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From: Paul Eggert <eggert@cs.ucla.edu>
To: Bruno Haible <bruno@clisp.org>
Cc: bug-gnulib@gnu.org
Subject: Re: localtime on native Windows
Date: Sun, 18 Feb 2024 11:05:52 -0800	[thread overview]
Message-ID: <ffd7d3bb-ad22-426a-b948-8abee8ea0786@cs.ucla.edu> (raw)
In-Reply-To: <5188612.NACDBdzCOe@nimes>

On 2024-02-18 06:38, Bruno Haible wrote:
>    - How can the caller do the caching for something internal to the callee?

The caller calls tzalloc, gets a timezone object, and calls tzfree when 
it no longer needs that timezone object.

>   - The NetBSD code [1][2] does locking in the top-level functions (tzset,
>     mktime, strftime). I guess that it is because NetBSD uses global variables
>     (tzname, timezone, daylight, altzone).

This is for backward compatibility, and is required for POSIX 
compatibility. It has obvious problems with threads. New code should not 
use these vestigial interfaces. They should use localtime_z and 
mktime_z. (There should be no need for strftime_z.)


> For Gnulib, I intend to avoid global variables of this kind — they belong
> in data allocated for each time zone — and therefore move the locking to
> lower levels. In the frequent case that a timezone is used for the second
> time or later, no locking will be needed at all; this will thus be faster
> than what NetBSD does.

You're right to avoid the global variables, but I don't see why tzalloc 
needs to lock, even in MS-Windows. Perhaps there could be an "I'll do 
the caching" layer above tzalloc, but the lower-level code need not lock 
at all.

  reply	other threads:[~2024-02-18 19:06 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-09 17:43 MT-unsafe time modules Bruno Haible
2024-02-09 20:22 ` Bruno Haible
2024-02-10 11:10 ` Bruno Haible
2024-02-11 12:46   ` localtime on native Windows Bruno Haible
2024-02-13  2:02     ` Paul Eggert
2024-02-18  2:38       ` Bruno Haible
2024-02-18  4:50         ` Paul Eggert
2024-02-18 14:38           ` Bruno Haible
2024-02-18 19:05             ` Paul Eggert [this message]
2024-02-11 10:43 ` MT-unsafe time modules Bruno Haible
  -- strict thread matches above, loose matches on Subject: below --
2024-02-13 18:25 localtime on native Windows Brian Inglis
2024-02-18  2:14 ` Bruno Haible
2024-02-18  5:32   ` Brian.Inglis

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