bug#19466: 25.0.50; xref-find-def doesn't find C functions

[martin rudalics]

> The alternative implementation was pushed to scratch/xref, and it's waiting 
for Martin's comments (bug#19468).

Sorry, I didn't have time yet to give it a through testing.  Anyway,
Eli's concern

  "... if I switch to the window where that candidate is displayed, the
   window switches buffers on me ..."

is IMHO more serious than your

  "I want the user to be able to easily return to the window
   configuration that was before xref-find-definitions was called."

so I think you should push the `quit-window' based solution to trunk
(which, from the few testing I gave it, seems to handle this case well).


One thing that has annoyed me ever since is the buffers that pile up
while browsing tags.  I always dreamt of a good heuristic to get rid of
them.  Maybe you could try making provisions like

(1) this buffer is killable because it has been probably visited
    exclusively by and only accidentally during xrefing, and

(2) have the command that quits the *xref* buffer optionally kill the
    buffers marked in (1).

A heuristic for (1) could go as follows:

  The buffer was created during xrefing, the window was never selected
  while it showed that buffer and either its buffer was "immediately"
  replaced by another xrefed one or `xref--quit' was invoked.


You might also consider setting `other-window-scroll-buffer' to the
window used by `xref-show-location-at-point'.

martin, who'd prefer (user-error "No reference at point")