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Re: [Bug-wget] bad filenames (again)

From: Eli Zaretskii
Subject: Re: [Bug-wget] bad filenames (again)
Date: Sun, 23 Aug 2015 17:47:07 +0300

> Date: Sun, 23 Aug 2015 16:15:04 +0200
> From: Ángel González <address@hidden>
> CC: address@hidden
> On 20/08/15 04:42, Eli Zaretskii wrote:
> >> From: Ángel González wrote:
> >>
> >> On 19/08/15 16:38, Eli Zaretskii wrote:
> >>> Indeed.  Actually, there's no need to allocate memory dynamically,
> >>> neither will malloc nor with alloca, since Windows file names have
> >>> fixed size limitation that is known in advance.  So each conversion
> >>> function can use a fixed-sized local wchar_t array.  Doing that will
> >>> also avoid the need for 2 calls to MultiByteToWideChar, the first one
> >>> to find out how much space to allocate.
> >> Nope. These functions would receive full path names, so there's no
> >> maximum length.*
> > Please see the URL I mentioned earlier in this thread: _all_ Windows
> > file-related APIs are limited to 260 characters, including the drive
> > letter and all the leading directories.
> Wrong. I can work with a larger one by using a UNC path.

But then you will be unable to use relative file names, and will have
to convert all the file names to the UNC format by hand, and any file
names we create that exceed the 260-character limit will be almost
unusable, since almost any program will be unable to
read/write/delete/copy/whatever it.  So this method is impractical,
and it doesn't lift the limit anyway, see below.

> >> * _Some_ Windows when using _some_ filesystems / apis have fixed limits,
> >> but there are ways to produce larger paths...
> > The issue here is not whether the size limits differ, the issue is
> > whether the largest limit is still fixed.  And it is, on Windows.
> I had tried to skip over the specific details in my previous mail. I 
> didn't meant that
> the limit would be bigger, but that there isn't one (that you can rely 
> on, at least). On
> Windows 95/98 you had this 260 character limit, and you currently still 
> do depending
> on the API you are using. But that's not a system limit any more.

This is wrong, and the URL I posted clearly describes the limitation:
If you use UNCs, the size is still limited to 32K characters.  So even
if we want to convert every file name to the UNC \\?\x:\foo\bar form
and create unusable files (which I don't recommend), the maximum
length is still known in advance.

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