Date: Wed, 27 Mar 2024 11:26:17 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-main@FreeBSD.org Subject: git: 7534109d13a6 - main - libc: Improve description of mktime() / timegm(). Message-ID: <202403271126.42RBQHcA003736@gitrepo.freebsd.org>
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The branch main has been updated by des: URL: https://cgit.FreeBSD.org/src/commit/?id=7534109d13a6cdb22e78d9d4c0a0cd5efd323c45 commit 7534109d13a6cdb22e78d9d4c0a0cd5efd323c45 Author: Dag-Erling Smørgrav <des@FreeBSD.org> AuthorDate: 2024-03-27 10:03:37 +0000 Commit: Dag-Erling Smørgrav <des@FreeBSD.org> CommitDate: 2024-03-27 10:03:37 +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 --- 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 698a63cfa73d..96b7f775535a 100644 --- a/lib/libc/stdtime/ctime.3 +++ b/lib/libc/stdtime/ctime.3 @@ -27,7 +27,7 @@ .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" -.Dd April 20, 2023 +.Dd March 26, 2024 .Dt CTIME 3 .Os .Sh NAME @@ -241,7 +241,21 @@ 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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