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Commit829757c

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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 parent40482e6 commit829757c

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+34
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‎src/bin/pgbench/pgbench.c

Lines changed: 34 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -961,7 +961,29 @@ evaluateExpr(CState *st, PgBenchExpr *expr, int64 *retval)
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fprintf(stderr,"division by zero\n");
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return false;
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}
964-
*retval=lval /rval;
964+
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/*
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* INT64_MIN / -1 is problematic, since the result
967+
* can't be represented on a two's-complement machine.
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* Some machines produce INT64_MIN, some produce zero,
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* some throw an exception. We can dodge the problem
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* by recognizing that division by -1 is the same as
971+
* negation.
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*/
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if (rval==-1)
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{
975+
*retval=-lval;
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977+
/* overflow check (needed for INT64_MIN) */
978+
if (lval==PG_INT64_MIN)
979+
{
980+
fprintf(stderr,"bigint out of range\n");
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return false;
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}
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}
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else
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*retval=lval /rval;
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return true;
966988

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case'%':
@@ -970,7 +992,17 @@ evaluateExpr(CState *st, PgBenchExpr *expr, int64 *retval)
970992
fprintf(stderr,"division by zero\n");
971993
return false;
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}
973-
*retval=lval %rval;
995+
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/*
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* Some machines throw a floating-point exception for
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* INT64_MIN % -1. Dodge that problem by noting that
999+
* any value modulo -1 is 0.
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*/
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if (rval==-1)
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*retval=0;
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else
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*retval=lval %rval;
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return true;
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}
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