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

Edit report at https://bugs.php.net/bug.php?id=78627&edit=1 ID: 78627 Comment by: benjamin at betti dot me 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: Hi, It is not reproduced by 3v4l's "eval()" functionality, but it does actually happen with their live shell, as with 7.2.20+ and 7.3.7+ docker images (but not with 7.2.19- nor 7.3.6-). Not sure if it comes from php or from some libraries/dependancies bundled in the images. From 3v4l's live shell: ----------------------- PHP 7.3.0 (cli) (built: Dec 7 2018 10:59:04) ( NTS ) Copyright (c) 1997-2018 The PHP Group Zend Engine v3.3.0-dev, Copyright (c) 1998-2018 Zend Technologies Interactive shell php > $dist = sin(deg2rad(45.9007)) * sin(deg2rad(45.9007)) + cos(deg2rad(45.9007)) * cos(deg2rad(45.9007)); php > var_dump($dist, acos($dist)); float(1) float(NAN) https://i.imgur.com/hefGoU8.png From docker images: ------------------- benjamin@ontracks-benjamin  docker pull php:7.2.19 7.2.19: Pulling from library/php [...] Digest: sha256:977a074d8fe3e7c7647223cadca37d48d166abd82218fea270a96dfbebb74bb4 Status: Downloaded newer image for php:7.2.19 benjamin@ontracks-benjamin  docker run -it php:7.2.19 bash root@89f076974e21:/# uname -a Linux 89f076974e21 5.0.0-29-generic #31-Ubuntu SMP Thu Sep 12 13:05:32 UTC 2019 x86_64 GNU/Linux root@89f076974e21:/# php -v PHP 7.2.19 (cli) (built: Jul 3 2019 21:16:39) ( NTS ) Copyright (c) 1997-2018 The PHP Group Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies root@89f076974e21:/# php -a Interactive shell php > $dist = sin(deg2rad(45.9007)) * sin(deg2rad(45.9007)) + cos(deg2rad(45.9007)) * cos(deg2rad(45.9007)); php > var_dump($dist, acos($dist)); float(1) float(0) benjamin@ontracks-benjamin  docker pull php:7.2.20 7.2.20: Pulling from library/php [...] Digest: sha256:fddc1d9129c3fd84c0d95d1008d26c4c5284b9c8bc8e4a2983b1c0e421489423 Status: Downloaded newer image for php:7.2.20 benjamin@ontracks-benjamin  docker run -it php:7.2.20 bash root@ce8a5edd8426:/# uname -a Linux ce8a5edd8426 5.0.0-29-generic #31-Ubuntu SMP Thu Sep 12 13:05:32 UTC 2019 x86_64 GNU/Linux root@ce8a5edd8426:/# php -v PHP 7.2.20 (cli) (built: Jul 12 2019 23:20:54) ( NTS ) Copyright (c) 1997-2018 The PHP Group Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies root@ce8a5edd8426:/# php -a Interactive shell php > $dist = sin(deg2rad(45.9007)) * sin(deg2rad(45.9007)) + cos(deg2rad(45.9007)) * cos(deg2rad(45.9007)); php > var_dump($dist, acos($dist)); float(1) float(NAN) benjamin@ontracks-benjamin  docker pull php:7.3.6 7.3.6: Pulling from library/php fc7181108d40: Already exists [...] Digest: sha256:85b571a9138847f1a45ab29bc6f92a6ad3c7460e929e2ccc8b1035870984408d Status: Downloaded newer image for php:7.3.6 benjamin@ontracks-benjamin  docker run -it php:7.3.6 bash root@919a1affaa36:/# uname -a Linux 919a1affaa36 5.0.0-29-generic #31-Ubuntu SMP Thu Sep 12 13:05:32 UTC 2019 x86_64 GNU/Linux root@919a1affaa36:/# php -v PHP 7.3.6 (cli) (built: Jul 3 2019 20:46:48) ( NTS ) Copyright (c) 1997-2018 The PHP Group Zend Engine v3.3.6, Copyright (c) 1998-2018 Zend Technologies root@919a1affaa36:/# php -a Interactive shell php > $dist = sin(deg2rad(45.9007)) * sin(deg2rad(45.9007)) + cos(deg2rad(45.9007)) * cos(deg2rad(45.9007)); php > var_dump($dist, acos($dist)); float(1) float(0) benjamin@ontracks-benjamin  docker pull php:7.3.7 7.3.7: Pulling from library/php [...] Digest: sha256:9016d75d6aaa61da443f42cdf7e97994ecb4e1ceb94aeb6496dcf51cdaf132a2 Status: Downloaded newer image for php:7.3.7 benjamin@ontracks-benjamin  docker run -it php:7.3.7 bash root@2ee685f149d8:/# uname -a Linux 2ee685f149d8 5.0.0-29-generic #31-Ubuntu SMP Thu Sep 12 13:05:32 UTC 2019 x86_64 GNU/Linux root@2ee685f149d8:/# php -v PHP 7.3.7 (cli) (built: Jul 12 2019 22:25:55) ( NTS ) Copyright (c) 1997-2018 The PHP Group Zend Engine v3.3.7, Copyright (c) 1998-2018 Zend Technologies root@2ee685f149d8:/# php -a Interactive shell php > $dist = sin(deg2rad(45.9007)) * sin(deg2rad(45.9007)) + cos(deg2rad(45.9007)) * cos(deg2rad(45.9007)); php > var_dump($dist, acos($dist)); float(1) float(NAN) Previous Comments: ------------------------------------------------------------------------ [2019-10-03 10:35:16] cmb@php.net Cannot reproduce: <https://3v4l.org/LTLAg>. ------------------------------------------------------------------------ [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