Bug #78627 [Opn]: acos(1) is giving NAN instead of 0

Edit report at https://bugs.php.net/bug.php?id=78627&edit=1 ID: 78627 Updated by: cmb@php.net Reported by: me at gmorel dot io Summary: acos(1) is giving NAN instead of 0 Status: Open Type: Bug Package: *Math Functions Operating System: Linux Debian PHP Version: 7.2.23 Block user comment: N Private report: N New Comment: Cannot reproduce: <https://3v4l.org/LTLAg>. Previous Comments: ------------------------------------------------------------------------ [2019-10-03 10:10:45] me at gmorel dot io Description: ------------ --- From manual page: https://php.net/function.acos --- Hi, Thanks for all your work. Since the PHP 7.2.20 the acos function seems to have a regression. We have first isolated the bug in 7.2.23 In the case of $dist = sin(deg2rad(45.9007)) * sin(deg2rad(45.9007)) + cos(deg2rad(45.9007)) * cos(deg2rad(45.9007)); Before acos($dist) => 0 After acos($dist) => NAN uname -a Linux 609379a2965b 5.0.0-29-generic #31-Ubuntu SMP Thu Sep 12 13:05:32 UTC 2019 x86_64 GNU/Linux php -v PHP 7.2.23 (cli) (built: Sep 26 2019 23:37:50) ( NTS ) Copyright (c) 1997-2018 The PHP Group Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies with Zend OPcache v7.2.23, Copyright (c) 1999-2018, by Zend Technologies with Xdebug v2.7.2, Copyright (c) 2002-2019, by Derick Rethans php -m [PHP Modules] Core ctype curl date dom fileinfo filter ftp hash iconv json libxml mbstring mysqlnd openssl pcre PDO pdo_sqlite Phar posix readline Reflection session SimpleXML sodium SPL sqlite3 standard tokenizer xml xmlreader xmlwriter zlib [Zend Modules] ​Keep up the good work ​ Test script: --------------- PHP 7.2.18 (sorry they didn't have 7.2.19) http://sandbox.onlinephpfunctions.com/code/e59e94fa7aee04d67cbacf2990773c1658e4d1c2 It seems to have no issue in 7.3.5 But it appears also in 7.3.10 (cli) Expected result: ---------------- $dist = sin(deg2rad(45.9007)) * sin(deg2rad(45.9007)) + cos(deg2rad(45.9007)) * cos(deg2rad(45.9007)); var_dump(acos($dist)); // float(0) Actual result: -------------- $dist = sin(deg2rad(45.9007)) * sin(deg2rad(45.9007)) + cos(deg2rad(45.9007)) * cos(deg2rad(45.9007)); var_dump(acos($dist)); // double(NAN) ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=78627&edit=1