[php-src] Issue #19088: sscanf c conversion specifier
| From: | hakre | Date: | Thu, 10 Jul 2025 20:51:12 +0000 |
| Subject: | [php-src] Issue #19088: sscanf c conversion specifier | ||
| Groups: | php.bugs | ||
| Request: | Send a blank email to php-bugs+get-250413@lists.php.net to get a copy of this message | ||
Issue: https://github.com/php/php-src/issues/19088
Author: hakre
### Description
The following code:
```php
<?php
$r = sscanf(' ', '%c%n', $c, $n)
and var_dump(compact('r', 'c', 'n'));
```
Resulted in this output:
```
array(3) {
'r' =>
int(2)
'c' =>
string(0) ""
'n' =>
int(0)
}
```
But I expected this output instead:
```
array(3) {
'r' =>
int(2)
'c' =>
string(1) " "
'n' =>
int(1)
}
```
---
Expectation by _fscanf, scanf, sscanf - convert formatted input_, cf. Revision of IEEE Std
1003.1-2008, via [Open Group Base Specifications Issue 7, 2018
edition](https://pubs.opengroup.org/onlinepubs/9699919799/functions/scanf.html), specifically
_"\[CX] The functionality described on this reference page is aligned with the ISO C standard.
Any conflict between the requirements described here and the ISO C standard is unintentional. This
volume of POSIX.1-2017 defers to the ISO C standard"_, quoting:
> The following conversion specifiers are valid:
>
> [...]
>
> * c
> * Matches a sequence of bytes of the number specified by the field width (1 if no field
> width is present in the conversion specification). No null byte is added. The normal skip over
> white-space characters shall be suppressed in this case.
For PHP versions older of that date, please refer to the equally older documentation for these
dates.
Why is the expectation important?
The _c_ conversion specifier is important to scan over white space characters, so that it adjoins
the _s_ conversion specifier (supported by PHP sscanf(), compare https://github.com/php/php-src/issues/11201#issuecomment-1537369396
) and/or leaving a space character in the $format string (supported by PHP sscanf()).
---
https://3v4l.org/9E2d1
8.4.10
```3v4l.org
https://3v4l.org/9E2d1 9E2d1
1: <?php
2:
3: $r = sscanf(' ', '%c%n', $c, $n)
4: and var_dump(compact('r', 'c', 'n'));
5:
output [versions: 8.4.10 | released 2025-07-03 | took 29 ms, 18.55 MiB]
O: array(3) {
O: ["r"]=>
O: int(2)
O: ["c"]=>
O: string(0) ""
O: ["n"]=>
O: int(0)
O: }
```
+eol:
```3v4l.org
https://3v4l.org/9E2d1 9E2d1
1: <?php
2:
3: $r = sscanf(' ', '%c%n', $c, $n)
4: and var_dump(compact('r', 'c', 'n'));
5:
output [versions: 4.3.2 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0
- 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.4 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 -
7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 -
8.3.23, 8.4.1 - 8.4.10]
O: array(3) {
O: ["r"]=>
O: int(2)
O: ["c"]=>
O: string(0) ""
O: ["n"]=>
O: int(0)
O: }
output [versions: 7.0.0 - 7.0.3]
O: array(3) {
O: ["r"]=>
O: int(2)
O: ["c"]=>
O: &string(0) ""
O: ["n"]=>
O: &int(0)
O: }
output [versions: 4.3.0 - 4.3.1]
O: array(3) {
O: ["r"]=>
O: int(2)
O: ["c"]=>
O: string(0) ""
O: ["n"]=>
O: string(0) ""
O: }
```
### PHP Version
```plain
PHP 8.4.10 (cli) (built: Jul 3 2025 12:41:53) (NTS)
Copyright (c) The PHP Group
Built by Debian
Zend Engine v4.4.10, Copyright (c) Zend Technologies
with Zend OPcache v8.4.10, Copyright (c), by Zend Technologies
with Xdebug v3.4.4, Copyright (c) 2002-2025, by Derick Rethans
```
### Operating System
_No response_