Branch: refs/heads/blead
Home: https://github.com/Perl/perl5
Commit: 4122b31e0427dd397297ef70a4bbd0b481ed7c92
https://github.com/Perl/perl5/commit/4122b31e0427dd397297ef70a4bbd0b481ed7c92
Author: Karl Williamson <[email protected]>
Date: 2026-01-12 (Mon, 12 Jan 2026)
Changed paths:
M ext/POSIX/t/posix.t
Log Message:
-----------
posix.t: Properly populate optional fields to strtime
The next commits that fix some bugs showed these were not properly
getting initialized.
Commit: a003be9e734d307931413a1f62ec479b6919f477
https://github.com/Perl/perl5/commit/a003be9e734d307931413a1f62ec479b6919f477
Author: Karl Williamson <[email protected]>
Date: 2026-01-12 (Mon, 12 Jan 2026)
Changed paths:
M locale.c
Log Message:
-----------
locale.c: Silence unused variable compiler warning
On some systems this was unused. Now that we have C99, we can move the
declaration and some #ifdef's and not declare it unless it is going to
be used.
Commit: 7f9d1560104938657e9101b32f1f7f768f315a77
https://github.com/Perl/perl5/commit/7f9d1560104938657e9101b32f1f7f768f315a77
Author: Karl Williamson <[email protected]>
Date: 2026-01-12 (Mon, 12 Jan 2026)
Changed paths:
M locale.c
Log Message:
-----------
locale.c: Slight comment clarification
Commit: cf36e33dd6b30c3e88531cad1810f601654e6f46
https://github.com/Perl/perl5/commit/cf36e33dd6b30c3e88531cad1810f601654e6f46
Author: Karl Williamson <[email protected]>
Date: 2026-01-12 (Mon, 12 Jan 2026)
Changed paths:
M locale.c
Log Message:
-----------
locale.c: ints_to_tm: Fix #if's
tl;dr:
Fixes GH #23878
I botched this in Perl 5.42. These conditional compilation statements
were just plain wrong, causing code to be skipped that should have been
compiled. It only affected the few hours of the year when daylight
savings time is removed, so that the hour value is repeated. We didn't
have a good test for that.
gory details:
libc uses 'struct tm' to hold information about a given instant in
time, containing fields for things like the year, month, hour, etc. The
libc function mktime() is used to normalize the structure, adjusting,
say, an input Nov 31 to be Dec 01.
One of the fields in the structure, 'is_dst', indicates if daylight
savings is in effect, or whether that fact is unknown. If unknown,
mktime() is supposed to calculate the answer and to change 'is_dst'
accordingly. Some implementations appear to always do this calculation
even when the input value says the result is known. Others appear to
honor it.
Some libc implementations have extra fields in 'struct tm'.
Perl has a stripped down version of mktime(), called mini_mktime(),
written by Larry Wall a long time ago. I don't know why. This crippled
version ignores locale and daylight time. It also doesn't know about
the extra fields in 'struct tm' that some implementations have. Nor can
it be extended to know about those fields, as they are dependent on
timezone and daylight time, which it deliberately doesn't consider.
The botched #ifdef's were supposed to compensate for both the extra
fields in the struct and that some libc implementations always
recalculate 'is_dst'.
On systems with these fields, the botched #if's caused only
mini_mktime() to be called. This meant that these extra fields didn't
get populated, and daylight time is never considered to be in effect.
And 'is_dst' does not get changed from the input.
On systems without these fields, the regular libc mktime() would be
called appropriately.
The bottom line is that for the portion of the year when daylight
savings is not in effect, that portion worked properly. The two extra
fields would not be populated, so if some code were to read them, it
would only get the proper values by chance. We got no reports of this.
I attribute that to the fact that the use of these is not portable, so
code wouldn't tend to use them. There are portable ways to access the
information they contain.
Tests were failing for the portions of the year when daylight savings is
in effect; see GH #22351. The code looked correct just reading it (not
seeing the flaw in the #ifdef's), so I assumed that it was an issue in
the libc implementations and instituted a workaround. (I can't now
think of a platform where there hasn't been a problem with a libc with
something regarding locales, so that was a reasonable assumption.)
Among other things (fixed in the next commit), that workaround overrode
the 'is_dst' field after the call to mini_mktime(), so that the value
actually passed to libc strftime() indicated that daylight is in effect.
