On Mar 29 19:34, LIU Hao wrote:
> 在 2023/3/29 16:40, Corinna Vinschen 写道:
> > > > No, this would allow splitting `\\host\\share` as `host` and `share`. In
> > > > this path the share name is `\share`, and does not match `share`.
> >
> > I was just pointing out that "\foo" can't be a share name, because
> > backslashes can't be part of a name.
> >
> > On second thought, maybe I don't understand what you were trying to say.
> > Can you rephrase, please?
>
> Apologies for the confusion.
>
> There was a mistake in the quote above, but the point in that message holds:
> `\\host\\share` is not a valid UNC path. If we allowed `dirname()` to remove
> the share name as a plain component, then, because `dirname()` treats
> consecutive separators as a single one, the result would be
>
> dirname("\\host\\share") = "\\host"
> basename("\\host\\share") = "share"
>
> which would be incorrect. "\\host\\share" is a UNC path with an empty share
> name (that's why it's invalid),
I don't think this is correct. Multiple backslashes are folded into a
single backslash by the Windows API layer. Thus \\host\\share is not
equivalent to
\\host\<empty-share>\<dir-called-share>
but to
\\host\share
Try this example, please:
$ cat > gfp.c <<EOF
#include <stdio.h>
#include <windows.h>
int
main (int argc, char **argv)
{
char buf[256];
GetFullPathNameA (argv[1], 256, buf, NULL);
printf ("%s\n", buf);
}
EOF
$ gcc -g -o gfp gfp.c
$ ./gfp '\\host\share'
\\host\share
$ ./gfp '\\host\\share'
\\host\share
$ ./gfp '\\host\\\share'
\\host\share
And here's the same for an existing share:
$ cat > gfp2.c <<EOF
#include <stdio.h>
#include <windows.h>
int
main (int argc, char **argv)
{
char buf[256];
HANDLE h;
h = CreateFileA (argv[1], GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL, OPEN_ALWAYS, FILE_FLAG_BACKUP_SEMANTICS, NULL);
if (h != INVALID_HANDLE_VALUE)
{
GetFinalPathNameByHandleA (h, buf, 256,
FILE_NAME_NORMALIZED | VOLUME_NAME_DOS);
printf ("%s\n", buf);
CloseHandle (h);
}
}
EOF
$ gcc -g -o gfp2 gfp2.c
$ ./gfp '\\calimero\corinna'
\\?\UNC\calimero\corinna
$ ./gfp '\\calimero\\corinna'
\\?\UNC\calimero\corinna
$ ./gfp '\\calimero\\\corinna'
\\?\UNC\calimero\corinna
> and we probably shouldn't make it
> indistinguishable from `\\host\share`. So it should be
>
> dirname("\\host\\share") = "\\host\"
> basename("\\host\\share") = "share"
>
>
> > Actually, the dirname function is not supposed to fold slashes (or
> > backslashes) at all, except at the start of the path. It's also not
> > supposed to throw any errors. It just cuts the path so that the last
> > path component is dropped.
>
> My point is that `\\host\share` is a volume name (the 'prefix', like `C:`)
> and is not made up of two components. `dirname()` is supposed to remove the
> last component, but there is no such component to remove.
Yes, that's a valid point. My point of view differs, but ultimately that
doesn't matter much.
Corinna
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