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I'm using native windows emacs together with mingw. When there's a compile error, the *compilation* buffer looks like this:

make -C ..
make: Entering directory `/c/Users/m.grunwald/Documents/Projects/aaaa/bbbb/cccc/dddd'
compiling Update.c
../Source/Update.c: In function 'SetMessage':
../Source/Update.c:52:1: error: 'd' undeclared (first use in this     function)
 d

When I use (next-error), emacs prompts me to "Find this error in...:" and the path it suggests is

c:/c/Users/m.grunwald/Documents/Projects/aaaa/bbbb/cccc/dddd/

Now this is neither a valid windows nor a valid mingw path and it makes compiling tideous. How do I get rid of the leading "C:" ?

Please note that the path that "make" prompts in the 2nd line is correct.

The linked topic "C:/c/user/...my-folder/ isn't an existing directory" error is about the same problem, but fixes it only in magit. I have no idea where I should tackle the problem for compile-mode and this is the wrong aproach, IMHO. It should be possible to fix this in emacs itself and only once, not once in each mode...

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    Related: emacs.stackexchange.com/questions/12593/…, not sure offhand how to fix it for compilation mode though.
    – npostavs
    Commented Jan 14, 2016 at 15:22
  • I strongly suggest that you do not mix native Windows Emacs with POSIX-y tools.
    – nanny
    Commented Jan 14, 2016 at 17:15
  • @nanny: Difficult. Emacs on cygwin works well, but is slow as molassis compared to the native one. I don't want to give up this speed!
    – Markus
    Commented Jan 22, 2016 at 12:15
  • @Markus In my opinion, it's definitely worth it to use Cygwin. Another alternative is to use an X server on Windows (e.g. VcXsrv) with Putty, and forward Emacs from a gnu/linux server.
    – nanny
    Commented Jan 22, 2016 at 14:17
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    maybe cygwin-mount.el would help? gnu.org/software/emacs/manual/html_node/efaq-w32/…
    – npostavs
    Commented Jan 22, 2016 at 14:53

1 Answer 1

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It looks like cygwin-mount.el only works for cygwin names. Emacs already comes with unmsys--file-name to convert msys names, so I used it to write an msys file name handler for expand-file-name and substitute-in-file-name (it's unclear to me how to know which operations are important, so I just followed cygwin-mount.el's lead. The code below seems to work for me).

(defun msys-file-name-handler (operation &rest args)
  "Call `unmsys--file-name' on file names."
  (let ((inhibit-file-name-handlers
         (cons 'msys-file-name-handler
               (and (eq inhibit-file-name-operation operation)
                    inhibit-file-name-handlers)))
        (inhibit-file-name-operation operation))
    (pcase (cons operation args)
      (`(expand-file-name ,name . ,(or `(,directory) directory))
       (expand-file-name (unmsys--file-name name) (if directory (unmsys--file-name directory))))
      (`(substitute-in-file-name ,name)
       (substitute-in-file-name (unmsys--file-name name)))
      (_ (apply operation args)))))

(add-to-list 'file-name-handler-alist '("\\`/[a-zA-Z]/" . msys-file-name-handler))

;; Work around apparent bug in `compilation-parse-errors'.
(defun save-match-data-advice (fun &rest args)
  "Add this as `:around' advice to save the match-data."
  (save-match-data
    (apply fun args)))

(advice-add 'compilation-error-properties :around #'save-match-data-advice)
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  • Unfortunately it breaks next-error and previous-error, if I include your code...
    – Markus
    Commented Feb 24, 2017 at 9:13
  • @Markus Oh, I had only tried applying the code after running M-x compile, it does indeed break subsequent compiles. It looks like a bug in the Emacs code that doesn't save match data; I've now added some advising code to the answer to work around it.
    – npostavs
    Commented Feb 24, 2017 at 19:09
  • You, sir npostavs are my saviour! Since 1½ years I had to manually workaround this and now it works... thank you so much!
    – Markus
    Commented Feb 27, 2017 at 6:04

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