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Fixed GH-18266: round() - Added edge case generation logic #18936

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Fixed GH-18266: round() - Added edge case generation logic #18936

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18 changes: 15 additions & 3 deletions ext/standard/math.c
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Original file line number Diff line number Diff line change
Expand Up @@ -51,9 +51,21 @@ static inline double php_intpow10(int power) {

static zend_always_inline double php_round_get_basic_edge_case(double integral, double exponent, int places)
{
return (places > 0)
? fabs((integral + copysign(0.5, integral)) / exponent)
: fabs((integral + copysign(0.5, integral)) * exponent);
/* Integer + `0.5` can be represented exactly in a double, so in most cases, there is no rounding error at this point. */
double edge_case = integral + copysign(0.5, integral);

/* When the calculation precision is as high as `1e16`, adding `0.5` may be lost due to rounding.
* In such cases, the exponent is applied individually before performing the addition.
* This approach is not used all the time in order to avoid introducing rounding errors when adding `0.5`.
* It is only used when the precision is so fine that adding `0.5` would have no meaningful effect. */
if (UNEXPECTED(integral == edge_case)) {
return (places > 0)
? fabs((integral / exponent) + (copysign(0.5, integral) / exponent))
: fabs((integral * exponent) + (copysign(0.5, integral) * exponent));
}

/* Returns a value adjusted with the exponent so that it can be compared with the input. */
return (places > 0) ? fabs(edge_case / exponent) : fabs(edge_case * exponent);
}

static zend_always_inline double php_round_get_zero_edge_case(double integral, double exponent, int places)
Expand Down
48 changes: 48 additions & 0 deletions ext/standard/tests/math/round_gh12143_expand_rounding_target.phpt
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,9 @@ $testCases = [
[-12345678901234565, -1],
[4503599627370495.5, 0],
[-4503599627370495.5, 0],
[5.0, 15],
[5000000000000000.0, 0],
[5000000000000000.5, 0],
],
'PHP_ROUND_HALF_DOWN' => [
[0.12345678901234565, 16],
Expand All @@ -21,6 +24,9 @@ $testCases = [
[-12345678901234565, -1],
[4503599627370495.5, 0],
[-4503599627370495.5, 0],
[5.0, 15],
[5000000000000000.0, 0],
[5000000000000000.5, 0],
],
'PHP_ROUND_HALF_EVEN' => [
[0.12345678901234565, 16],
Expand All @@ -29,6 +35,9 @@ $testCases = [
[-12345678901234565, -1],
[4503599627370495.5, 0],
[-4503599627370495.5, 0],
[5.0, 15],
[5000000000000000.0, 0],
[5000000000000000.5, 0],
],
'PHP_ROUND_HALF_ODD' => [
[0.12345678901234565, 16],
Expand All @@ -37,6 +46,9 @@ $testCases = [
[-12345678901234565, -1],
[4503599627370495.5, 0],
[-4503599627370495.5, 0],
[5.0, 15],
[5000000000000000.0, 0],
[5000000000000000.5, 0],
],
'RoundingMode::AwayFromZero' => [
[0.12345678901234560, 16],
Expand All @@ -45,6 +57,9 @@ $testCases = [
[-12345678901234567, -1],
[4503599627370495.5, 0],
[-4503599627370495.5, 0],
[5.0, 15],
[5000000000000000.0, 0],
[5000000000000000.5, 0],
],
'RoundingMode::TowardsZero' => [
[0.12345678901234566, 16],
Expand All @@ -53,6 +68,9 @@ $testCases = [
[-12345678901234565, -1],
[4503599627370495.5, 0],
[-4503599627370495.5, 0],
[5.0, 15],
[5000000000000000.0, 0],
[5000000000000000.5, 0],
],
'RoundingMode::PositiveInfinity' => [
[0.12345678901234560, 16],
Expand All @@ -61,6 +79,9 @@ $testCases = [
[-12345678901234564, -1],
[4503599627370495.5, 0],
[-4503599627370495.5, 0],
[5.0, 15],
[5000000000000000.0, 0],
[5000000000000000.5, 0],
],
'RoundingMode::NegativeInfinity' => [
[0.12345678901234560, 16],
Expand All @@ -69,6 +90,9 @@ $testCases = [
[-12345678901234564, -1],
[4503599627370495.5, 0],
[-4503599627370495.5, 0],
[5.0, 15],
[5000000000000000.0, 0],
[5000000000000000.5, 0],
],
];

Expand All @@ -88,6 +112,9 @@ float(12345678901234570)
float(-12345678901234570)
float(4503599627370496)
float(-4503599627370496)
float(5)
float(5000000000000001)
float(5000000000000001)

========== PHP_ROUND_HALF_DOWN ==========
float(0.1234567890123456)
Expand All @@ -96,6 +123,9 @@ float(12345678901234560)
float(-12345678901234560)
float(4503599627370495)
float(-4503599627370495)
float(5)
float(5000000000000000)
float(5000000000000000)

========== PHP_ROUND_HALF_EVEN ==========
float(0.1234567890123456)
Expand All @@ -104,6 +134,9 @@ float(12345678901234560)
float(-12345678901234560)
float(4503599627370496)
float(-4503599627370496)
float(5)
float(5000000000000000)
float(5000000000000000)

========== PHP_ROUND_HALF_ODD ==========
float(0.1234567890123457)
Expand All @@ -112,6 +145,9 @@ float(12345678901234570)
float(-12345678901234570)
float(4503599627370495)
float(-4503599627370495)
float(5)
float(5000000000000001)
float(5000000000000001)

========== RoundingMode::AwayFromZero ==========
float(0.1234567890123456)
Expand All @@ -120,6 +156,9 @@ float(12345678901234570)
float(-12345678901234570)
float(4503599627370496)
float(-4503599627370496)
float(5)
float(5000000000000000)
float(5000000000000000)

========== RoundingMode::TowardsZero ==========
float(0.1234567890123456)
Expand All @@ -128,6 +167,9 @@ float(12345678901234560)
float(-12345678901234560)
float(4503599627370495)
float(-4503599627370495)
float(5)
float(5000000000000000)
float(5000000000000000)

========== RoundingMode::PositiveInfinity ==========
float(0.1234567890123456)
Expand All @@ -136,6 +178,9 @@ float(12345678901234570)
float(-12345678901234560)
float(4503599627370496)
float(-4503599627370495)
float(5)
float(5000000000000000)
float(5000000000000000)

========== RoundingMode::NegativeInfinity ==========
float(0.1234567890123456)
Expand All @@ -144,3 +189,6 @@ float(12345678901234560)
float(-12345678901234570)
float(4503599627370495)
float(-4503599627370496)
float(5)
float(5000000000000000)
float(5000000000000000)