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pgbench: Install guards against obscure overflow conditions.
Dividing INT_MIN by -1 or taking INT_MIN modulo -1 can sometimes cause floating-point exceptions or otherwise misbehave. Fabien Coelho and Michael Paquier
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@ -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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}
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*retval = lval / rval;
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/*
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* INT64_MIN / -1 is problematic, since the result
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* 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
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* negation.
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*/
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if (rval == -1)
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{
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*retval = -lval;
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/* overflow check (needed for INT64_MIN) */
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if (lval == PG_INT64_MIN)
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{
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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;
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case '%':
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@ -970,7 +992,17 @@ 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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}
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*retval = lval % rval;
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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
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* 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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