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Overview
| Comment: | Additional evidence marks on the malloc() implementation. Update the documentation to explain that mallocs are not necessarily 8-byte aligned if the SQLITE_4_BYTE_ALIGNED_MALLOC compile-time option is used. |
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| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
42b4bf9e72501cf228b4086437c76604 |
| User & Date: | drh 2010-09-11 16:15:56.000 |
Context
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2010-09-11
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| 16:25 | Fix a couple of incorrect evidence marks on malloc(). (check-in: f9b5c5cb13 user: drh tags: trunk) | |
| 16:15 | Additional evidence marks on the malloc() implementation. Update the documentation to explain that mallocs are not necessarily 8-byte aligned if the SQLITE_4_BYTE_ALIGNED_MALLOC compile-time option is used. (check-in: 42b4bf9e72 user: drh tags: trunk) | |
| 15:54 | Add assert() statements to demonstrate that memory allocations are always aligned to an 8-byte boundary (unless SQLITE_4_BYTE_ALIGNED_MALLOC is defined). (check-in: 305cc4e6c1 user: drh tags: trunk) | |
Changes
Changes to src/malloc.c.
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/*
** Allocate memory. This routine is like sqlite3_malloc() except that it
** assumes the memory subsystem has already been initialized.
*/
void *sqlite3Malloc(int n){
void *p;
| > | > | 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 |
/*
** Allocate memory. This routine is like sqlite3_malloc() except that it
** assumes the memory subsystem has already been initialized.
*/
void *sqlite3Malloc(int n){
void *p;
if( n<=0 /* IMP: R-65312-04917 */
|| n>=0x7fffff00
){
/* A memory allocation of a number of bytes which is near the maximum
** signed integer value might cause an integer overflow inside of the
** xMalloc(). Hence we limit the maximum size to 0x7fffff00, giving
** 255 bytes of overhead. SQLite itself will never use anything near
** this amount. The only way to reach the limit is with sqlite3_malloc() */
p = 0;
}else if( sqlite3GlobalConfig.bMemstat ){
|
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455 456 457 458 459 460 461 |
}
}
/*
** Free memory previously obtained from sqlite3Malloc().
*/
void sqlite3_free(void *p){
| | | 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 |
}
}
/*
** Free memory previously obtained from sqlite3Malloc().
*/
void sqlite3_free(void *p){
if( p==0 ) return; /* IMP: R-49053-54554 */
assert( sqlite3MemdebugNoType(p, MEMTYPE_DB) );
assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
if( sqlite3GlobalConfig.bMemstat ){
sqlite3_mutex_enter(mem0.mutex);
sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -sqlite3MallocSize(p));
sqlite3StatusAdd(SQLITE_STATUS_MALLOC_COUNT, -1);
sqlite3GlobalConfig.m.xFree(p);
|
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502 503 504 505 506 507 508 |
/*
** Change the size of an existing memory allocation
*/
void *sqlite3Realloc(void *pOld, int nBytes){
int nOld, nNew;
void *pNew;
if( pOld==0 ){
| | | | 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 |
/*
** Change the size of an existing memory allocation
*/
void *sqlite3Realloc(void *pOld, int nBytes){
int nOld, nNew;
void *pNew;
if( pOld==0 ){
return sqlite3Malloc(nBytes); /* IMP: R-28354-25769 */
}
if( nBytes<=0 ){
sqlite3_free(pOld); /* IMP: R-31593-10574 */
return 0;
}
if( nBytes>=0x7fffff00 ){
/* The 0x7ffff00 limit term is explained in comments on sqlite3Malloc() */
return 0;
}
nOld = sqlite3MallocSize(pOld);
|
| ︙ | ︙ |
Changes to src/sqlite.h.in.
| ︙ | ︙ | |||
1943 1944 1945 1946 1947 1948 1949 | ** ^If M is the size of the prior allocation, then min(N,M) bytes ** of the prior allocation are copied into the beginning of buffer returned ** by sqlite3_realloc() and the prior allocation is freed. ** ^If sqlite3_realloc() returns NULL, then the prior allocation ** is not freed. ** ** ^The memory returned by sqlite3_malloc() and sqlite3_realloc() | | > > | 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 | ** ^If M is the size of the prior allocation, then min(N,M) bytes ** of the prior allocation are copied into the beginning of buffer returned ** by sqlite3_realloc() and the prior allocation is freed. ** ^If sqlite3_realloc() returns NULL, then the prior allocation ** is not freed. ** ** ^The memory returned by sqlite3_malloc() and sqlite3_realloc() ** is always aligned to at least an 8 byte boundary, or to a ** 4 byte boundary if the [SQLITE_4_BYTE_ALIGNED_MALLOC] compile-time ** option is used. ** ** In SQLite version 3.5.0 and 3.5.1, it was possible to define ** the SQLITE_OMIT_MEMORY_ALLOCATION which would cause the built-in ** implementation of these routines to be omitted. That capability ** is no longer provided. Only built-in memory allocators can be used. ** ** The Windows OS interface layer calls |
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