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Adjust DatumGetBool macro so that it isn't fooled by garbage in the Datum

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to the left of the actual bool value.  While in most cases there won't be
any, our support for old-style user-defined functions violates the C spec
to the extent of calling functions that might return char or short through
a function pointer declared to return "char *", which we then coerce to
Datum.  It is not surprising that the result might contain garbage
high-order bits ... what is surprising is that we didn't see such cases
long ago.  Per report from Magnus.
This commit is contained in:
Tom Lane 2007-03-23 20:24:41 +00:00
parent 547b6e537a
commit 23a41573c4
1 changed files with 11 additions and 5 deletions
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16
src/include/postgres.h
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@ -10,7 +10,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1995, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/postgres.h,v 1.77 2007/02/27 23:48:09 tgl Exp $
* $PostgreSQL: pgsql/src/include/postgres.h,v 1.78 2007/03/23 20:24:41 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -125,13 +125,18 @@ typedef struct varattrib
*
* sizeof(short) == 2
*
* If your machine meets these requirements, Datums should also be checked
* to see if the positioning is correct.
* When a type narrower than Datum is stored in a Datum, we place it in the
* low-order bits and are careful that the DatumGetXXX macro for it discards
* the unused high-order bits (as opposed to, say, assuming they are zero).
* This is needed to support old-style user-defined functions, since depending
* on architecture and compiler, the return value of a function returning char
* or short may contain garbage when called as if it returned Datum.
*/
typedef unsigned long Datum; /* XXX sizeof(long) >= sizeof(void *) */
#define SIZEOF_DATUM SIZEOF_UNSIGNED_LONG
typedef Datum *DatumPtr;
#define GET_1_BYTE(datum) (((Datum) (datum)) & 0x000000ff)
@ -145,10 +150,11 @@ typedef Datum *DatumPtr;
* DatumGetBool
* Returns boolean value of a datum.
*
* Note: any nonzero value will be considered TRUE.
* Note: any nonzero value will be considered TRUE, but we ignore bits to
* the left of the width of bool, per comment above.
*/
#define DatumGetBool(X) ((bool) (((Datum) (X)) != 0))
#define DatumGetBool(X) ((bool) (((bool) (X)) != 0))
/*
* BoolGetDatum