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Update substr() behavior
1 parent 83d8f68 commit 7417222

6 files changed

Lines changed: 282 additions & 135 deletions

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CHANGELOG.md

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org).
66

77
## [Unreleased]
88

9+
### Fixed
10+
- Fixed `substr()` returning `false` where PHP returns a string. The kernel implementation was a hand-port of PHP 5.6's `substr()` and rejected inputs that PHP clamps: an offset equal to the subject length (`substr("GetPosts", 8)`), an offset past the end, any offset into an empty subject (`substr("", 0)`), and a negative length larger than the subject (`substr("abcdef", 0, -10)`) all returned `false`. Non-string scalars were rejected outright instead of being coerced. The kernel now mirrors PHP 8's clamping, so `substr()` never returns `false`, and `null`, `false` and `true` coerce to `""`, `""` and `"1"` as they do in PHP
11+
912
## [1.2.0] - 2026-07-27
1013

1114
### Added

ext/kernel/string.c

Lines changed: 27 additions & 63 deletions
Original file line numberDiff line numberDiff line change
@@ -286,85 +286,49 @@ void zephir_substr(zval *return_value, zval *str, long f, long l, int flags)
286286
{
287287
zval copy;
288288
int use_copy = 0;
289-
int str_len;
289+
size_t str_len;
290290

291+
/* Matches PHP's scalar coercion: null -> "", false -> "", true -> "1" */
291292
if (Z_TYPE_P(str) != IS_STRING) {
292-
293-
if (Z_TYPE_P(str) == IS_NULL || Z_TYPE_P(str) == IS_TRUE || Z_TYPE_P(str) == IS_FALSE) {
294-
RETURN_FALSE;
295-
}
296-
297-
if (Z_TYPE_P(str) != IS_STRING) {
298-
use_copy = zend_make_printable_zval(str, &copy);
299-
if (use_copy) {
300-
str = ©
301-
}
302-
}
303-
}
304-
305-
str_len = Z_STRLEN_P(str);
306-
if ((flags & ZEPHIR_SUBSTR_NO_LENGTH) == ZEPHIR_SUBSTR_NO_LENGTH) {
307-
l = str_len;
308-
}
309-
310-
if ((l < 0 && -l > str_len)) {
311-
if (use_copy) {
312-
zval_dtor(str);
313-
}
314-
RETURN_FALSE;
315-
} else {
316-
if (l > str_len) {
317-
l = str_len;
318-
}
319-
}
320-
321-
if (f > str_len) {
293+
use_copy = zend_make_printable_zval(str, &copy);
322294
if (use_copy) {
323-
zval_dtor(str);
324-
}
325-
RETURN_FALSE;
326-
} else {
327-
if (f < 0 && -f > str_len) {
328-
f = 0;
295+
str = &copy;
329296
}
330297
}
331298

332-
if (l < 0 && (l + str_len - f) < 0) {
333-
if (use_copy) {
334-
zval_dtor(str);
335-
}
336-
RETURN_FALSE;
337-
}
299+
str_len = Z_STRLEN_P(str);
338300

339-
/* if "from" position is negative, count start position from the end
340-
* of the string
301+
/* Mirrors PHP_FUNCTION(substr) in php-src ext/standard/string.c (PHP >= 8.0):
302+
* out-of-range offsets and lengths are clamped, never rejected. The size_t
303+
* casts are deliberate - they keep the negation well defined at LONG_MIN.
304+
*
305+
* "from" is clamped first; "length" is then resolved against the *clamped*
306+
* "from", which is what makes negative lengths collapse to an empty string
307+
* instead of failing.
341308
*/
342309
if (f < 0) {
343-
f = str_len + f;
344-
if (f < 0) {
310+
if (-(size_t) f > str_len) {
345311
f = 0;
312+
} else {
313+
f = (long) str_len + f;
346314
}
347-
}
348-
349-
/* if "length" position is negative, set it to the length
350-
* needed to stop that many chars from the end of the string
351-
*/
352-
if (l < 0) {
353-
l = (str_len - f) + l;
354-
if (l < 0) {
355-
l = 0;
356-
}
357-
}
358-
359-
if (f >= str_len) {
315+
} else if ((size_t) f > str_len) {
360316
if (use_copy) {
361317
zval_dtor(str);
362318
}
363-
RETURN_FALSE;
319+
RETURN_EMPTY_STRING();
364320
}
365321

