Odd, is it not? mkdir 'e:\' cannot be undone by rmdir 'e:\' ...

Thu Sep 19 19:51:00 GMT 2019

On 9/1/2019 1:38 PM, Houder wrote:
> On 2019年8月30日 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円'; <==== 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円' 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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