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standard: Handle negative zero in min()/max() #20223

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ae9fd51
standard: Handle negative zero in `min()`/`max()`
TimWolla Oct 19, 2025
0c4ae12
standard: Handle `min()`/`max()` for `float(-0.0)` and `int(0)`
TimWolla Oct 19, 2025
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32 changes: 23 additions & 9 deletions ext/standard/array.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1170,7 +1170,15 @@ PHP_FUNCTION(key)

static int php_data_compare(const void *f, const void *s) /* {{{ */
{
return zend_compare((zval*)f, (zval*)s);
zval *zf = (zval*)f;
zval *zs = (zval*)s;

int result = zend_compare(zf, zs);
if (UNEXPECTED(result == 0 && Z_TYPE_P(zf) == IS_DOUBLE && Z_TYPE_P(zs) == IS_DOUBLE)) {
return signbit(Z_DVAL_P(zs)) - signbit(Z_DVAL_P(zf));
}

return result;
}
/* }}} */

Expand Down Expand Up @@ -1235,7 +1243,7 @@ PHP_FUNCTION(min)
for (i = 1; i < argc; i++) {
if (EXPECTED(Z_TYPE(args[i]) == IS_DOUBLE)) {
double_compare:
if (min_dval > Z_DVAL(args[i])) {
if (min_dval > Z_DVAL(args[i]) || UNEXPECTED(signbit(Z_DVAL(args[i])) > signbit(min_dval))) {
min_dval = Z_DVAL(args[i]);
min = &args[i];
}
Expand Down Expand Up @@ -1270,7 +1278,7 @@ ZEND_FRAMELESS_FUNCTION(min, 2)
Z_FLF_PARAM_ZVAL(1, lhs);
Z_FLF_PARAM_ZVAL(2, rhs);

double lhs_dval;
double lhs_dval, rhs_dval;

if (Z_TYPE_P(lhs) == IS_LONG) {
zend_long lhs_lval = Z_LVAL_P(lhs);
Expand All @@ -1289,10 +1297,13 @@ ZEND_FRAMELESS_FUNCTION(min, 2)

if (EXPECTED(Z_TYPE_P(rhs) == IS_DOUBLE)) {
double_compare:
RETURN_COPY_VALUE(lhs_dval < Z_DVAL_P(rhs) ? lhs : rhs);
rhs_dval = Z_DVAL_P(rhs);
double_compare2:
RETURN_COPY_VALUE(lhs_dval < rhs_dval || UNEXPECTED(signbit(lhs_dval) > signbit(rhs_dval)) ? lhs : rhs);
} else if (Z_TYPE_P(rhs) == IS_LONG && (zend_dval_to_lval_silent((double) Z_LVAL_P(rhs)) == Z_LVAL_P(rhs))) {
/* if the value can be exactly represented as a double, use double dedicated code otherwise generic */
RETURN_COPY_VALUE(lhs_dval < (double)Z_LVAL_P(rhs) ? lhs : rhs);
rhs_dval = (double)Z_LVAL_P(rhs);
goto double_compare2;
} else {
goto generic_compare;
}
Expand Down Expand Up @@ -1363,7 +1374,7 @@ PHP_FUNCTION(max)
for (i = 1; i < argc; i++) {
if (EXPECTED(Z_TYPE(args[i]) == IS_DOUBLE)) {
double_compare:
if (max_dval < Z_DVAL(args[i])) {
if (max_dval < Z_DVAL(args[i]) || UNEXPECTED(signbit(Z_DVAL(args[i])) < signbit(max_dval))) {
max_dval = Z_DVAL(args[i]);
max = &args[i];
}
Expand Down Expand Up @@ -1398,7 +1409,7 @@ ZEND_FRAMELESS_FUNCTION(max, 2)
Z_FLF_PARAM_ZVAL(1, lhs);
Z_FLF_PARAM_ZVAL(2, rhs);

double lhs_dval;
double lhs_dval, rhs_dval;

if (Z_TYPE_P(lhs) == IS_LONG) {
zend_long lhs_lval = Z_LVAL_P(lhs);
Expand All @@ -1417,10 +1428,13 @@ ZEND_FRAMELESS_FUNCTION(max, 2)

