Bug #67043 [Opn->Asn]: substr_compare falsely reports equality on negative offset

Edit report at https://bugs.php.net/bug.php?id=67043&edit=1 ID: 67043 Updated by: aharvey@php.net Reported by: php at kirk dot at Summary: substr_compare falsely reports equality on negative offset -Status: Open +Status: Assigned Type: Bug Package: Strings related Operating System: any PHP Version: 5.5.11 -Assigned To: +Assigned To: datibbaw Block user comment: N Private report: N New Comment: That does appear to be the relevant commit, per a git bisect. Tjerk, can you have a look at this, please? Previous Comments: ------------------------------------------------------------------------ [2014-04-08 09:53:26] php at kirk dot at Saw this bug on multiple OSes, therefore changing OS to any. ------------------------------------------------------------------------ [2014-04-08 09:40:19] php at kirk dot at Description: ------------ Since version 5.5.11 a substr_compare with a negative 3rd parameter (=offset, thus it should start counting from the end of the string) incorrectly reports equality. See http://3v4l.org/8co5P I believe the bug could have been introduced in this commit: https://github.com/datibbaw/php-src/commit/e292391b3899ed2d80a8f44dc94074d68328c6ea What caught my eye is the introduced cast to an unsigned integer but I don't know if this really is the source of the bug. Workaround: specify a length (absolute value of the negative offset) Test script: --------------- var_dump(substr_compare("template", "_emplate", -8)); var_dump(substr_compare("template", "_emplate", -8, 8)); Expected result: ---------------- int(21) int(21) Actual result: -------------- int(0) int(21) ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=67043&edit=1