Date: Thu, 4 Apr 2024 11:38:47 GMT From: Dag-Erling =?utf-8?Q?Sm=C3=B8rgrav?= <des@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: fdde01c5b449 - stable/14 - libc: Improve description of mktime() / timegm(). Message-ID: <202404041138.434BclUj059649@gitrepo.freebsd.org>
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The branch stable/14 has been updated by des: URL: https://cgit.FreeBSD.org/src/commit/?id=fdde01c5b44904e34ff3b003f446644de865fa21 commit fdde01c5b44904e34ff3b003f446644de865fa21 Author: Dag-Erling Smørgrav <des@FreeBSD.org> AuthorDate: 2024-03-27 10:03:37 +0000 Commit: Dag-Erling Smørgrav <des@FreeBSD.org> CommitDate: 2024-04-04 09:41:41 +0000 libc: Improve description of mktime() / timegm(). * Mention that mktime() and timegm() set errno on failure. * Correctly determining whether mktime() / timegm() succeeded with arbitrary input (where -1 can be a valid result) is non-trivial. Document the recommended procedure. PR: 277863 MFC after: 1 week Reviewed by: pauamma_gundo.com, gbe Differential Revision: https://reviews.freebsd.org/D44503 (cherry picked from commit 7534109d13a6cdb22e78d9d4c0a0cd5efd323c45) --- lib/libc/stdtime/ctime.3 | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/lib/libc/stdtime/ctime.3 b/lib/libc/stdtime/ctime.3 index 25a7c6a7656e..7216ada23826 100644 --- a/lib/libc/stdtime/ctime.3 +++ b/lib/libc/stdtime/ctime.3 @@ -29,7 +29,7 @@ .\" .\" From: @(#)ctime.3 8.1 (Berkeley) 6/4/93 .\" -.Dd April 20, 2023 +.Dd March 26, 2024 .Dt CTIME 3 .Os .Sh NAME @@ -243,7 +243,21 @@ The .Fn mktime function returns the specified calendar time; if the calendar time cannot be -represented, it returns \-1; +represented, it returns \-1 and sets +.Xr errno 3 +to an appropriate value. +.Pp +Note that \-1 is a valid result (representing one second before +midnight UTC on the evening of 31 December 1969), so this cannot be +relied upon to indicate success or failure; instead, +.Fa tm_wday +and / or +.Fa tm_yday +should be set to an out-of-bounds value (e.g. \-1) prior to calling +.Fn mktime +or +.Fn timegm +and checked after the call. .Pp The .Fn difftime
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