366-
if ((f + l) > str_len) {
367-
l = str_len - f;
322+
if ((flags & ZEPHIR_SUBSTR_NO_LENGTH) == ZEPHIR_SUBSTR_NO_LENGTH) {
323+
l = (long) str_len - f;
324+
} else if (l < 0) {
325+
if (-(size_t) l > str_len - (size_t) f) {
326+
l = 0;
327+
} else {
328+
l = (long) str_len - f + l;
329+
}
330+
} else if ((size_t) l > str_len - (size_t) f) {
331+
l = (long) str_len - f;
368332
}
369333

370334
if (!l) {

kernel/string.c

Lines changed: 27 additions & 63 deletions
Original file line numberDiff line numberDiff line change
@@ -286,85 +286,49 @@ void zephir_substr(zval *return_value, zval *str, long f, long l, int flags)
286286
{
287287
zval copy;
288288
int use_copy = 0;
289-
int str_len;
289+
size_t str_len;
290290

291+
/* Matches PHP's scalar coercion: null -> "", false -> "", true -> "1" */
291292
if (Z_TYPE_P(str) != IS_STRING) {
292-
293-
if (Z_TYPE_P(str) == IS_NULL || Z_TYPE_P(str) == IS_TRUE || Z_TYPE_P(str) == IS_FALSE) {
294-
RETURN_FALSE;
295-
}
296-
297-
if (Z_TYPE_P(str) != IS_STRING) {
298-
use_copy = zend_make_printable_zval(str, &copy);
299-
if (use_copy) {
300-
str = &copy;
301-
}
302-
}
303-
}
304-
305-
str_len = Z_STRLEN_P(str);
306-
if ((flags & ZEPHIR_SUBSTR_NO_LENGTH) == ZEPHIR_SUBSTR_NO_LENGTH) {
307-
l = str_len;
308-
}
309-
310-
if ((l < 0 && -l > str_len)) {
311-
if (use_copy) {
312-
zval_dtor(str);
313-
}
314-
RETURN_FALSE;
315-
} else {
316-
if (l > str_len) {
317-
l = str_len;
318-
}
319-
}
320-
321-
if (f > str_len) {
293+
use_copy = zend_make_printable_zval(str, &copy);
322294
if (use_copy) {
323-
zval_dtor(str);
324-
}
325-
RETURN_FALSE;
326-
} else {
327-
if (f < 0 && -f > str_len) {
328-
f = 0;
295+
str = &copy;
329296
}
330297
}
331298

332-
if (l < 0 && (l + str_len - f) < 0) {
333-
if (use_copy) {
334-
zval_dtor(str);
335-
}
336-
RETURN_FALSE;
337-
}
299+
str_len = Z_STRLEN_P(str);
338300

339-
/* if "from" position is negative, count start position from the end
340-
* of the string
301+
/* Mirrors PHP_FUNCTION(substr) in php-src ext/standard/string.c (PHP >= 8.0):
302+
* out-of-range offsets and lengths are clamped, never rejected. The size_t
303+
* casts are deliberate - they keep the negation well defined at LONG_MIN.
304+
*
305+
* "from" is clamped first; "length" is then resolved against the *clamped*
306+
* "from", which is what makes negative lengths collapse to an empty string
307+
* instead of failing.
341308
*/
342309
if (f < 0) {
343-
f = str_len + f;
344-
if (f < 0) {
310+
if (-(size_t) f > str_len) {
345311
f = 0;
312+
} else {
313+
f = (long) str_len + f;
346314
}
347-
}
348-
349-
/* if "length" position is negative, set it to the length
350-
* needed to stop that many chars from the end of the string
351-
*/
352-
if (l < 0) {
353-
l = (str_len - f) + l;
354-
if (l < 0) {
355-
l = 0;
356-
}
357-
}
358-
359-
if (f >= str_len) {
315+
} else if ((size_t) f > str_len) {
360316
if (use_copy) {
361317
zval_dtor(str);
362318
}
363-
RETURN_FALSE;
319+
RETURN_EMPTY_STRING();
364320
}
365321

366-
if ((f + l) > str_len) {
367-
l = str_len - f;
322+
if ((flags & ZEPHIR_SUBSTR_NO_LENGTH) == ZEPHIR_SUBSTR_NO_LENGTH) {
323+
l = (long) str_len - f;
324+
} else if (l < 0) {
325+
if (-(size_t) l > str_len - (size_t) f) {
326+
l = 0;
327+
} else {
328+
l = (long) str_len - f + l;
329+
}
330+
} else if ((size_t) l > str_len - (size_t) f) {
331+
l = (long) str_len - f;
368332
}
369333

