Philipp Stephani <p.stephani2@gmail.com> writes:

Hi Philipp,

> Sorry for being imprecise. Yes, I mean quoted filenames. (It's
> possible that the issue also arises for true remote filenames, but I
> haven't checked.)

"True remote filename" is still a wrong phrase. Quoted file names and
remote file names play different games.

> You can easily reproduce user-facing problems. Assuming you have some
> binary installed that would check Java files using the legacy backend:
>
> $ touch /tmp/{a,b}.java
> $ emacs -Q -eval '(progn (add-hook (quote prog-mode-hook) (quote
> flymake-mode)) (ediff "/:/tmp/a.java" "/:/tmp/b.java"))'
>
> And Emacs immediately hangs because it runs into the endless loop.
> Stacktrace in this case is
>
> Debugger entered--Lisp error: (quit)
>   display-warning((flymake flymake-proc) "Failed to delete dir /,
> error ignored" :error "*Flymake log*")
>   flymake--log-1(1 flymake-proc "Failed to delete dir %s, error
> ignored" "/")
>   flymake-proc--safe-delete-directory("/")
>   flymake-proc--delete-temp-directory("/tmp/:/tmp/")
>   flymake-proc-simple-java-cleanup()
>   #f(compiled-function () #<bytecode 0x11a4ea9>)()
>   flymake-proc-legacy-flymake(#f(compiled-function (&rest args)
> #<bytecode 0x11a4e51>))
>   flymake--run-backend(flymake-proc-legacy-flymake)
>   #f(compiled-function (backend) #<bytecode 0x117b195>)
> (flymake-proc-legacy-flymake)
>   run-hook-wrapped(#f(compiled-function (backend) #<bytecode
> 0x117b195>) flymake-proc-legacy-flymake)
>   flymake-start((post-command) nil)
>   #f(compiled-function () #<bytecode 0x1180771>)()
>   set-window-buffer(nil #<buffer a.java>)
>   switch-to-buffer(#<buffer a.java>)
>   ediff-setup-windows-multiframe-compare(#<buffer a.java> #<buffer
> b.java> nil #<buffer *Ediff Control Panel*>)
>   ediff-setup-windows-multiframe(#<buffer a.java> #<buffer b.java> nil
> #<buffer *Ediff Control Panel*>)
>   ediff-setup-windows-default(#<buffer a.java> #<buffer b.java> nil
> #<buffer *Ediff Control Panel*>)
>   ediff-setup-windows(#<buffer a.java> #<buffer b.java> nil #<buffer
> *Ediff Control Panel*>)
>   ediff-setup(#<buffer a.java> "/:/tmp/a.java" #<buffer b.java>
> "/:/tmp/b.java" nil nil nil ((ediff-job-name . ediff-files)) nil)
>   ediff-files-internal("/:/tmp/a.java" "/:/tmp/b.java" nil nil
> ediff-files)
>   ediff("/:/tmp/a.java" "/:/tmp/b.java")
>   (progn (add-hook (quote prog-mode-hook) (quote flymake-mode)) (ediff
> "/:/tmp/a.java" "/:/tmp/b.java"))
>   eval((progn (add-hook (quote prog-mode-hook) (quote flymake-mode))
> (ediff "/:/tmp/a.java" "/:/tmp/b.java")))
>   command-line-1(("-f" "toggle-debug-on-quit" "-eval" "(progn
> (add-hook (quote prog-mode-hook) (quote flymake-mode)) (ediff
> \"/:/tmp/a.java\" \"/:/tmp/b.java\"))"))
>   command-line()
>   normal-top-level()

The following patch fixes this problem: