cygwin_conv_path sometimes removes trailing slash

cygwin_conv_path sometimes removes trailing slash

[Ken Brown]

I'm using cygwin_conv_path to convert Win32 paths to POSIX paths, and 
I'm puzzled by the conversion

   d:/ --> /cygdrive/d

without the trailing slash.  By contrast, we have

   d:/foo/ --> /cygdrive/d/foo/

Is the removal of the trailing slash in the first example a deliberate 
design decision?  I find it counter-intuitive.

My tests are essentially based on the example at the end of 
https://cygwin.com/cygwin-api/func-cygwin-conv-path.html:

#include <sys/cygwin.h>
#include <stdio.h>
#include <stdlib.h>

int
main ()
{
   wchar_t *win32 = L"d:/";
   ssize_t size;
   char *posix;
   size = cygwin_conv_path (CCP_WIN_W_TO_POSIX, win32, NULL, 0);
   if (size < 0)
     perror ("cygwin_conv_path");
   else
     {
       posix = (char *) malloc (size);
       if (cygwin_conv_path (CCP_WIN_W_TO_POSIX, win32, posix, size))
	perror ("cygwin_conv_path");
     }
   printf ("%s\n", posix);
}

Ken

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Re: cygwin_conv_path sometimes removes trailing slash

[Jan Nijtmans]

2016-01-30 4:21 GMT+01:00 Ken Brown:
> I'm using cygwin_conv_path to convert Win32 paths to POSIX paths, and I'm
> puzzled by the conversion
>
>   d:/ --> /cygdrive/d
>
> without the trailing slash.  By contrast, we have
>
>   d:/foo/ --> /cygdrive/d/foo/

This came up before:
   <https://cygwin.com/ml/cygwin/2015-10/msg00048.html>
I had to workaround it in tkimg.

It's easy to workaround in your program, but - indeed -
that shouldn't be necessary. I too would expect that
when the input contains a slash, the output should too.

Regards,
     Jan Nijtmans

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Re: cygwin_conv_path sometimes removes trailing slash

[Henri]

Jan Nijtmans <jan.nijtmans <at> gmail.com> writes:

> 
> 2016-01-30 4:21 GMT+01:00 Ken Brown:
> > I'm using cygwin_conv_path to convert Win32 paths to POSIX paths, and I'm
> > puzzled by the conversion
> >
> >   d:/ --> /cygdrive/d
> >
> > without the trailing slash.  By contrast, we have
> >
> >   d:/foo/ --> /cygdrive/d/foo/
> 
> This came up before:
>    <https://cygwin.com/ml/cygwin/2015-10/msg00048.html>
> I had to workaround it in tkimg.
> 
> It's easy to workaround in your program, but - indeed -
> that shouldn't be necessary. I too would expect that
> when the input contains a slash, the output should too.
> 
> Regards,
>      Jan Nijtmans

For the record ...

 - Ken Brown refers to: win32 -> posix
 - Jan Nijthuis and Ray Donnelly refer to: posix -> win32

Different code paths ...

(and yes, conversions in both directions should be correct)

Regards,
Henri






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Re: cygwin_conv_path sometimes removes trailing slash

[Henri]

Henri <houder <at> xs4all.nl> writes:

> For the record ...
> 
>  - Ken Brown refers to: win32 -> posix
>  - Jan Nijthuis and Ray Donnelly refer to: posix -> win32
> 
> Different code paths ...
> 
> (and yes, conversions in both directions should be correct)

s/Nijthuis/Nijtmans/

Sigh.

Henri




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Re: cygwin_conv_path sometimes removes trailing slash

[Ray Donnelly]

On Mon, Feb 1, 2016 at 10:29 AM, Henri <houder@xs4all.nl> wrote:
> Jan Nijtmans <jan.nijtmans <at> gmail.com> writes:
>
>>
>> 2016-01-30 4:21 GMT+01:00 Ken Brown:
>> > I'm using cygwin_conv_path to convert Win32 paths to POSIX paths, and I'm
>> > puzzled by the conversion
>> >
>> >   d:/ --> /cygdrive/d
>> >
>> > without the trailing slash.  By contrast, we have
>> >
>> >   d:/foo/ --> /cygdrive/d/foo/
>>
>> This came up before:
>>    <https://cygwin.com/ml/cygwin/2015-10/msg00048.html>
>> I had to workaround it in tkimg.
>>
>> It's easy to workaround in your program, but - indeed -
>> that shouldn't be necessary. I too would expect that
>> when the input contains a slash, the output should too.
>>
>> Regards,
>>      Jan Nijtmans
>
> For the record ...
>
>  - Ken Brown refers to: win32 -> posix
>  - Jan Nijthuis and Ray Donnelly refer to: posix -> win32
>
> Different code paths ...
>
> (and yes, conversions in both directions should be correct)

