Edit report at https://bugs.php.net/bug.php?id=73913&edit=1
ID: 73913
Comment by: dima at virtuman dot com
Reported by: proartex at mail dot ru
Summary: broken strrpos with negative offset
Status: Assigned
Type: Bug
Package: Strings related
Operating System: macOS Sierra 10.12.1
PHP Version: 5.6.29
Assigned To: heiglandreas
Block user comment: N
Private report: N
New Comment:
Looks like the problem is related to https://github.com/php/php-src/blob/PHP-5.6.29/ext/standard/string.c#L1987
replace this one:
e = haystack + haystack_len + offset;
with this one:
e = haystack + haystack_len + offset - needle_len;
will solve the problem.
Previous Comments:
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[2017-01-11 21:57:27] heiglandreas@php.net
Looks like you're right! I dug deeper into it and it seems there is an issue when the negative
offset is smaller or equals the size of the needle.
I'm digging deeper into it.
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[2017-01-11 18:03:34] proartex at mail dot ru
1. Does strrpos("works_like_a_charm", 'charm', 15) really equals to
strrpos("works_like_a_charm", 'charm', -3)? false != 13. It is also applicable
for 3 last cases.
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[2017-01-11 17:32:03] heiglandreas@php.net
when offset is negative the search *starts* that many characters *from the end*. The search is not
excluding the last n characters.
strrpos("aaaa", 'aa', -2) == strrpos("aaaa", 'aa', 2)
strrpos("aaaa", 'a', -1) == strrpos("aaaa", 'a', 3)
strrpos("/documents/show/5474", '/', -20) ==
strrpos("/documents/show/5474", '/', 0)
strrpos("works_like_a_charm", 'charm', -3) ==
strrpos("works_like_a_charm", 'charm', 15)
strrpos("works_like_a_charm", 'charm', -4) ==
strrpos("works_like_a_charm", 'charm', 14)
So they work as expected.
What you want to do would be achieved by this:
strrpos(substr("aaaa", -2), "aa");
When needle is longer than the remaining string, the offset seems to be expanded to at least include
the needle.
Note also the comment on http://php.net/manual/de/function.strrpos.php#76447
------------------------------------------------------------------------
[2017-01-11 17:19:23] proartex at mail dot ru
last case must be var_dump(strrpos("works_like_a_charm", 'charm', -5)); //ER:
false, AR: 13
------------------------------------------------------------------------
[2017-01-11 17:16:36] proartex at mail dot ru
Description:
------------
It is seems broken at least in the following cases:
- if negative offset equals to haystack length;
- if negative offset less than needle length;
- if needle length equals to (haystack length + negative offset)
Negative offset should not move pointer but reduce search scope on the value of offset. In that case
character placed at 0 position must not be found if search scope is reduced to empty string. Same
should be applied in boundary cases: character placed next to reduced search scope must not be found
(last case).
Test script:
---------------
<?php
var_dump(strrpos("aaaa", 'aa', -2)); //ER: 0, AR: 2
var_dump(strrpos("aaaa", 'a', -1)); //ER: 2, AR: 3
var_dump(strrpos("/documents/show/5474", '/', -20)); //ER: false, AR: 0
var_dump(strrpos("works_like_a_charm", 'charm', -3)); //ER: false, AR: 13
var_dump(strrpos("works_like_a_charm", 'charm', -4)); //ER: false, AR: 13
Expected result:
----------------
0
2
false
false
false
Actual result:
--------------
2
3
0
13
13
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Edit this bug report at https://bugs.php.net/bug.php?id=73913&edit=1