Last modified: 2014-10-08 05:42:34 UTC
For example: - converting '0x10' from base36 to base36 results in '000g' instead of '0x10' - converting '0x1234567890abhaer' from base36 to base36 returns '000000000000000000, and raises this warning: "Warning: gmp_init(): Unable to convert variable to GMP - wrong type! in /home/fredemmott/test2.php on line 3"; presumably this is because 'h' isn't valid in an executable string Tested with PHP 5.5.9 and HHVM 3.2.0 against Mediawiki master and 1.22wmf22 Isolated examples showing the cause: <?php $in = '0x1234567890abhaer'; $gmp = gmp_init($in, 36); $val = gmp_strval($gmp, 36); var_dump(str_pad($val, strlen($in), '0', STR_PAD_LEFT)); <?php $in = '0x10'; $gmp = gmp_init($in, 36); $val = gmp_strval($gmp, 36); var_dump(str_pad($val, strlen($in), '0', STR_PAD_LEFT)); This issue was found by WfBaseConvertTest::testIdentity intermittently failing on HHVM's CI system since we added GMP support. Cause found by fuzzing: <?php function test() { $chars = '0123456789abcdefghijklmnopqrstuvwxyz'; $base = mt_rand(2, 36); $len = mt_rand(10, 100); $str = ''; for ($i = 0; $i < $len; ++$i) { $str .= $chars[mt_rand(0, $base - 1)]; } $gmp = gmp_init($str, $base); $val = gmp_strval($str, $base); $val = str_pad($val, strlen($str), '0', STR_PAD_LEFT); if ($val !== $str) { throw new Exception('Not same - base '.$base."\n-".$str."\n+".$val); } } for($i = 0; $i < 100000; ++$i) { test(); }
s/executable string/hexadecimal string/... oops.
Thanks for taking the time to report this! Note to myself: includes/GlobalFunctions.php in Core. CC'ing Aaron as he's worked on wfBaseConvert before.
Just to be clear re the hiphop keyword: this bug also exists if using PHP5 with the gmp extension.
I think this is a case where gmp_init() is not behaving as documented on php.net. ltrim( $input, '0' ) should suffice as a workaround. The documentation: The base may vary from 2 to 36. If base is 0 (default value), the actual base is determined from the leading characters: if the first two characters are 0x or 0X, hexadecimal is assumed, otherwise if the first character is "0", octal is assumed, otherwise decimal is assumed. [It doesn't say "if and only if", though there is no mention of autodetection when base is not 0.] PHP 5.6, from convert_to_gmp() in ext/gmp/gmp.c: if (Z_STRLEN_P(val) > 2) { if (numstr[0] == '0') { if (numstr[1] == 'x' || numstr[1] == 'X') { base = 16; skip_lead = 1; } else if (base != 16 && (numstr[1] == 'b' || numstr[1] == 'B')) { base = 2; skip_lead = 1; } } } [Why is this code even present when simply leaving it out, according to the GMP documentation <https://gmplib.org/manual/Assigning-Integers.html#Assigning-Integers>, would produce the documented behavior?] HHVM, from variantToGMPData(): //Figure out what Base to use based on the ~*data*~ if (strLength > 1 && dataString[0] == '0') { if (strLength > 2) { if (dataString[1] == 'x' || dataString[1] == 'X') { base = 16; dataString = dataString.substr(2); } else if (base < 12 && (dataString[1] == 'b' || dataString[1] == 'B')) { base = 2; dataString = dataString.substr(2); } } if (base == -1) { base = 8; } } else if (strLength == 0) { dataString = s_gmp_0.get(); } if (base == -1) { base = GMP_DEFAULT_BASE; } [Also note the use of -1 rather than 0 for autodetect.]
This is a very old bug in PHP, likely caused by the following commit: https://github.com/php/php-src/commit/cc065b33514a3ef6533de6b5406db954a5f4b9c4 Notice that the base == 0 check was lost. Then the committer noticed a problem and "fixed" it: https://github.com/php/php-src/commit/6829710dceb0d39a06b7560a493a462e7504657b
https://bugs.php.net/bug.php?id=50175 https://bugs.php.net/bug.php?id=55398
(In reply to Kevin Israel (PleaseStand) from comment #6) > https://bugs.php.net/bug.php?id=50175 > https://bugs.php.net/bug.php?id=55398 Fixed for PHP 5.6.1. Just have to fix HHVM and add a workaround to MediaWiki for older PHP versions.
Change 157870 had a related patch set uploaded by PleaseStand: wfBaseConvert(): Work around PHP Bug #50175 https://gerrit.wikimedia.org/r/157870
Change 157870 merged by jenkins-bot: wfBaseConvert(): Work around PHP Bug #50175 https://gerrit.wikimedia.org/r/157870
Kudos, Kevin.