370334
if (!l) {
Lines changed: 127 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,127 @@
1+
<?php
2+
3+
declare(strict_types=1);
4+
5+
/**
6+
* This file is part of the Zephir.
7+
*
8+
* (c) Phalcon Team <team@zephir-lang.com>
9+
*
10+
* For the full copyright and license information, please view
11+
* the LICENSE file that was distributed with this source code.
12+
*/
13+
14+
namespace Extension\Optimizers;
15+
16+
use PHPUnit\Framework\TestCase;
17+
use Stub\Optimizers\Substr;
18+
19+
/**
20+
* Exhaustive differential gate for zephir_substr().
21+
*
22+
* The hand-written cases in SubstrTest document intent; this one proves
23+
* totality by comparing every (subject, from, length) combination against
24+
* native substr(). It exists because the kernel spent ten years diverging
25+
* from PHP on ~24% of its input space without a single test noticing.
26+
*
27+
* Not a data-provider test on purpose: 20k PHPUnit cases would dominate the
28+
* suite's runtime and output. One assertion, full divergence list on failure.
29+
*/
30+
final class SubstrParityTest extends TestCase
31+
{
32+
/**
33+
* Subjects PHP accepts and coerces. Arrays and bare objects are excluded:
34+
* PHP 8 raises TypeError for those, while Zephir routes them through
35+
* zend_make_printable_zval. That delta is pre-existing and out of scope.
36+
*/
37+
private const SUBJECTS = [
38+
"''" => '',
39+
"'a'" => 'a',
40+
"'abcdef'" => 'abcdef',
41+
"'GetPosts'" => 'GetPosts',
42+
'binary' => "\x00ab",
43+
'long20' => 'abcdefghijklmnopqrst',
44+
'null' => null,
45+
'true' => true,
46+
'false' => false,
47+
'int0' => 0,
48+
'int12345' => 12345,
49+
'float1.5' => 1.5,
50+
];
51+
52+
public function testMatchesNativeSubstrForEveryCombination(): void
53+
{
54+
$test = new Substr();
55+
$divergent = [];
56+
$combos = 0;
57+
58+
foreach (self::SUBJECTS as $name => $subject) {
59+
// This file declares strict_types, so native substr() would reject a
60+
// non-string subject outright. Cast first: (string) reproduces exactly
61+
// the weak-mode coercion PHP applies to a string parameter
62+
// (null -> "", false -> "", true -> "1", 1.5 -> "1.5"), which is the
63+
// behaviour the kernel is being held to.
64+
$native = (string) $subject;
65+
66+
// Span is driven by the coerced length so the sweep always straddles
67+
// the len-1 / len / len+1 boundary where the off-by-one lived.
68+
$span = strlen($native) + 4;
69+
$froms = array_merge(range(-$span, $span), [PHP_INT_MIN, PHP_INT_MAX]);
70+
$lens = array_merge(range(-$span, $span), [PHP_INT_MIN, PHP_INT_MAX]);
71+
72+
foreach ($froms as $from) {
73+
++$combos;
74+
$this->collect(
75+
$divergent,
76+
$name,
77+
$from,
78+
null,
79+
$test->testTwoArguments($subject, $from),
80+
substr($native, $from)
81+
);
82+
83+
foreach ($lens as $len) {
84+
++$combos;
85+
$this->collect(
86+
$divergent,
87+
$name,
88+
$from,
89+
$len,
90+
$test->testThreeArguments($subject, $from, $len),
91+
substr($native, $from, $len)
92+
);
93+
}
94+
}
95+
}
96+
97+
$this->assertSame(
98+
[],
99+
$divergent,
100+
sprintf(
101+
"zephir_substr() diverges from native substr() in %d of %d combinations:\n%s",
102+
count($divergent),
103+
$combos,
104+
implode("\n", array_slice($divergent, 0, 40))
105+
)
106+
);
107+
}
108+
109+
/**
110+
* @param list<string> $divergent
111+
*/
112+
private function collect(array &$divergent, string $name, int $from, ?int $len, $actual, $expected): void
113+
{
114+
if ($actual === $expected) {
115+
return;
116+
}
117+
118+
$divergent[] = sprintf(
119+
' %s from=%s length=%s -> zephir=%s php=%s',
120+
$name,
121+
$from,
122+
$len ?? '-',
123+
var_export($actual, true),
124+
var_export($expected, true)
125+
);
126+
}
127+
}

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