Bug #69906 [Com]: chr() behavior difference between 32- and 64-bit bulids

Edit report at https://bugs.php.net/bug.php?id=69906&edit=1 ID: 69906 Comment by: jan dot slabon at setasign dot com Reported by: ab@php.net Summary: chr() behavior difference between 32- and 64-bit bulids Status: Not a bug Type: Bug Package: *General Issues Operating System: any PHP Version: 7.0.0alpha1 Assigned To: ab Block user comment: N Private report: N New Comment: Hi Bob, hi Anatol, I reported that problem while talking to Anatol about another bug by email. We really had such code which got broken by this change. So technically it is a BC break but I'm not sure if we are the only one trapping into that issue? We encountered the problem in an Ascii85 encoder which we fixed now by casting to int explicity. So I don't have a problem with this BC break as we've a fix for it: $r = 0; for ($j = 0; $j < 5; ++$j) { $r = (int)($r * 85 + $chn[$j]); } $out .= chr($r >> 24) . chr($r >> 16) . chr($r >> 8) . chr($r); Anyhow this problem will only arise in special situations and will not be recognized until it happens (in our case PDF documents that uses an Ascii85 filter - very rare), which may lead people to think that the code is fine with PHP 7 while it is not... Here are some os projects/packages which current versions are affected: https://packagist.org/search/?q=fpdi https://packagist.org/search/?q=mpdf https://packagist.org/search/?q=pdfparser (depends on https://packagist.org/search/?q=tcpdf which seems to use such structure in its filter class/method, too - which is actually only used by the pdfparser) Additionally there are some hundreds packages depending on these packages, too. If you want to stay with this BC break this have to be documentated. At our end this would force people to update not only to PHP 7 but to the latest library version. So I'm fine with this BC break. Anyhow it could end in some trouble around these packages and users. Cheers, Jan Previous Comments: ------------------------------------------------------------------------ [2015-06-23 21:30:01] ab@php.net Hi Bob, yeah, i was investigating on this but didn't come to update the ticket. You're right, while it's an issue :) I first thought it's an issue on 64-bit, now it looks the issue is on 32-bit (expected should deliver int(173)). Namely - on 32-bit the argument that overflows PHP_INT_MAX will be just truncated to zero (read as 'l' by ZPP or alike). While I saw that there could be a way to fix this on 32-bit, it would be too expensive to be justified. Thus, probably best is to leave it as is, a cast to int should do more or less correct job on this. So kinda marking this as no bug. Thanks. ------------------------------------------------------------------------ [2015-06-23 20:15:04] bwoebi@php.net May I request to not have that changed? That's technically a BC break, because there's code out there relying on chr() implicitly doing & 0xFF on the passed param. I think that's rather a doc bug? ------------------------------------------------------------------------ [2015-06-23 07:22:19] ab@php.net Description: ------------ When passing an integer that overflows PHP_INT_MAX in 32-bit, the behavior of chr() differs. The documentation currently doesn't define what should happen in this situation, the only statement is that chr() expects an ASCII code. chr() should ensure the input is in the valid range, thus making the behavior consistent between 32- and 64-bit. Test script: --------------- Debug\php.exe -r "$a = chr(2632627629); var_dump($a, ord($a));" string(1) " " int(0) x64\Debug\php.exe -r "$a = chr(2632627629); var_dump($a, ord($a));" string(1) "¡" int(173) Expected result: ---------------- string(1) " " int(0) Actual result: -------------- Different behavior depending on 32- or 64-bit build. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=69906&edit=1