On further reflection, we'd better do the same in int.c.

We previously heard of the same problem in int24div(), so there's not a
good reason to suppose the problem is confined to cases involving int8.

diff --git a/src/backend/utils/adt/int.c b/src/backend/utils/adt/int.c
index ab8476b..609c3a7 100644 (file)
--- a/src/backend/utils/adt/int.c
+++ b/src/backend/utils/adt/int.c
@@ -723,9 +723,13 @@ int4div(PG_FUNCTION_ARGS)
        int32           result;
 
        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();
+       }
 
 #ifdef WIN32
 
@@ -864,9 +868,13 @@ int2div(PG_FUNCTION_ARGS)
        int16           result;
 
        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();
+       }
 
        result = arg1 / arg2;
 
@@ -1048,9 +1056,13 @@ int42div(PG_FUNCTION_ARGS)
        int32           result;
 
        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();
+       }
 
        result = arg1 / arg2;
 
@@ -1074,9 +1086,13 @@ int4mod(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();
+       }
 
        /* SELECT ((-2147483648)::int4) % (-1); causes a floating point exception */
        if (arg1 == INT_MIN && arg2 == -1)
@@ -1094,9 +1110,14 @@ int2mod(PG_FUNCTION_ARGS)
        int16           arg2 = PG_GETARG_INT16(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_INT16(arg1 % arg2);