What happens next depends on the libc strftime() implementation. It
could conceivably itself call mktime() which might choose to override
is_dst to be the correct value, and everything would always work. The
more likely possibility is that it just takes the values in the struct
as-is. Remember that those values on systems with the extra fields were
calculated as if daylight savings wasn't in effect, but now we're
telling strftime() to use those values as if it were in effect. This
is a discrepancy. I'd have to trace through some libc implementations
to understand why this discrepancy seems to not matter except at the
transition time.
But the bottom line is this commit removes that discrepancy, and causes
mktime() to be called appropriately on systems where it wasn't, so
strftime() should now function properly.
Commit: 92a20ace82a0d76337278fc8065171a1cff3c50b
https://github.com/Perl/perl5/commit/92a20ace82a0d76337278fc8065171a1cff3c50b
Author: Karl Williamson <[email protected]>
Date: 2026-01-12 (Mon, 12 Jan 2026)
Changed paths:
M locale.c
Log Message:
-----------
my_strftime(): Properly take daylight savings into account
Because of the bug fixed in the previous commit, this function was
changed in 5.42 to have a work around, which is no longer needed.
Commit: f0096bdd935def721d49239e8911bcaf03c4a40e
https://github.com/Perl/perl5/commit/f0096bdd935def721d49239e8911bcaf03c4a40e
Author: Karl Williamson <[email protected]>
Date: 2026-01-12 (Mon, 12 Jan 2026)
Changed paths:
M ext/POSIX/POSIX.xs
M ext/POSIX/lib/POSIX.pm
Log Message:
-----------
POSIX.xs: Properly take daylight savings into account
Because of the bug fixed two commits ago, this function was changed in
5.42 to have a work around, which is no longer needed.
Commit: 93d62c0706b68fe1cfd1012e061011e814a455b6
https://github.com/Perl/perl5/commit/93d62c0706b68fe1cfd1012e061011e814a455b6
Author: Karl Williamson <[email protected]>
Date: 2026-01-12 (Mon, 12 Jan 2026)
Changed paths:
M ext/POSIX/t/time.t
Log Message:
-----------
POSIX/t/time.t: Extract common code to single place
Commit: 0ff7fef53ef3e1be49a249cd0d9e6819fc4c4926
https://github.com/Perl/perl5/commit/0ff7fef53ef3e1be49a249cd0d9e6819fc4c4926
Author: Karl Williamson <[email protected]>
Date: 2026-01-12 (Mon, 12 Jan 2026)
Changed paths:
M ext/POSIX/t/time.t
Log Message:
-----------
POSIX/t/time.t: tzset() works on Windows; not MingW
I ran some experiments, and found that tzset works on Windows, and is
required after changing the TZ environment variable from within perl.
But it did not work on MingW. Maybe there is something else needed in
the Posix module that would get it to work; I didn't investigate
The only way I could figure out how to distinguish in Perl space between
MSVC and MingW was looking at the make command. Maybe there is a better
way
Commit: ecba154a518b40b12d0527f9a9d95c44d8dad52b
https://github.com/Perl/perl5/commit/ecba154a518b40b12d0527f9a9d95c44d8dad52b
Author: Karl Williamson <[email protected]>
Date: 2026-01-12 (Mon, 12 Jan 2026)
Changed paths:
M ext/POSIX/t/time.t
Log Message:
-----------
POSIX/t/time.t: Add tests for DST changes
Commit: b5a88526275396057cb3fdb55657a2306d89f30a
https://github.com/Perl/perl5/commit/b5a88526275396057cb3fdb55657a2306d89f30a
Author: Karl Williamson <[email protected]>
Date: 2026-01-12 (Mon, 12 Jan 2026)
Changed paths:
M ext/POSIX/lib/POSIX.pod
M locale.c
Log Message:
-----------
perlapi: Add extensive strftime documentation
Due to the differences in various systems' implementations, I think it
is a good idea to more fully document the vagaries I have discovered,
and how perl resolves them.
Commit: 174ed799d45a2ef4e46a16779febe8130078e2f7
https://github.com/Perl/perl5/commit/174ed799d45a2ef4e46a16779febe8130078e2f7
Author: Karl Williamson <[email protected]>
Date: 2026-01-12 (Mon, 12 Jan 2026)
Changed paths:
M pod/perldelta.pod
Log Message:
-----------
perldelta for GH #23878
Compare: https://github.com/Perl/perl5/compare/6dc6bb9e401d...174ed799d45a
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