Code review for palloc0 patch --- avoid dangerous and unnecessary
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
parent
e64c7feb2f
commit
88177f77b1
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@ -9,7 +9,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/nodes/nodes.c,v 1.18 2002/11/10 02:17:25 momjian Exp $
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* $Header: /cvsroot/pgsql/src/backend/nodes/nodes.c,v 1.19 2002/12/16 16:22:46 tgl Exp $
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*
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* HISTORY
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* Andrew Yu Oct 20, 1994 file creation
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@ -17,16 +17,11 @@
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "nodes/nodes.h"
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/*
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* newNode -
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* create a new node of the specified size and tag the node with the
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* specified tag.
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*
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* !WARNING!: Avoid using newNode directly. You should be using the
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* macro makeNode. eg. to create a Resdom node, use makeNode(Resdom)
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*
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* Support for newNode() macro
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*/
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Node *newNodeMacroHolder;
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Node *newNodeMacroHolder;
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@ -14,7 +14,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/utils/mmgr/mcxt.c,v 1.37 2002/12/15 21:01:34 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/utils/mmgr/mcxt.c,v 1.38 2002/12/16 16:22:46 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -257,6 +257,35 @@ GetMemoryChunkSpace(void *pointer)
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pointer);
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}
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/*
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* GetMemoryChunkContext
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* Given a currently-allocated chunk, determine the context
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* it belongs to.
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*/
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MemoryContext
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GetMemoryChunkContext(void *pointer)
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{
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StandardChunkHeader *header;
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/*
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* Try to detect bogus pointers handed to us, poorly though we can.
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* Presumably, a pointer that isn't MAXALIGNED isn't pointing at an
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* allocated chunk.
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*/
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Assert(pointer != NULL);
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Assert(pointer == (void *) MAXALIGN(pointer));
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/*
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* OK, it's probably safe to look at the chunk header.
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*/
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header = (StandardChunkHeader *)
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((char *) pointer - STANDARDCHUNKHEADERSIZE);
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AssertArg(MemoryContextIsValid(header->context));
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return header->context;
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}
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/*
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* MemoryContextStats
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* Print statistics about the named context and all its descendants.
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@ -453,25 +482,52 @@ MemoryContextAlloc(MemoryContext context, Size size)
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}
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/*
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* MemoryContextAllocPalloc0
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* MemoryContextAllocZero
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* Like MemoryContextAlloc, but clears allocated memory
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*
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* We could just call MemoryContextAlloc then clear the memory, but this
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* function is called too many times, so we have a separate version.
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* is a very common combination, so we provide the combined operation.
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*/
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void *
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MemoryContextAllocPalloc0(MemoryContext context, Size size)
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MemoryContextAllocZero(MemoryContext context, Size size)
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{
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void *ret;
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AssertArg(MemoryContextIsValid(context));
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if (!AllocSizeIsValid(size))
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elog(ERROR, "MemoryContextAllocZero: invalid request size %lu",
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elog(ERROR, "MemoryContextAlloc: invalid request size %lu",
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(unsigned long) size);
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ret = (*context->methods->alloc) (context, size);
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MemSetAligned(ret, 0, size);
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return ret;
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}
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/*
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* MemoryContextAllocZeroAligned
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* MemoryContextAllocZero where length is suitable for MemSetLoop
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*
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* This might seem overly specialized, but it's not because newNode()
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* is so often called with compile-time-constant sizes.
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*/
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void *
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MemoryContextAllocZeroAligned(MemoryContext context, Size size)
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{
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void *ret;
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AssertArg(MemoryContextIsValid(context));
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if (!AllocSizeIsValid(size))
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elog(ERROR, "MemoryContextAlloc: invalid request size %lu",
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(unsigned long) size);
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ret = (*context->methods->alloc) (context, size);
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MemSetLoop(ret, 0, size);
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return ret;
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}
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@ -12,7 +12,7 @@
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* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: c.h,v 1.133 2002/12/05 04:04:48 momjian Exp $
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* $Id: c.h,v 1.134 2002/12/16 16:22:46 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -579,38 +579,78 @@ typedef NameData *Name;
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* memset() functions. More research needs to be done, perhaps with
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* platform-specific MEMSET_LOOP_LIMIT values or tests in configure.
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*
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* MemSet has been split into two parts so MemSetTest can be optimized
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* away for constant 'val' and 'len'. This is used by palloc0().
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*
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* Note, arguments are evaluated more than once.
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*
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* bjm 2002-10-08
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*/
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#define MemSet(start, val, len) \
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do \
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{ \
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int32 * _start = (int32 *) (start); \
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int _val = (val); \
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Size _len = (len); \
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\
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if ((((long) _start) & INT_ALIGN_MASK) == 0 && \
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(_len & INT_ALIGN_MASK) == 0 && \
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_val == 0 && \
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_len <= MEMSET_LOOP_LIMIT) \
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{ \
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int32 * _stop = (int32 *) ((char *) _start + _len); \
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while (_start < _stop) \
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*_start++ = 0; \
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} \
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else \
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memset((char *) _start, _val, _len); \
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} while (0)
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#define MEMSET_LOOP_LIMIT 1024
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/*
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* MemSetAligned is the same as MemSet except it omits the test to see if
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* "start" is word-aligned. This is okay to use if the caller knows a-priori
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* that the pointer is suitably aligned (typically, because he just got it
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* from palloc(), which always delivers a max-aligned pointer).
