How to use C++ comments "//" in c-mode?

Question

In c-mode comment-region is adding /* */ style comments.

Is there a way to default to using C++ style // prefix in C source files instead?

ideasman42 · Answer 1 · 2017-08-28T04:32:23.953

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This can be done by changing comment-start & comment-end.

(add-hook 'c-mode-hook (lambda () (setq comment-start "//"
                                        comment-end   "")))

Found the answer after further searching here

edited Aug 28 '17 at 04:32

answered Aug 17 '17 at 06:31

ideasman42

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You may also be interested in `comment-start-skip` for certain use cases within `c-mode`. – lawlist Aug 17 '17 at 16:12

score 2 · Accepted Answer · edited Sep 01 '17 at 10:31

2

Support for toggling between block-style and line-style comments was added a few months ago, and should be included in the next release.

If you have a snapshot of the development version of emacs (from master after June 15, 2017), you can use (c-toggle-comment-style) to toggle the comment style.

See http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=7a2038d7c887e4fa08a91950a7494d1dd20c39e1

And the related conversation on emacs-devel: http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=7a2038d7c887e4fa08a91950a7494d1dd20c39e1

EDIT:

To enable them by default:

(add-hook 'c-mode-hook (lambda () (c-toggle-comment-style -1)))

edited Sep 01 '17 at 10:31

T. Verron

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answered Aug 30 '17 at 09:27

Toon Claes

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Is there a way to set the default? - so toggling each time isn't needed. – ideasman42 Aug 30 '17 at 10:35
You still need a hook I think. See updated answer. – Toon Claes Sep 01 '17 at 09:21

How to use C++ comments "//" in c-mode?

2 Answers2