bug#33524: 27.0.50; Suspicious code in flymake-proc around temporary directories

[Philipp Stephani]

Am Mi., 28. Nov. 2018 um 09:58 Uhr schrieb Michael Albinus <michael.albinus@gmx.de>:

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

Hi Phillipp,

> I've noticed that the temporary directory code in flymake-proc has
> issues with remote filenames.  For example:
>
> $ emacs -Q -batch -l flymake-proc --eval='(print (flymake-proc-create-temp-with-folder-structure "/:/dir" nil))'
>
> "/tmp/:/dir"
>
> Clearly that's not what was intended.  Rather, this should create the
> directory structure on the remote machine.

I don't understand. "/:/dir" is not a remote file name, it is a quoted
file name. See (info "(emacs) Quoted File Names") for a description.

Could you pls explain what you want to achieve? This would help to
understand your problem.

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.)

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()