if (EXPECTED(Z_TYPE_P(rhs) == IS_DOUBLE)) {
double_compare:
RETURN_COPY_VALUE(lhs_dval >= Z_DVAL_P(rhs) ? lhs : rhs);
rhs_dval = Z_DVAL_P(rhs);
double_compare2:
RETURN_COPY_VALUE(lhs_dval > rhs_dval || UNEXPECTED(signbit(lhs_dval) < signbit(rhs_dval)) ? lhs : rhs);
} else if (Z_TYPE_P(rhs) == IS_LONG && (zend_dval_to_lval_silent((double) Z_LVAL_P(rhs)) == Z_LVAL_P(rhs))) {
/* if the value can be exactly represented as a double, use double dedicated code otherwise generic */
RETURN_COPY_VALUE(lhs_dval >= (double)Z_LVAL_P(rhs) ? lhs : rhs);
rhs_dval = (double)Z_LVAL_P(rhs);
goto double_compare2;
} else {
goto generic_compare;
}
Expand Down
90 changes: 90 additions & 0 deletions ext/standard/tests/math/gh20221.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,90 @@
--TEST--
GH-20221: max/min return wrong value if signed (negative) zero
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does also apply for sort - https://3v4l.org/9UMvV

--FILE--
<?php

foreach ([-0.0, 0.0] as $a) {
foreach ([-0.0, 0.0] as $b) {
if ("$a $b" === "0 0" || "$a $b" === "-0 -0") {
continue;
}

printf("min(%.17g, %.17g) = %.17g\n", $a, $b, min($a, $b));
printf("min([%.17g, %.17g]) = %.17g\n", $a, $b, min([$a, $b]));
printf("max(%.17g, %.17g) = %.17g\n", $a, $b, max($a, $b));
printf("max([%.17g, %.17g]) = %.17g\n", $a, $b, max([$a, $b]));
echo "\n";
}
}

echo "======\n\n";

foreach ([-0.0, 0.0] as $a) {
foreach ([-0.0, 0.0] as $b) {
foreach ([-0.0, 0.0] as $c) {
if ("$a $b $c" === "0 0 0" || "$a $b $c" === "-0 -0 -0") {
continue;
}

printf("min(%.17g, %.17g, %.17g) = %.17g\n", $a, $b, $c, min($a, $b, $c));
printf("min([%.17g, %.17g, %.17g]) = %.17g\n", $a, $b, $c, min([$a, $b, $c]));
printf("max(%.17g, %.17g, %.17g) = %.17g\n", $a, $b, $c, max($a, $b, $c));
printf("max([%.17g, %.17g, %.17g]) = %.17g\n", $a, $b, $c, max([$a, $b, $c]));
echo "\n";
}
}
}

var_dump(min( 0, -0.0 ));
var_dump(min( -0.0, 0 ));
var_dump(max( 0, -0.0 ));
var_dump(max( -0.0, 0 ));

?>
--EXPECT--
min(-0, 0) = -0
min([-0, 0]) = -0
max(-0, 0) = 0
max([-0, 0]) = 0

min(0, -0) = -0
min([0, -0]) = -0
max(0, -0) = 0
max([0, -0]) = 0

======

min(-0, -0, 0) = -0
min([-0, -0, 0]) = -0
max(-0, -0, 0) = 0
max([-0, -0, 0]) = 0

min(-0, 0, -0) = -0
min([-0, 0, -0]) = -0
max(-0, 0, -0) = 0
max([-0, 0, -0]) = 0

min(-0, 0, 0) = -0
min([-0, 0, 0]) = -0
max(-0, 0, 0) = 0
max([-0, 0, 0]) = 0

min(0, -0, -0) = -0
min([0, -0, -0]) = -0
max(0, -0, -0) = 0
max([0, -0, -0]) = 0

min(0, -0, 0) = -0
min([0, -0, 0]) = -0
max(0, -0, 0) = 0
max([0, -0, 0]) = 0

min(0, 0, -0) = -0
min([0, 0, -0]) = -0
max(0, 0, -0) = 0
max([0, 0, -0]) = 0

float(-0)
float(-0)
int(0)
int(0)
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