A NOTE has been added to this issue. ====================================================================== https://austingroupbugs.net/view.php?id=708 ====================================================================== Reported By: dalias Assigned To: ====================================================================== Project: 1003.1(2013)/Issue7+TC1 Issue ID: 708 Category: System Interfaces Type: Enhancement Request Severity: Editorial Priority: normal Status: New Name: Rich Felker Organization: musl libc User Reference: Section: XSH 2.9.1 Thread-Safety Page Number: unknown Line Number: unknown Interp Status: --- Final Accepted Text: ====================================================================== Date Submitted: 2013-06-07 21:23 UTC Last Modified: 2023-01-26 12:11 UTC ====================================================================== Summary: Make mblen, mbtowc, and wctomb thread-safe for alignment with C11 ======================================================================
---------------------------------------------------------------------- (0006139) geoffclare (manager) - 2023-01-26 12:11 https://austingroupbugs.net/view.php?id=708#c6139 ---------------------------------------------------------------------- In the January 2023 ballot resolution meeting, WG14 agreed to change (in C23) the requirement for these functions to avoid data races. At the moment their plan is to make it implementation-defined, but it is possible someone may submit a paper for consideration at the next meeting along the lines of N2281 but with wording changes to address the points raised in the discussion quoted in https://austingroupbugs.net/view.php?id=708#c5933. So we should leave this bug open pending a final decision by WG14, but what goes into C23 will likely only affect what we put in rationale and future directions in Issue 8, so we could start discussion at least on the normative text. I propose the following: In all of these changes the placeholder <i>XXXX</i> should be replaced with the name of the function. Page and line numbers are for Issue 8 draft 2.1. On page 1274 line 42635 section mblen(), and page 1285 line 42996 section mbtowc(), and page 2255 line 72488 section wctomb(), change:<blockquote>The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-202x defers to the ISO C standard.</blockquote>to:<blockquote>Except for requirements relating to data races, the functionality described on this reference page is aligned with the ISO C standard. Any other conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-202x defers to the ISO C standard for all <i>XXXX</i>() functionality except in relation to data races.</blockquote> On page 1274 line 42652 section mblen(), and page 1285 line 43015 section mbtowc(), and page 2255 line 72505 section wctomb(), change:<blockquote>[CX]The <i>XXXX</i>() function need not be thread-safe.[/CX]</blockquote>to:<blockquote>The <i>XXXX</i>() function [CX]need not be thread-safe; however, it[/CX] shall avoid data races with all other functions.</blockquote> On page 1274 line 42669 section mblen(), and page 1286 line 43032 section mbtowc(), and page 2255 line 72522 section wctomb(), change RATIONALE from "None" to:<blockquote>When the ISO C standard introduced threads in C11, it required <i>XXXX</i>() to avoid data races (with itself as well as with other functions), whereas POSIX.1-2008 did not require it to be thread-safe, and in many implementations it did not avoid data races with itself and still does not. The ISO C committee intend to change the requirements in C23, but since POSIX.1 currently refers to C17 it is necessary for it not to defer to the ISO C standard regarding data races in order to continue to allow this function not to avoid data races with itself.</blockquote> On page 1274 line 42669 section mblen(), and page 1286 line 43034 section mbtowc(), and page 2256 line 72524 section wctomb(), change FUTURE DIRECTIONS from "None" to:<blockquote>It is expected that a change in C23 will allow a future version of this standard to remove the data race exception from the statement that it defers to the ISO C standard.</blockquote> Issue History Date Modified Username Field Change ====================================================================== 2013-06-07 21:23 dalias New Issue 2013-06-07 21:23 dalias Name => Rich Felker 2013-06-07 21:23 dalias Organization => musl libc 2013-06-07 21:23 dalias Section => XSH 2.9.1 Thread-Safety 2013-06-07 21:23 dalias Page Number => unknown 2013-06-07 21:23 dalias Line Number => unknown 2013-06-08 09:12 geoffclare Note Added: 0001647 2013-06-08 09:13 geoffclare Tag Attached: C11 2013-06-08 12:14 dalias Note Added: 0001648 2013-06-13 15:35 nick Note Added: 0001651 2013-12-03 21:09 torvald Issue Monitored: torvald 2022-08-15 15:11 nick Note Added: 0005933 2023-01-26 12:11 geoffclare Note Added: 0006139 ======================================================================
