure. If iRepeat is 1
470** all subsequent memory allocations will fail. If iRepeat is
471** 0, only a single allocation will fail. If iRepeat is negative
472** then the previous setting for iRepeat is unchanged.
473**
474** Each call to this routine overrides the previous. To disable
475** the simulated allocation failure mechanism, set iFail to -1.
476**
477** This routine returns the number of simulated failures that have
478** occurred since the previous call.
479*/
480int sqlite3_memdebug_fail(int iFail, int iRepeat, int *piBenign){
481 int n = mem.iFailCnt;
482 if( piBenign ){
483 *piBenign = mem.iBenignFailCnt;
484 }
485 mem.iFail = iFail+1;
486 if( iRepeat>=0 ){
487 mem.iReset = iRepeat;
488 }
489 mem.iFailCnt = 0;
490 mem.iBenignFailCnt = 0;
491 return n;
492}
493
494int sqlite3_memdebug_pending(){
495 return (mem.iFail-1);
496}
497
498/*
499** The following three functions are used to indicate to the test
500** infrastructure which malloc() calls may fail benignly without
501** affecting functionality. This can happen when resizing hash tables
502** (failing to resize a hash-table is a performance hit, but not an
503** error) or sometimes during a rollback operation.
504**
505** If the argument is true, sqlite3MallocBenignFailure() indicates that the
506** next call to allocate memory may fail benignly.
507**
508** If sqlite3MallocEnterBenignBlock() is called with a non-zero argument,
509** then all memory allocations requested before the next call to
510** sqlite3MallocLeaveBenignBlock() may fail benignly.
511*/
512void sqlite3MallocBenignFailure(int isBenign){
513 if( isBenign ){
514 mem.iNextIsBenign = 1;
515 }
516}
517void sqlite3MallocEnterBenignBlock(int isBenign){
518 if( isBenign ){
519 mem.iIsBenign = 1;
520 }
521}
522void sqlite3MallocLeaveBenignBlock(){
523 mem.iIsBenign = 0;
524}
525
526/*
527** The following two routines are used to assert that no memory
528** allocations occur between one call and the next. The use of
529** these routines does not change the computed results in any way.
530** These routines are like asserts.
531*/
532void sqlite3MallocDisallow(void){
533 assert( mem.mutex!=0 );
534 sqlite3_mutex_enter(mem.mutex);
535 mem.disallow++;
536 sqlite3_mutex_leave(mem.mutex);
537}
538void sqlite3MallocAllow(void){
539 assert( mem.mutex );
540 sqlite3_mutex_enter(mem.mutex);
541 assert( mem.disallow>0 );
542 mem.disallow--;
543 sqlite3_mutex_leave(mem.mutex);
544}
545
546#endif /* SQLITE_MEMDEBUG && !SQLITE_OMIT_MEMORY_ALLOCATION */