I can't check as I'm at work, but to the best of my knowledge (and yes
I wrote these a long time ago) path_conv::check is used in conversions
both ways so I am talking about both cases here, Jan's with the first
patch and Ken's with the second patch. Please do correct me if I am
wrong though! I will run some detailed tests tonight.

Best regards,

Ray.

>
> Regards,
> Henri
>
>
>
>
>
>
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Re: cygwin_conv_path sometimes removes trailing slash

[Henri]

Ray Donnelly <mingw.android <at> gmail.com> writes:

> I can't check as I'm at work, but to the best of my knowledge (and yes
> I wrote these a long time ago) path_conv::check is used in conversions
> both ways so I am talking about both cases here, Jan's with the first
> patch and Ken's with the second patch. Please do correct me if I am
> wrong though! I will run some detailed tests tonight.

As I wrote to Ken (private e-mail), let us wait for Corinna: she knows
all the nooks and crannies here ...

As far as I can tell, path_conv::check() is invoked for posix -> win32
only; that is, in cygwin_conv_path() (winsup/cygwin/path.cc).

But, again, let us wait for Corinna.

Regards,
Henri


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Re: cygwin_conv_path sometimes removes trailing slash

[Corinna Vinschen]

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Hi Ray,

On Jan 31 22:17, Ray Donnelly wrote:
> On Sun, Jan 31, 2016 at 11:38 AM, Jan Nijtmans <jan.nijtmans@gmail.com> wrote:
> > 2016-01-30 4:21 GMT+01:00 Ken Brown:
> >> I'm using cygwin_conv_path to convert Win32 paths to POSIX paths, and I'm
> >> puzzled by the conversion
> >>
> >>   d:/ --> /cygdrive/d
> >>
> >> without the trailing slash.  By contrast, we have
> >>
> >>   d:/foo/ --> /cygdrive/d/foo/
> >
> > This came up before:
> >    <https://cygwin.com/ml/cygwin/2015-10/msg00048.html>
> > I had to workaround it in tkimg.
> >
> > It's easy to workaround in your program, but - indeed -
> > that shouldn't be necessary. I too would expect that
> > when the input contains a slash, the output should too.
> >
> 
> I've attached the patch that we use on MSYS2 for this. We found
> ourselves patching projects all over the open-source landscape
> otherwise

How many projects require exposure to the conversion from POSIX to Win32
paths?  This is something which should be used in applications only very
rarely.  Usually they just feed the POSIX path into functions like open,
etc., and that's it.

> so fixing it once and for all seems sensible. Note however,
> a full fix also requires another patch that I posted two years ago [1]
> that Corinna chose not to apply. In the two years since, we've yet to
> find any issue with that patch. I will rebase it shortly in-case
> there's any interest in reconsidering it.
> 
> [1] https://cygwin.com/ml/cygwin-patches/2014-q1/msg00010.html

Your patches don't work for Ken's case since path_conv::check is never
called for CCP_WIN_A_TO_POSIX/CCP_WIN_W_TO_POSIX conversion.  I have a
patch in the loop to fix that.

I'm not quite sure what your first patch is supposed to accomplish in
the POSIX->WIN case.  tail == path_copy + 1 means the incoming path is
"/".  Your patch will result in changing the conversion of 

  /  -->  C:\cygwin

to

  /  -->  C:\cygwin\

Is that really desired?  What especially bugs me is that this occurs in
the very core of the path conversion which isn't only used in places
exposed to user space.


Thanks,
Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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Re: cygwin_conv_path sometimes removes trailing slash

[Ray Donnelly]

On Mon, Feb 8, 2016 at 6:13 PM, Corinna Vinschen
<corinna-cygwin@cygwin.com> wrote:
> Hi Ray,
>

Hi Corinna,

Sorry for the delay, I've been snowed under with day-job things lately.

