From: Ken Brown <kbrown@cornell.edu>
To: "cygwin@cygwin.com" <cygwin@cygwin.com>
Subject: Re: Odd, is it not? mkdir 'e:\' cannot be undone by rmdir 'e:\' ...
Date: Thu, 19 Sep 2019 19:51:00 -0000 [thread overview]
Message-ID: <f77b318f-0c52-4b5f-3738-ff882804e84a@cornell.edu> (raw)
In-Reply-To: <e438666b60ee08a2a3ee4ca16015382f@smtp-cloud9.xs4all.net>
On 9/1/2019 1:38 PM, Houder wrote:
> On Fri, 30 Aug 2019 11:54:27, Houder wrote:
[...]
> As the directory "/foo" had been correctly created, I turned to
> path_conv::check(), which is called when build_fhname() creates
> the path_conv object (also called pc) -- see dtable.cc.
>
> Examining this (obsure) method in path.cc, I corrected the code
> in 2 places:
>
> ---
> if (dev.isfs ())
> {
> //if (strncmp (path, "\\\\.\\", 4)) <==== 1171
> if ( ! strncmp (path, "\\\\.\\", 4)) // <==== [1]
> {
> if (!tail || tail == path)
> /* nothing */;
> else if (tail[-1] != '\\')
> *tail = '\0'; <==== Ah! (you should not do that!)
> else
> {
> error = ENOENT;
> return;
> }
> }
>
> [1] this code should be executed only if path == '\\.\' !!
I don't agree with your analysis here.
First, the strncmp() call is testing whether path *starts with* '\\.\', not
whether path == '\\.\'. For example, path might be a UNC device name like
'\\.\c:'. Second, as the original code indicates (before your correction), we
do *not* want to execute the code in that case, since we might be mutilating the
device name or incorrectly setting ENOENT.
On the other hand, I agree that there's something wrong with that code snippet.
Comparing tail with path [which is the class member this->path] makes no sense
here, because tail is a pointer into path_copy. So I think line 1173 should read
if (!tail || tail == path_copy)
If this condition fails, then it's legitimate to refer to tail[-1] two lines later.
Observe next that path_copy contains no backslashes, so I think line 1175 should
probably be
else if (tail[-1] != '/')
I don't immediately see why we would then set *tail = '\0' in this case, because
I think *tail is already 0 if we get here and tail[-1] != '/'. But maybe I'm
missing something.
I need to think about this further, but I wanted to write down my initial
thoughts before your bug report gets forgotten.
To be continued.
Ken
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next prev parent reply other threads:[~2019-09-19 18:04 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-27 15:25 Houder
2019-08-27 16:28 ` Corinna Vinschen
2019-08-27 17:01 ` Houder
2019-08-27 17:32 ` Vince Rice
2019-08-27 17:50 ` Corinna Vinschen
2019-08-28 7:16 ` Houder
2019-08-28 9:22 ` john doe
2019-08-28 11:47 ` Houder
2019-08-28 13:22 ` Corinna Vinschen
2019-08-28 14:16 ` Eric Blake
2019-08-28 14:22 ` Corinna Vinschen
2019-08-28 15:18 ` Corinna Vinschen
2019-08-29 15:19 ` Houder
2019-08-30 8:20 ` Corinna Vinschen
2019-08-30 12:42 ` Houder
2019-09-01 17:38 ` Houder
2019-09-02 8:15 ` Corinna Vinschen
2019-09-03 8:40 ` Houder
2019-09-03 6:50 ` Andrey Repin
2019-09-19 19:51 ` Ken Brown [this message]
2019-09-20 9:11 ` Houder
2019-09-20 18:20 ` Houder
2019-09-21 16:07 ` Ken Brown
2019-09-22 7:34 ` Houder
2019-09-22 14:12 ` Ken Brown
2019-09-07 3:47 ` L A Walsh
2019-08-27 19:48 ` Achim Gratz
2019-08-27 20:58 ` Brian Inglis
2019-08-28 7:16 ` Corinna Vinschen
2019-08-27 22:21 ` Achim Gratz
2019-08-28 13:36 ` Eric Blake
2019-08-28 22:57 ` Houder
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