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Commit64f5edc

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pgbench: Install guards against obscure overflow conditions.
Dividing INT_MIN by -1 or taking INT_MIN modulo -1 can sometimescause floating-point exceptions or otherwise misbehave.Fabien Coelho and Michael Paquier
1 parent89611c4 commit64f5edc

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1 file changed

+34
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‎src/bin/pgbench/pgbench.c

Lines changed: 34 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1047,7 +1047,29 @@ evaluateExpr(CState *st, PgBenchExpr *expr, int64 *retval)
10471047
fprintf(stderr,"division by zero\n");
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return false;
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}
1050-
*retval=lval /rval;
1050+
1051+
/*
1052+
* INT64_MIN / -1 is problematic, since the result
1053+
* can't be represented on a two's-complement machine.
1054+
* Some machines produce INT64_MIN, some produce zero,
1055+
* some throw an exception. We can dodge the problem
1056+
* by recognizing that division by -1 is the same as
1057+
* negation.
1058+
*/
1059+
if (rval==-1)
1060+
{
1061+
*retval=-lval;
1062+
1063+
/* overflow check (needed for INT64_MIN) */
1064+
if (lval==PG_INT64_MIN)
1065+
{
1066+
fprintf(stderr,"bigint out of range\n");
1067+
return false;
1068+
}
1069+
}
1070+
else
1071+
*retval=lval /rval;
1072+
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return true;
10521074

10531075
case'%':
@@ -1056,7 +1078,17 @@ evaluateExpr(CState *st, PgBenchExpr *expr, int64 *retval)
10561078
fprintf(stderr,"division by zero\n");
10571079
return false;
10581080
}
1059-
*retval=lval %rval;
1081+
1082+
/*
1083+
* Some machines throw a floating-point exception for
1084+
* INT64_MIN % -1. Dodge that problem by noting that
1085+
* any value modulo -1 is 0.
1086+
*/
1087+
if (rval==-1)
1088+
*retval=0;
1089+
else
1090+
*retval=lval %rval;
1091+
10601092
return true;
10611093
}
10621094

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