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

[Eli Zaretskii <eliz@gnu.org>]

> From: Guy Offer <guyof@checkpoint.com>
> CC: "51894@debbugs.gnu.org" <51894@debbugs.gnu.org>
> Date: Thu, 18 Nov 2021 07:53:37 +0000
> 
> * 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. 

Why is "set substitute-path" command needed?  The program you are
debugging should have the source location recorded in the debug info,
so that step should not be needed.

I'm asking because perhaps this step is an important part of the
problem.

Also, can you try "M-x gud-gdb RET" instead, and see if the problem
exists there as well?  Maybe there's something in gdb-mi.el that
doesn't work well in this case, in particular when it parses the file
names reported by GDB's MI interface.  For that reason, I'd be
interested to see the raw data about source file names emitted by GDB
in response to Emacs's queries.  For that purpose, activate the
gdb-enable-debug minor mode, and show the contents of the variable
gdb-debug-log after a command that results in such failures.

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

I believe that was fixed in Emacs 28.