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Fixed GH-12237: sprintf/printf no longer produces negative zero #21273

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Fixed GH-12237: sprintf/printf no longer produces negative zero #21273

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39bf8af
Fixed GH-12237: sprintf/printf no longer produces negative zero
lacatoire Feb 21, 2026
ebc9821
Update formatted_print.c
lacatoire Feb 22, 2026
85ffb7a
Restore rounded variable declaration removed by mistake
lacatoire Feb 23, 2026
ae65bd5
Update vprintf_variation5 test expectation for negative zero fix
lacatoire Feb 23, 2026
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13 changes: 13 additions & 0 deletions ext/standard/formatted_print.c
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Original file line number Diff line number Diff line change
Expand Up @@ -266,6 +266,19 @@ php_sprintf_appenddouble(zend_string **buffer, size_t *pos,
s = php_conv_fp((fmt == 'f')?'F':fmt, number, 0, precision,
(fmt == 'f')?LCONV_DECIMAL_POINT:'.',
&is_negative, &num_buf[1], &s_len);
/* Prevent negative sign when value rounds to zero (GH-12237) */
if (is_negative) {
double rounded;
if (fmt == 'f' || fmt == 'F') {
double factor = pow(10.0, (double)precision);
rounded = round(fabs(number) * factor) / factor;
} else {
rounded = fabs(number);
}
if (rounded == 0.0) {
is_negative = false;
}
}
if (is_negative) {
num_buf[0] = '-';
s = num_buf;
Expand Down
107 changes: 107 additions & 0 deletions ext/standard/tests/strings/gh12237.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,107 @@
--TEST--
GH-12237 (printf/sprintf should not produce negative zero)
--FILE--
<?php

// Basic case from the bug report
echo "-- Basic case --\n";
var_dump(sprintf('%.2f', -0.001));
var_dump(sprintf('%.2f', -0.0));

// Various precisions where the value rounds to zero
echo "-- Precisions rounding to zero --\n";
var_dump(sprintf('%.0f', -0.1));
var_dump(sprintf('%.0f', -0.0));
var_dump(sprintf('%.1f', -0.04));
var_dump(sprintf('%.1f', -0.001));
var_dump(sprintf('%.2f', -0.004));
var_dump(sprintf('%.2f', -0.001));
var_dump(sprintf('%.3f', -0.0004));
var_dump(sprintf('%.3f', -0.0001));
var_dump(sprintf('%.4f', -0.00004));
var_dump(sprintf('%.4f', -0.00001));

// Values that should remain negative (do NOT round to zero)
echo "-- Should stay negative --\n";
var_dump(sprintf('%.2f', -0.01));
var_dump(sprintf('%.2f', -0.1));
var_dump(sprintf('%.2f', -1.5));
var_dump(sprintf('%.1f', -0.1));
var_dump(sprintf('%.0f', -1.0));

// Uppercase F format
echo "-- Uppercase F --\n";
var_dump(sprintf('%.2F', -0.001));
var_dump(sprintf('%.2F', -0.01));

// Explicit positive sign should show + when value rounds to zero
echo "-- Explicit sign --\n";
var_dump(sprintf('%+.2f', -0.001));
var_dump(sprintf('%+.2f', 0.001));
var_dump(sprintf('%+.2f', -0.01));

// printf output (not just sprintf)
echo "-- printf --\n";
printf('%.2f', -0.001);
echo "\n";
printf('%.2f', -0.01);
echo "\n";

// Consistency with number_format
echo "-- number_format consistency --\n";
var_dump(number_format(-0.001, 2));
var_dump(number_format(-0.01, 2));

// Very small negative values that round to zero
echo "-- Very small negatives --\n";
var_dump(sprintf('%.2f', -1e-10));
var_dump(sprintf('%.2f', -PHP_FLOAT_EPSILON));
var_dump(sprintf('%.2f', -1e-100));

// Padding and width
echo "-- Padding --\n";
var_dump(sprintf('%08.2f', -0.001));
var_dump(sprintf('%08.2f', -0.01));

?>
--EXPECT--
-- Basic case --
string(4) "0.00"
string(4) "0.00"
-- Precisions rounding to zero --
string(1) "0"
string(1) "0"
string(3) "0.0"
string(3) "0.0"
string(4) "0.00"
string(4) "0.00"
string(5) "0.000"
string(5) "0.000"
string(6) "0.0000"
string(6) "0.0000"
-- Should stay negative --
string(5) "-0.01"
string(5) "-0.10"
string(5) "-1.50"
string(4) "-0.1"
string(2) "-1"
-- Uppercase F --
string(4) "0.00"
string(5) "-0.01"
-- Explicit sign --
string(5) "+0.00"
string(5) "+0.00"
string(5) "-0.01"
-- printf --
0.00
-0.01
-- number_format consistency --
string(4) "0.00"
string(5) "-0.01"
-- Very small negatives --
string(4) "0.00"
string(4) "0.00"
string(4) "0.00"
-- Padding --
string(8) "00000.00"
string(8) "-0000.01"
36 changes: 18 additions & 18 deletions ext/standard/tests/strings/sprintf_variation9.phpt
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Expand Up @@ -336,15 +336,15 @@ string(8) "0.000000"
string(30) " 0.000000"

-- Iteration 26 --
string(9) "-0.000000"
string(9) "-0.000000"
string(10) " -0.000000"
string(10) "-0.000000 "
string(10) " -0.000000"
string(10) "
-0.000000"
string(9) "-0.000000"
string(30) " -0.000000"
string(8) "0.000000"
string(8) "0.000000"
string(9) " 0.000000"
string(9) "0.000000 "
string(9) " 0.000000"
string(9) "
0.000000"
string(8) "0.000000"
string(30) " 0.000000"

-- Iteration 27 --
string(50) "5000000000000000069686058479707049565356032.000000"
Expand Down Expand Up @@ -380,13 +380,13 @@ string(8) "0.000000"
string(30) " 0.000000"

-- Iteration 30 --
string(9) "-0.000000"
string(9) "-0.000000"
string(10) " -0.000000"
string(10) "-0.000000 "
string(10) " -0.000000"
string(10) "
-0.000000"
string(9) "-0.000000"
string(30) " -0.000000"
string(8) "0.000000"
string(8) "0.000000"
string(9) " 0.000000"
string(9) "0.000000 "
string(9) " 0.000000"
string(9) "
0.000000"
string(8) "0.000000"
string(30) " 0.000000"
Done
4 changes: 2 additions & 2 deletions ext/standard/tests/strings/vprintf_variation5.phpt
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Expand Up @@ -64,8 +64,8 @@ int(28)
int(54)

-- Iteration 4 --
200000.0000 0.0000 -200000.000000 -0.0000
int(45)
200000.0000 0.0000 -200000.000000 0.0000
int(44)

-- Iteration 5 --
20000.000000 -1999999999999999879418332743206357172224.000000 0.000000 20000000000000000000.000000
Expand Down
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