bug#8954: 23.3.50; flymake handles read-only directories badly

[Stefan Monnier]

> If I open a system include file, and have flymake-mode in my
> c-mode-hook, I get:

> Note: file is write protected
> flymake-save-buffer-in-file: Opening output file: permission denied, 
> /usr/include/regex_flymake.h

> and (the actual bug) the buffer displayed is not regex.h

I've installed the patch below which should fix the worst part of
this bug.


        Stefan


=== modified file 'lisp/ChangeLog'
--- lisp/ChangeLog      2012-04-10 23:34:25 +0000
+++ lisp/ChangeLog      2012-04-11 00:20:36 +0000
@@ -1,3 +1,7 @@
+2012-04-11  Stefan Monnier  <monnier@iro.umontreal.ca>
+
+       * progmodes/flymake.el (flymake-mode): Beware read-only dirs (bug#8954).
+
 2012-04-10  Sébastien Gross  <seb@chezwam.org>  (tiny change)
 
        * progmodes/hideshow.el (hs-hide-all): Don't infloop on comments

=== modified file 'lisp/progmodes/flymake.el'
--- lisp/progmodes/flymake.el   2012-02-08 02:12:24 +0000
+++ lisp/progmodes/flymake.el   2012-04-10 23:06:08 +0000
@@ -1356,8 +1356,12 @@
       (setq flymake-timer
             (run-at-time nil 1 'flymake-on-timer-event (current-buffer)))
 
-      (when flymake-start-syntax-check-on-find-file
-        (flymake-start-syntax-check)))))
+      (when (and flymake-start-syntax-check-on-find-file
+                 ;; Since we write temp files in current dir, there's no point
+                 ;; trying if the directory is read-only (bug#8954).
+                 (file-writable-p (file-name-directory buffer-file-name)))
+        (with-demoted-errors
+          (flymake-start-syntax-check))))))
 
    ;; Turning the mode OFF.
    (t