> On Jan 31 22:17, Ray Donnelly wrote:
>> On Sun, Jan 31, 2016 at 11:38 AM, Jan Nijtmans <jan.nijtmans@gmail.com> wrote:
>> > 2016-01-30 4:21 GMT+01:00 Ken Brown:
>> >> I'm using cygwin_conv_path to convert Win32 paths to POSIX paths, and I'm
>> >> puzzled by the conversion
>> >>
>> >>   d:/ --> /cygdrive/d
>> >>
>> >> without the trailing slash.  By contrast, we have
>> >>
>> >>   d:/foo/ --> /cygdrive/d/foo/
>> >
>> > This came up before:
>> >    <https://cygwin.com/ml/cygwin/2015-10/msg00048.html>
>> > I had to workaround it in tkimg.
>> >
>> > It's easy to workaround in your program, but - indeed -
>> > that shouldn't be necessary. I too would expect that
>> > when the input contains a slash, the output should too.
>> >
>>
>> I've attached the patch that we use on MSYS2 for this. We found
>> ourselves patching projects all over the open-source landscape
>> otherwise
>
> How many projects require exposure to the conversion from POSIX to Win32
> paths?  This is something which should be used in applications only very
> rarely.  Usually they just feed the POSIX path into functions like open,
> etc., and that's it.
>
>> so fixing it once and for all seems sensible. Note however,
>> a full fix also requires another patch that I posted two years ago [1]
>> that Corinna chose not to apply. In the two years since, we've yet to
>> find any issue with that patch. I will rebase it shortly in-case
>> there's any interest in reconsidering it.
>>
>> [1] https://cygwin.com/ml/cygwin-patches/2014-q1/msg00010.html
>
> Your patches don't work for Ken's case since path_conv::check is never
> called for CCP_WIN_A_TO_POSIX/CCP_WIN_W_TO_POSIX conversion.  I have a
> patch in the loop to fix that.

Great!

>
> I'm not quite sure what your first patch is supposed to accomplish in
> the POSIX->WIN case.  tail == path_copy + 1 means the incoming path is
> "/".  Your patch will result in changing the conversion of
>
>   /  -->  C:\cygwin
>
> to
>
>   /  -->  C:\cygwin\
>
> Is that really desired?  What especially bugs me is that this occurs in
> the very core of the path conversion which isn't only used in places
> exposed to user space.

It is what we needed on MSYS2. When building a "native" GCC, we'd pass
e.g. --sysroot=/ and that'd get expanded to "C:/cygwin" and have say a
sys include dir of "sys/include" appended making
C:/cygwinsys/include". I can't guarantee that *nothing* else will
break because of this change except to offer that anecdotally no msys2
package (i.e. those packages in MSYS2 that are purely POSIX) build or
execution failure was ever determined to be caused by making this
change.

Best regards,

Ray.

>
>
> Thanks,
> Corinna
>
> --
> Corinna Vinschen                  Please, send mails regarding Cygwin to
> Cygwin Maintainer                 cygwin AT cygwin DOT com
> Red Hat

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Re: cygwin_conv_path sometimes removes trailing slash

[Ken Brown]

On 1/29/2016 10:21 PM, Ken Brown wrote:
> I'm using cygwin_conv_path to convert Win32 paths to POSIX paths, and
> I'm puzzled by the conversion
>
>    d:/ --> /cygdrive/d
>
> without the trailing slash.

Hi Corinna,

After your recent patch (git commit 8b83da2), I now see the conversion

   d:/ --> /cygdrive/d/

as expected.  But I have

   C: /c some_fs binary,posix=0 0 0

in my /etc/fstab, and I get the conversion

   C:/ --> /c

I would expect conversion to preserve the trailing slash here too.

Ken

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Re: cygwin_conv_path sometimes removes trailing slash

[Corinna Vinschen]

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Hi Ken,

On Feb 14 14:08, Ken Brown wrote:
> On 1/29/2016 10:21 PM, Ken Brown wrote:
> >I'm using cygwin_conv_path to convert Win32 paths to POSIX paths, and
> >I'm puzzled by the conversion
> >
> >   d:/ --> /cygdrive/d
> >
> >without the trailing slash.
> 
> Hi Corinna,
> 
> After your recent patch (git commit 8b83da2), I now see the conversion
> 
>   d:/ --> /cygdrive/d/
> 
> as expected.  But I have
> 
>   C: /c some_fs binary,posix=0 0 0
> 
> in my /etc/fstab, and I get the conversion
> 
>   C:/ --> /c
> 
> I would expect conversion to preserve the trailing slash here too.

Right.  You're hitting a border case there.  I fixed in in the repo.


Thanks,
Corinna

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Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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