Bug #78265 [Opn->Nab]: printf does not properly format decimals when using '%.8F'

Edit report at https://bugs.php.net/bug.php?id=78265&edit=1 ID: 78265 Updated by: cmb@php.net Reported by: mmucklo at gmail dot com Summary: printf does not properly format decimals when using '%.8F' -Status: Open +Status: Not a bug Type: Bug Package: I18N and L10N related Operating System: Linux / any PHP Version: 7.3.7 -Assigned To: +Assigned To: cmb Block user comment: N Private report: N New Comment: Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.php.net/manual/ and the instructions on how to report a bug at http://bugs.php.net/how-to-report.php See <https://www.php.net/manual/en/function.printf.php#refsect1-function.printf-parameters>. Previous Comments: ------------------------------------------------------------------------ [2019-07-09 06:43:17] mmucklo at gmail dot com Description: ------------ printf does not properly format uppercase floats. This is in the master branch and goes as far back as 5.6.40, but I didn't trace back any further. The problem code is here: https://github.com/php/php-src/blob/master/main/spprintf.c#L639 It only pays attention to a lower case 'f' WARNING - FIXING this could cause unsuspected results as this bug has been present as far back as 5.6.40 at least (the furthest back I looked). Specifically the code in microtime calls into the printf function (eventually), and this will change the output of microtime() to be locale-specific. https://github.com/php/php-src/blob/master/ext/standard/microtime.c#L81 This is not necessarily a bad thing, but there are perhaps libraries that expect the buggy behavior at this point (e.g. one that I presently maintain: https://github.com/mmucklo/DtcQueueBundle/blob/5.0.0/Util/Util.php#L104-L105) I'm not suggesting that it should not get fixed, but just to be cautious maybe where in the release cycle such a patch should go. As a reference (couldn't instantly find a C version, but this CPP version seems accurate): http://www.cplusplus.com/reference/cstdio/printf/ Also this Stackoverflow seems to clarify things. Pay particular attention to the second answer (about nan and inf capitalization), as I think PHP may do that wrong as well, although I didn't test it, but just looking at the code in spprintf.c, I don't see any specific logic to handle that case. https://stackoverflow.com/questions/34706228/difference-between-upper-and-lower-case-double-float-type-specifiers-in-c Test script: --------------- <?php // NOTE your system needs to have this locale loaded first // On ubuntu 19 which I'm using (via docker) do the following // from the shell prompt (if you are not root, become root, or prefix with sudo): // // locale-gen de_DE // locale-gen de_DE.UTF-8 // dpkg-reconfigure locales // // # you may also need the locales package installed (apt install locales). // $loc_de = setlocale(LC_ALL, 'de_DE.UTF-8', 'de_DE', 'de', 'ge'); printf("%0.8f\n", 0.12345); printf("%0.8F\n", 0.12335); // One should show the comma, the other won't /** Here is some C code to reproduce the expected result #include <stdio.h> #include <locale.h> int main(int argc, char**argv) { setlocale(LC_ALL, "de_DE.UTF-8"); printf("%.8f\n", 0.12345); printf("%.8F\n", 0.12335); return 0; } */ Expected result: ---------------- 0,12345000 0,12335000 Actual result: -------------- 0,12345000 0.12335000 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=78265&edit=1