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*/
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#define MemSetAligned(start, val, len) \
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do \
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{ \
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int32 * _start = (int32 *) (start); \
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int _val = (val); \
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Size _len = (len); \
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\
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if ((_len & INT_ALIGN_MASK) == 0 && \
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_val == 0 && \
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_len <= MEMSET_LOOP_LIMIT) \
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{ \
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int32 * _stop = (int32 *) ((char *) _start + _len); \
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while (_start < _stop) \
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*_start++ = 0; \
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} \
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else \
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memset((char *) _start, _val, _len); \
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} while (0)
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/*
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* MemSetTest/MemSetLoop are a variant version that allow all the tests in
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* MemSet to be done at compile time in cases where "val" and "len" are
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* constants *and* we know the "start" pointer must be word-aligned.
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* If MemSetTest succeeds, then it is okay to use MemSetLoop, otherwise use
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* MemSetAligned. Beware of multiple evaluations of the arguments when using
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* this approach.
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*/
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#define MemSetTest(val, len) \
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( ((len) & INT_ALIGN_MASK) == 0 && \
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(len) <= MEMSET_LOOP_LIMIT && \
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(val) == 0 )
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#define MemSetLoop(start, val, len) \
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do \
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{ \
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int32 * _start = (int32 *) (start); \
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int32 * _stop = (int32 *) ((char *) _start + (len)); \
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\
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while (_start < _stop) \
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*_start++ = 0; \
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} while (0)
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#define MemSet(start, val, len) \
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do \
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{ \
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if (MemSetTest(val, len) && ((long)(start) & INT_ALIGN_MASK) == 0 ) \
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MemSetLoop(start, val, len); \
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else \
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memset((char *)(start), (val), (len)); \
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} while (0)
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#define MEMSET_LOOP_LIMIT 1024
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do \
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{ \
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int32 * _start = (int32 *) (start); \
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int32 * _stop = (int32 *) ((char *) _start + (Size) (len)); \
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\
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while (_start < _stop) \
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*_start++ = 0; \
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} while (0)
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/* ----------------------------------------------------------------
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: nodes.h,v 1.133 2002/12/14 00:17:59 tgl Exp $
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* $Id: nodes.h,v 1.134 2002/12/16 16:22:46 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -293,9 +293,16 @@ typedef struct Node
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#define nodeTag(nodeptr) (((Node*)(nodeptr))->type)
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/*
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* newNode -
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* create a new node of the specified size and tag the node with the
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* specified tag.
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*
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* !WARNING!: Avoid using newNode directly. You should be using the
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* macro makeNode. eg. to create a Query node, use makeNode(Query)
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*
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* There is no way to dereference the palloc'ed pointer to assign the
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* tag, and return the pointer itself, so we need a holder variable.
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* Fortunately, this function isn't recursive so we just define
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* tag, and also return the pointer itself, so we need a holder variable.
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* Fortunately, this macro isn't recursive so we just define
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* a global variable for this purpose.
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*/
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extern Node *newNodeMacroHolder;
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@ -303,8 +310,7 @@ extern Node *newNodeMacroHolder;
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#define newNode(size, tag) \
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( \
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AssertMacro((size) >= sizeof(Node)), /* need the tag, at least */ \
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\
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newNodeMacroHolder = (Node *) palloc0(size), \
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newNodeMacroHolder = (Node *) palloc0fast(size), \
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newNodeMacroHolder->type = (tag), \
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newNodeMacroHolder \
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)
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@ -10,7 +10,7 @@
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* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: memutils.h,v 1.49 2002/12/15 21:01:34 tgl Exp $
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* $Id: memutils.h,v 1.50 2002/12/16 16:22:46 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -83,6 +83,7 @@ extern void MemoryContextResetChildren(MemoryContext context);
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extern void MemoryContextDeleteChildren(MemoryContext context);
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extern void MemoryContextResetAndDeleteChildren(MemoryContext context);
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extern Size GetMemoryChunkSpace(void *pointer);
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extern MemoryContext GetMemoryChunkContext(void *pointer);
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extern void MemoryContextStats(MemoryContext context);
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#ifdef MEMORY_CONTEXT_CHECKING
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@ -21,7 +21,7 @@
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* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: palloc.h,v 1.23 2002/11/13 00:37:06 momjian Exp $
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* $Id: palloc.h,v 1.24 2002/12/16 16:22:46 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -46,15 +46,25 @@ extern DLLIMPORT MemoryContext CurrentMemoryContext;
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* Fundamental memory-allocation operations (more are in utils/memutils.h)
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*/
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extern void *MemoryContextAlloc(MemoryContext context, Size size);
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extern void *MemoryContextAllocPalloc0(MemoryContext context, Size size);
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extern void *MemoryContextAllocZero(MemoryContext context, Size size);
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extern void *MemoryContextAllocZeroAligned(MemoryContext context, Size size);
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#define palloc(sz) MemoryContextAlloc(CurrentMemoryContext, (sz))
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/* We assume palloc() is already int-aligned */
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#define palloc0(sz) \
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( MemSetTest(0, (sz)) ? \
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MemoryContextAllocPalloc0(CurrentMemoryContext, (sz)) : \
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memset(palloc(sz), 0, (sz)))
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#define palloc0(sz) MemoryContextAllocZero(CurrentMemoryContext, (sz))
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/*
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* The result of palloc() is always word-aligned, so we can skip testing
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* alignment of the pointer when deciding which MemSet variant to use.
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* Note that this variant does not offer any advantage, and should not be
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* used, unless its "sz" argument is a compile-time constant; therefore, the
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* issue that it evaluates the argument multiple times isn't a problem in
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* practice.
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*/
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#define palloc0fast(sz) \
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( MemSetTest(0, sz) ? \
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MemoryContextAllocZeroAligned(CurrentMemoryContext, sz) : \
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MemoryContextAllocZero(CurrentMemoryContext, sz) )
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extern void pfree(void *pointer);
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