Install a workaround for a longstanding gcc bug that allows SIGFPE traps

to occur for division by zero, even though the code is carefully avoiding
that.  All available evidence is that the only functions affected are
int24div, int48div, and int28div, so patch just those three functions to
include a "return" after the ereport() call.

Backpatch to 8.4 so that the fix can be tested in production builds.
For older branches our recommendation will continue to be to use -O1
on affected platforms (which are mostly non-mainstream anyway).

src/backend/utils/adt/int.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/int.c,v 1.84 2009/01/01 17:23:49 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/int.c,v 1.85 2009/09/03 18:48:14 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -950,9 +950,14 @@ int24div(PG_FUNCTION_ARGS)
 	int32		arg2 = PG_GETARG_INT32(1);
 
 	if (arg2 == 0)
+	{
 		ereport(ERROR,
 				(errcode(ERRCODE_DIVISION_BY_ZERO),
 				 errmsg("division by zero")));
+		/* ensure compiler realizes we mustn't reach the division (gcc bug) */
+		PG_RETURN_NULL();
+	}
+
 	/* No overflow is possible */
 	PG_RETURN_INT32((int32) arg1 / arg2);
 }

src/backend/utils/adt/int8.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/int8.c,v 1.74 2009/06/11 14:49:03 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/int8.c,v 1.75 2009/09/03 18:48:14 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -919,9 +919,14 @@ int48div(PG_FUNCTION_ARGS)
 	int64		arg2 = PG_GETARG_INT64(1);
 
 	if (arg2 == 0)
+	{
 		ereport(ERROR,
 				(errcode(ERRCODE_DIVISION_BY_ZERO),
 				 errmsg("division by zero")));
+		/* ensure compiler realizes we mustn't reach the division (gcc bug) */
+		PG_RETURN_NULL();
+	}
+
 	/* No overflow is possible */
 	PG_RETURN_INT64((int64) arg1 / arg2);
 }
@@ -1098,9 +1103,14 @@ int28div(PG_FUNCTION_ARGS)
 	int64		arg2 = PG_GETARG_INT64(1);
 
 	if (arg2 == 0)
+	{
 		ereport(ERROR,
 				(errcode(ERRCODE_DIVISION_BY_ZERO),
 				 errmsg("division by zero")));
+		/* ensure compiler realizes we mustn't reach the division (gcc bug) */
+		PG_RETURN_NULL();
+	}
+
 	/* No overflow is possible */
 	PG_RETURN_INT64((int64) arg1 / arg2);
 }