Reducing the assumed alignment of struct varlena means that the compiler

tglsfdc · tglsfdc · commit c6f401573f1c · 2008-02-29T17:47:47.000Z
is also licensed to put a local variable declared that way at an unaligned
address.  Which will not work if the variable is then manipulated with
SET_VARSIZE or other macros that assume alignment.  So the previous patch
is not an unalloyed good, but on balance I think it's still a win, since
we have very few places that do that sort of thing.  Fix the one place in
tuptoaster.c that does it.  Per buildfarm results from gypsy_moth
(I'm a bit surprised that only one machine showed a failure).
diff --git a/src/backend/access/heap/tuptoaster.c b/src/backend/access/heap/tuptoaster.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.81.2.1 2008/02/23 19:11:55 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.81.2.2 2008/02/29 17:47:47 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -1093,7 +1093,8 @@ toast_save_datum(Relation rel, Datum value,
 	struct
 	{
 		struct varlena hdr;
-		char		data[TOAST_MAX_CHUNK_SIZE];
+		char		data[TOAST_MAX_CHUNK_SIZE];	/* make struct big enough */
+		int32		align_it;	/* ensure struct is aligned well enough */
 	}			chunk_data;
 	int32		chunk_size;
 	int32		chunk_seq = 0;

Original file line number	Diff line number	Diff line change
`@@ -8,7 +8,7 @@`
`8`	`8`	`*`
`9`	`9`	`*`
`10`	`10`	`* IDENTIFICATION`
`11`		`- * $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.81.2.1 2008/02/23 19:11:55 tgl Exp $`
	`11`	`+ * $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.81.2.2 2008/02/29 17:47:47 tgl Exp $`
`12`	`12`	`*`
`13`	`13`	`*`
`14`	`14`	`* INTERFACE ROUTINES`
`@@ -1093,7 +1093,8 @@ toast_save_datum(Relation rel, Datum value,`
`1093`	`1093`	`struct`
`1094`	`1094`	`{`
`1095`	`1095`	`struct varlena hdr;`
`1096`		`- char data[TOAST_MAX_CHUNK_SIZE];`
	`1096`	`+ char data[TOAST_MAX_CHUNK_SIZE]; /* make struct big enough */`
	`1097`	`+ int32 align_it; /* ensure struct is aligned well enough */`
`1097`	`1098`	`} chunk_data;`
`1098`	`1099`	`int32 chunk_size;`
`1099`	`1100`	`int32 chunk_seq = 0;`