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Whether platform malloc(0) returns NULL has nothing to do with whether 

platform realloc(p, 0) returns NULL, so MALLOC_ZERO_RETURNS_NULL can
be correctly undefined yet realloc(p, 0) can return NULL anyway.

Prevent realloc(p, 0) doing free(p) and returning NULL via a different
hack.  Would probably be better to get rid of MALLOC_ZERO_RETURNS_NULL
entirely.

Bugfix candidate.
This commit is contained in:
Tim Peters 2002-03-02 08:43:19 +00:00
parent b77d343bc8
commit a5d78cc208
3 changed files with 24 additions and 14 deletions
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19
Include/pymem.h
View File

@ -111,13 +111,18 @@ extern DL_IMPORT(void) PyMem_Free(void *);
/* Macros */
#define PyMem_NEW(type, n) \
( (type *) PyMem_MALLOC(_PyMem_EXTRA + (n) * sizeof(type)) )
#define PyMem_RESIZE(p, type, n) \
if ((p) == NULL) \
(p) = (type *)(PyMem_MALLOC( \
_PyMem_EXTRA + (n) * sizeof(type))); \
else \
(p) = (type *)(PyMem_REALLOC((p), \
_PyMem_EXTRA + (n) * sizeof(type)))
/* See comment near MALLOC_ZERO_RETURNS_NULL in pyport.h. */
#define PyMem_RESIZE(p, type, n) \
do { \
size_t _sum = (n) * sizeof(type); \
if (!_sum) \
_sum = 1; \
(p) = (type *)((p) ? \
PyMem_REALLOC(p, _sum) : \
PyMem_MALLOC(_sum)); \
} while (0)
#define PyMem_DEL(p) PyMem_FREE(p)
/* PyMem_XDEL is deprecated. To avoid the call when p is NULL,

12
Include/pyport.h
View File

@ -366,8 +366,16 @@ extern double hypot(double, double);
#endif
#ifdef MALLOC_ZERO_RETURNS_NULL
/* XXX Always allocate one extra byte, since some malloc's return NULL
XXX for malloc(0) or realloc(p, 0). */
/* Allocate an extra byte if the platform malloc(0) returns NULL.
Caution: this bears no relation to whether realloc(p, 0) returns NULL
when p != NULL. Even on platforms where malloc(0) does not return NULL,
realloc(p, 0) may act like free(p) and return NULL. Examples include
Windows, and Python's own obmalloc.c (as of 2-Mar-2002). For whatever
reason, our docs promise that PyMem_Realloc(p, 0) won't act like
free(p) or return NULL, so realloc() calls may have to be hacked
too, but MALLOC_ZERO_RETURNS_NULL's state is irrelevant to realloc (it
needs a different hack).
*/
#define _PyMem_EXTRA 1
#else
#define _PyMem_EXTRA 0

7
Objects/object.c
View File

@ -1894,11 +1894,8 @@ PyMem_Malloc(size_t nbytes)
void *
PyMem_Realloc(void *p, size_t nbytes)
{
#if _PyMem_EXTRA > 0
if (nbytes == 0)
nbytes = _PyMem_EXTRA;
#endif
return PyMem_REALLOC(p, nbytes);
/* See comment near MALLOC_ZERO_RETURNS_NULL in pyport.h. */
return PyMem_REALLOC(p, nbytes ? nbytes : 1);
}
void