How to let Emacs c-mode understand Chromium specific macro like EXPORT?

[Dean Liao]

Hi all,

I'm a new developer for Chromium codebase. I have set my Emacs to use google-set-c-style , but it doesn't recognize Chromium macro like EXPORT.  So it makes the wrong indentation for header file with class definition with EXPORT macro after class name.

Does anyone have receipt of this issue? I didn't find a document mention about it. Thanks.

Best,

Dean

[Sylvain Defresne]

I do not use emacs myself, but at https://chromium.googlesource.com/chromium/src/+/master/docs/emacs.md there is documentation on how to set up emacs to use TAB to format current bloc with clang-format. Could this work for you?

-- Sylvain

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[Yuta Kitamura]

I managed to get this working for me, but unfortunately that was not easy. Essentially, you need to edit the source code of cc-mode and recompile.

If you want to give it a try, do the following:

1. Get the latest tarball of cc-mode and expand it.
2. Run the following shell command (obviously you can change the list of EXPORTs):
   
   $ patch -p0 -u <<'__EOF__'
   --- cc-langs.el.orig 2018-02-27 16:59:23.978931404 +0900
   +++ cc-langs.el 2018-02-27 17:02:05.409110857 +0900
   @@ -2103,7 +2103,13 @@
      (c c++) '(;; GCC extension.
       "__attribute__"
         ;; MSVC extension.
   -     "__declspec"))
   +     "__declspec"
   +     ;; Custom Chromium/Blink specific keywords.
   +     "BASE_EXPORT"
   +     "CORE_EXPORT" "CONTROLLER_EXPORT" "MODULES_EXPORT"
   +     "PLATFORM_EXPORT" "BLINK_COMMON_EXPORT" "BLINK_EXPORT"
   +     "BLINK_PLATFORM_EXPORT" "WTF_EXPORT"
   +           "BASE_EXPORT" "CONTENT_EXPORT"))
    
    (c-lang-defconst c-decl-hangon-key
      ;; Adorned regexp matching `c-decl-hangon-kwds'.
   __EOF__


3. Byte-compile the source code as instructed in README.
4. In your emacs initialization file (typically ~/.emacs), add the following to prepend your modified cc-mode to load-path:
   
   (add-to-list 'load-path "~/path/to/your/cc-mode")
   
   
5. Restart emacs, and open some source code to see if XXX_EXPORT is highlighted differently, and cc-mode doesn't mis-indent within a class.
   (Alternatively, you can check the version of cc-mode by typing M-x c-version)

YMMV, but hope this helps.

Thanks,

Yuta

--

[Dean Liao]

Thank you Yuta. I saw your internal Site mentioned about this. I tried but it compiled with warning and my emacs failed to identify those EXPORT macros. It said "cc-defs.el:62:1:Warning: cl package required at runtime". Did you encounter this before?

Best,

Dean

~/.emacs.d/cc-mode-5.33 $ emacs -batch -no-site-file -q -f batch-byte-compile cc-*.el

In toplevel form:

cc-defs.el:62:1:Warning: cl package required at runtime

cc-defs.el:1036:22:Warning: Use ‘with-current-buffer’ rather than

    save-excursion+set-buffer

cc-defs.el:1915:20:Warning: Use ‘with-current-buffer’ rather than

    save-excursion+set-buffer

cc-defs.el:1935:26:Warning: Use ‘with-current-buffer’ rather than

    save-excursion+set-buffer

In c-lang-defconst:

cc-defs.el:2208:50:Warning: ‘cl-macroexpand-all’ is an obsolete function (as

    of 24.3); use ‘macroexpand-all’ instead.

In toplevel form:

cc-fix.el:49:1:Warning: assignment to free variable ‘cc-bytecomp-set-vars’

In toplevel form:

cc-fonts.el:147:16:Warning: ‘font-lock-reference-face’ is an obsolete variable

    (as of 20.3); use ‘font-lock-constant-face’ instead.

In toplevel form:

cc-langs.el:132:1:Warning: cl package required at runtime

In c-make-init-lang-vars-fun:

cc-langs.el:3492:40:Warning: ‘cl-macroexpand-all’ is an obsolete function (as

    of 24.3); use ‘macroexpand-all’ instead.

In end of data:

cc-mode.el:2123:1:Warning: the function ‘make-local-hook’ is not known to be

    defined.

In c-make-styles-buffer-local:

cc-styles.el:655:30:Warning: ‘make-variable-buffer-local’ not called at

    toplevel

In end of data:

cc-styles.el:678:1:Warning: the function ‘c-guess-basic-syntax’ might not be

    defined at runtime.

cc-styles.el:678:1:Warning: the function ‘make-local-hook’ is not known to be

    defined.

In toplevel form:

cc-subword.el:164:5:Warning: ‘make-variable-buffer-local’ not called at

    toplevel

[Dean Liao]

Sylvain, thank you for your tips. 
https://chromium.googlesource.com/chromium/src/+/master/docs/emacs.md#use-google_s-c_style works.

[Yuta Kitamura]

I also saw bite-compiling generated a lot of warnings, but it worked anyway. Seems like those warnings are normal for cc-mode.

To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/chromium-dev/b14052ee-8d1e-4de4-aaa2-aefa2b6fc0af%40chromium.org.