bug#52488: Try basename of agrv0's realpath for .pdmp lookup in libexecdir

[Ken Brown <kbrown@cornell.edu>]

On 12/14/2021 2:32 PM, Ken Brown wrote:
> On 12/14/2021 2:01 PM, Bhavin Gandhi wrote:
>> As the comment from load_pdump_find_executable explains, there are
>> setups where the /usr/bin/emacs is a symlink managed by something like
>> alternatives. This symlink eventually points to an Emacs binary like
>> emacs-28.0.90. These kind of setups are used to have installation of
>> multiple versions of Emacs on the same system.
> 
> This is exactly the setup that I use on Cygwin, as I alluded to in my message to 
> the other bug report.  But I didn't mention there that I use symlinks managed by 
> alternatives.
> 
>> Supporting resolution of these symlinks while searching for a .pdmp file
>> will make it possible to put the .pdmp files in libexecdir instead of
>> putting those in the /usr/bin/. I think this should be in addition to
>> the possibilities tried currently.
> 
> Yes.  It's precisely because the symlinks aren't resolved that I've been putting 
> the .pdmp files in /usr/bin, alongside the emacs executables.

On further reflection, I don't think the problem is symlink resolution for the 
.pdmp file.  I think the problem is that load_pdmp doesn't look in libexecdir 
for a .pdmp file whose name matches the name of the emacs executable.  For 
example, suppose I have a symlink /usr/bin/emacs that resolves to 
/usr/bin/emacs-nox.exe.  Then load_pdmp looks for /usr/bin/emacs-nox.pdmp, but 
it doesn't look for /usr/libexec/emacs/28.0.90/x86_64-pc-cygwin/emacs-nox.pdmp. 
  I'm working on a patch to fix this.

Ken