bug#51894: 27.2; GDB Gud support on Cygwin has trouble accessing shared files on Windows network drives.

[Guy Offer]

Hi, 

Steps to set up this configuration:

Background: 
When working on gdb from Emacs you can see the source code from 2 Emacs 
windows/buffers:
- the gdb command window: the gdb prompt that displays the current source code 
line.
- the primary source window: an Emacs window that automatically opened and 
displays the source file with an arrow pointing on the current line being 
processed.
The problem is that when the source code is on network drive mounted through 
Windows 10 drives (F:, G:, etc.) it will not be available to one of these 
windows. 

Working machine : Windows 10

* Have the source pointed by a network drive (e.g. F:/source, etc.).
* Install Cygwin on the local machine: (including make, X11, GNU Emacs 27.2, 
gcc, packages etc.). 
* Download and compile gdb 11.1 (I had to compile myself to work with linux 
target and build x86_64-redhat-linux-gnu-gdb).
* Activate gdb from emacs by : Alt-x, gdb, gdb -i=mi etc.

Now you see the problems:
* If you set the code path (set substitute-path) to the actual code location 
/cygdrive/f/source the code will be available to the gdb command window but 
will not be opened automatically in the primary source window/buffer. 
* If you set the code location to //cygdrive/f/source the code will be 
available to the source window - but not to the gdb command window. 

Possible solution - mounting the source code through Cygwin /mnt. 

Another problem : when the source is not available the Emacs command prompt get 
into a loop.

Thanks,
Guy


-----Original Message-----
From: Ken Brown [mailto:kbrown@cornell.edu] 
Sent: Wednesday, 17 November 2021 19:41
To: Eli Zaretskii <eliz@gnu.org>; Guy Offer <guyof@checkpoint.com>
Cc: 51894@debbugs.gnu.org
Subject: Re: bug#51894: 27.2; GDB Gud support on Cygwin has trouble accessing 
shared files on Windows network drives.

On 11/17/2021 12:03 PM, Eli Zaretskii wrote:
>> From: Guy Offer <guyof@checkpoint.com>
>> CC: "51894@debbugs.gnu.org" <51894@debbugs.gnu.org>
>> Date: Wed, 17 Nov 2021 15:01:09 +0000 Pls note that this happens only 
>> if f is a network drive .
> 
> So maybe it's a Cygwin-specific problem with networked drives?  I'll 
> CC Ken Brown, who is our Cygwin specialist.  Ken, does this ring a 
> bell? does /cygdrive/x/ fail when X is a networked drive?

I'm not aware of any such problem.  I never use networked drives myself, but if 
Guy can tell me exactly how he created his, I'll see if I can reproduce the 
problem.

Ken


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