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Code review for palloc0 patch --- avoid dangerous and unnecessary

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practice of evaluating MemSet's arguments multiple times, except for
the special case of newNode(), where we can assume the argument is
a constant sizeof() operator.
Also, add GetMemoryChunkContext() to mcxt.c's API, in preparation for
fixing recent GEQO breakage.
This commit is contained in:
Tom Lane
2002-12-16 16:22:46 +00:00
parent e64c7feb2f
commit 88177f77b1
6 changed files with 160 additions and 52 deletions
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24
src/include/utils/palloc.h
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@ -21,7 +21,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: palloc.h,v 1.23 2002/11/13 00:37:06 momjian Exp $
* $Id: palloc.h,v 1.24 2002/12/16 16:22:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -46,15 +46,25 @@ extern DLLIMPORT MemoryContext CurrentMemoryContext;
* Fundamental memory-allocation operations (more are in utils/memutils.h)
*/
extern void *MemoryContextAlloc(MemoryContext context, Size size);
extern void *MemoryContextAllocPalloc0(MemoryContext context, Size size);
extern void *MemoryContextAllocZero(MemoryContext context, Size size);
extern void *MemoryContextAllocZeroAligned(MemoryContext context, Size size);
#define palloc(sz) MemoryContextAlloc(CurrentMemoryContext, (sz))
/* We assume palloc() is already int-aligned */
#define palloc0(sz) \
( MemSetTest(0, (sz)) ? \
MemoryContextAllocPalloc0(CurrentMemoryContext, (sz)) : \
memset(palloc(sz), 0, (sz)))
#define palloc0(sz) MemoryContextAllocZero(CurrentMemoryContext, (sz))
/*
* The result of palloc() is always word-aligned, so we can skip testing
* alignment of the pointer when deciding which MemSet variant to use.
* Note that this variant does not offer any advantage, and should not be
* used, unless its "sz" argument is a compile-time constant; therefore, the
* issue that it evaluates the argument multiple times isn't a problem in
* practice.
*/
#define palloc0fast(sz) \
( MemSetTest(0, sz) ? \
MemoryContextAllocZeroAligned(CurrentMemoryContext, sz) : \
MemoryContextAllocZero(CurrentMemoryContext, sz) )
extern void pfree(void *pointer);