Fix rounding of zend_dval_to_lval

cataphract · cataphract · commit a86fcfbc1d39 · 2013-02-23T16:55:50.000Z
Now rounding is always towards zero; the rounding can be though as if
occurring on the original double. Only relevant for the 32-bit long
variant.
diff --git a/Zend/tests/dval_to_lval_32.phpt b/Zend/tests/dval_to_lval_32.phpt
@@ -15,6 +15,8 @@ if (PHP_INT_SIZE != 4)
 		-3999999999999999475712.,
 		-3999999999999998951424.,
 	];
+	/* see if we're rounding negative numbers right */
+	$values[] = -2147483649.8;
 
 	foreach ($values as $v) {
 		var_dump((int)$v);
@@ -27,3 +29,4 @@ int(-2055733248)
 int(-2055208960)
 int(-2054684672)
 int(-2054160384)
+int(2147483647)
diff --git a/Zend/zend_operators.h b/Zend/zend_operators.h
@@ -77,7 +77,9 @@ static zend_always_inline long zend_dval_to_lval(double d)
 
 		dmod = fmod(d, two_pow_32);
 		if (dmod < 0) {
-			dmod += two_pow_32;
+			/* we're going to make this number positive; call ceil()
+			 * to simulate rounding towards 0 of the negative number */
+			dmod = ceil(dmod) + two_pow_32;
 		}
 		return (long)(unsigned long)dmod;
 	}
@@ -93,6 +95,8 @@ static zend_always_inline long zend_dval_to_lval(double d)
 
 		dmod = fmod(d, two_pow_64);
 		if (dmod < 0) {
+			/* no need to call ceil; original double must have had no
+			 * fractional part, hence dmod does not have one either */
 			dmod += two_pow_64;
 		}
 		return (long)(unsigned long)dmod;

Original file line number	Diff line number	Diff line change
`@@ -77,7 +77,9 @@ static zend_always_inline long zend_dval_to_lval(double d)`
`77`	`77`
`78`	`78`	`dmod = fmod(d, two_pow_32);`
`79`	`79`	`if (dmod < 0) {`
`80`		`- dmod += two_pow_32;`
	`80`	`+ /* we're going to make this number positive; call ceil()`
	`81`	`+ * to simulate rounding towards 0 of the negative number */`
	`82`	`+ dmod = ceil(dmod) + two_pow_32;`
`81`	`83`	`}`
`82`	`84`	`return (long)(unsigned long)dmod;`
`83`	`85`	`}`
`@@ -93,6 +95,8 @@ static zend_always_inline long zend_dval_to_lval(double d)`
`93`	`95`
`94`	`96`	`dmod = fmod(d, two_pow_64);`
`95`	`97`	`if (dmod < 0) {`
	`98`	`+ /* no need to call ceil; original double must have had no`
	`99`	`+ * fractional part, hence dmod does not have one either */`
`96`	`100`	`dmod += two_pow_64;`
`97`	`101`	`}`
`98`	`102`	`return (long)(unsigned long)dmod;`