diff options
Diffstat (limited to 'src/include/postgres.h')
| -rw-r--r-- | src/include/postgres.h | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/src/include/postgres.h b/src/include/postgres.h index f9164e3cca7..75fe2a0272e 100644 --- a/src/include/postgres.h +++ b/src/include/postgres.h @@ -10,7 +10,7 @@ * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group * Portions Copyright (c) 1995, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/postgres.h,v 1.75 2006/07/13 16:49:18 momjian Exp $ + * $PostgreSQL: pgsql/src/include/postgres.h,v 1.75.2.1 2008/03/25 19:31:31 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -123,13 +123,18 @@ 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) @@ -143,10 +148,11 @@ 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 |