A NOTE has been added to this issue. ====================================================================== https://austingroupbugs.net/view.php?id=1302 ====================================================================== Reported By: geoffclare Assigned To: ====================================================================== Project: 1003.1(2016/18)/Issue7+TC2 Issue ID: 1302 Category: Base Definitions and Headers Type: Enhancement Request Severity: Objection Priority: normal Status: New Name: Geoff Clare Organization: The Open Group User Reference: Section: (many) Page Number: (many) Line Number: (many) Interp Status: --- Final Accepted Text: ====================================================================== Date Submitted: 2019-11-19 15:27 UTC Last Modified: 2020-11-08 23:42 UTC ====================================================================== Summary: Alignment with C17 ====================================================================== Relationships ID Summary ---------------------------------------------------------------------- related to 0000411 adding atomic FD_CLOEXEC support related to 0000711 Are the stdarg.h macros async-signal-safe? related to 0001163 fscanf omits carriage in the list of wh... ======================================================================
---------------------------------------------------------------------- (0005108) nick (manager) - 2020-11-08 23:42 https://austingroupbugs.net/view.php?id=1302#c5108 ---------------------------------------------------------------------- The following issue was pointed out by Hubert Tong in response to a request for comments on the current draft to the C committee: ==================== C17 and POSIX wording issues for pow() domain errors for IEC 60559 (MX) In C17 subclause 7.12.7.4 paragraph 2, regarding the pow() function: A domain error occurs if x is finite and negative and y is finite and not an integer value. This is not consistent with subclause F.10.4.4 if -0 is negative. A similar, more extensive problem, is present for POSIX. The ERRORS section for pow() in POSIX.1-2017 XSH Chapter 3 indicates that a Domain Error shall occur when "[the] value of x is negative and y is a finite non-integer". See https://pubs.opengroup.org/onlinepubs/9699919799/functions/pow.html However, the RETURN VALUE section of the same says: For y > 0 and not an odd integer, if x is ±0, +0 shall be returned. For y < 0 and not an odd integer, if x is -Inf, +0 shall be returned. For y > 0 and not an odd integer, if x is -Inf, +Inf shall be returned. I would prefer for an implementation to be allowed to "report success" when it provides the specified return value (regardless of whether it provides the specified return value for other inputs). What C17 says itself is likely wrong for -0. I believe I have pointed out a self-inconsistency in POSIX: the optional behaviour specifies that there is an exact, non-NaN value to return. When such a value is returned, there should be no error condition. >From IEEE 754: Attempts to evaluate a function outside its domain shall return a quiet NaN and signal the invalid operation exception. Thus POSIX is both saying that it is non-optional for pow(-Inf, 0.5) to report an error and that it may optionally return +Inf (which is a return value not indicative of an error). The change to correct this would be to update the ERRORs section to express that the specified error only occurs when the implementation does not return the value indicated for the optional behaviour in the RETURN VALUE section Issue History Date Modified Username Field Change ====================================================================== 2019-11-19 15:27 geoffclare New Issue 2019-11-19 15:27 geoffclare File Added: C17_alignment_20191119.pdf 2019-11-19 15:27 geoffclare Name => Geoff Clare 2019-11-19 15:27 geoffclare Organization => The Open Group 2019-11-19 15:27 geoffclare Section => (many) 2019-11-19 15:27 geoffclare Page Number => (many) 2019-11-19 15:27 geoffclare Line Number => (many) 2019-11-19 15:27 geoffclare Interp Status => --- 2019-11-19 17:04 shware_systems Note Added: 0004663 2019-11-20 09:16 geoffclare Note Added: 0004664 2019-11-20 10:49 dennisw Note Added: 0004665 2019-11-20 14:07 geoffclare Note Added: 0004666 2019-11-20 15:41 geoffclare Relationship added related to 0000411 2019-11-20 15:42 geoffclare Relationship added related to 0000711 2019-11-20 15:42 geoffclare Relationship added related to 0001163 2020-11-02 11:49 geoffclare File Added: C17_alignment_20201102.pdf 2020-11-02 11:50 geoffclare File Added: C17_alignment_20201102_diffs.pdf 2020-11-02 11:57 geoffclare Note Added: 0005093 2020-11-02 12:01 geoffclare Note Edited: 0005093 2020-11-08 23:42 nick Note Added: 0005108 ======================================================================
