Re: [Bug-wget] Query about correcting for DST with Wget

[Eli Zaretskii]

> Date: Sun, 13 Nov 2016 21:39:32 +0100
> From: Jernej Simončič <jernej|address@hidden>
> 
> On Sunday, November 13, 2016, 19:53:06, Eli Zaretskii wrote:
> 
> > Does "while DST is in effect" mean that you download the file when DST
> > is in effect, or you examine the timestamp of the file when the DST is
> > in effect?
> 
> I download the file when DST is(n't) in effect (I download that
> specific URL quite often, on different computers).

Then yes, it's a known problem with how the MS-Windows implementation
of the utimes function works: it converts (internally) from local time
to UTC using the current setting of the DST flag, not its setting at
the time being converted.  The irony of this is that there should be
no need to go through local time in this case, because the timestamp
provided by Wget is in UTC to begin with, and the low-level Windows
APIs that timestamp files accept UTC values.

If we care about this, we could have a private implementation of
utimes in mswindows.c, which would DTRT in the use cases needed by
Wget.

> I just remembered that there may be a 3rd explanation: some msvcrt
> functions return different timestamps depending on whether DST is in
> effect or not - at least with GIMP you can observe that it'll rescan
> all fonts the first time it's run after DST change (I'm not sure if
> this applies only to msvcrt.dll [which MinGW uses by default], or also
> to the runtimes shipped with newer Visual Studio versions).

You are talking about 'stat', I believe.  Yes, they, too, have a
similar bug, but 'stat' is not involved in the code in Wget that sets
the timestamps of downloaded files.