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7 | 7 | * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group |
8 | 8 | * Portions Copyright (c) 1994, Regents of the University of California |
9 | 9 | * |
10 | | - * $PostgreSQL: pgsql/src/include/storage/bufpage.h,v 1.57 2003/12/11 21:21:55 tgl Exp $ |
| 10 | + * $PostgreSQL: pgsql/src/include/storage/bufpage.h,v 1.58 2004/06/05 17:42:46 tgl Exp $ |
11 | 11 | * |
12 | 12 | *------------------------------------------------------------------------- |
13 | 13 | */ |
@@ -283,13 +283,14 @@ typedef PageHeaderData *PageHeader; |
283 | 283 | *Since offset numbers are 1-based, this is also the number |
284 | 284 | *of items on the page. |
285 | 285 | * |
286 | | - *NOTE:to ensure sane behaviorif the page is not initialized |
287 | | - *(pd_lower == 0), cast the unsigned values to int before dividing. |
288 | | - *That way we get -1 or so, not a huge positive number... |
| 286 | + *NOTE: if the page is not initialized (pd_lower == 0), we must |
| 287 | + *return zero to ensure sane behavior. Accept double evaluation |
| 288 | + *of the argument so that we can ensure this. |
289 | 289 | */ |
290 | 290 | #definePageGetMaxOffsetNumber(page) \ |
291 | | -(((int) (((PageHeader) (page))->pd_lower - SizeOfPageHeaderData)) \ |
292 | | - / ((int) sizeof(ItemIdData))) |
| 291 | +(((PageHeader) (page))->pd_lower <= SizeOfPageHeaderData ? 0 : \ |
| 292 | + ((((PageHeader) (page))->pd_lower - SizeOfPageHeaderData) \ |
| 293 | + / sizeof(ItemIdData))) |
293 | 294 |
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294 | 295 | #definePageGetLSN(page) \ |
295 | 296 | (((PageHeader) (page))->pd_lsn) |
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