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bug#37862: [PATCH] Use alternative C++ source files for determining C/C+
From: |
Alan Mackenzie |
Subject: |
bug#37862: [PATCH] Use alternative C++ source files for determining C/C++ header files. |
Date: |
Sun, 27 Oct 2019 13:30:38 +0000 |
User-agent: |
Mutt/1.10.1 (2018-07-13) |
Hello, Hong.
On Mon, Oct 21, 2019 at 20:12:51 -0700, Hong Xu wrote:
> * lisp/progmodes/cc-mode.el (c-or-c++-mode): Add check for the
> existence of alternative C++ source files.
> ---
> lisp/progmodes/cc-mode.el | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
> diff --git a/lisp/progmodes/cc-mode.el b/lisp/progmodes/cc-mode.el
> index 6bdfb170f1ba..940bd4be3f92 100644
> --- a/lisp/progmodes/cc-mode.el
> +++ b/lisp/progmodes/cc-mode.el
> @@ -2492,16 +2492,23 @@ c-or-c++-mode
> matching on file name insufficient for detecting major mode that
> should be used.
> -This function attempts to use file contents to determine whether
> -the code is C or C++ and based on that chooses whether to enable
> -`c-mode' or `c++-mode'."
> - (if (save-excursion
> +This function attempts to use file contents and the existence of
> +alternative C++ source files to determine whether the code is C
> +or C++ and based on that chooses whether to enable `c-mode' or
> +`c++-mode'."
> + (if (or
> + (save-excursion
> (save-restriction
> (save-match-data
> (widen)
> (goto-char (point-min))
> (re-search-forward c-or-c++-mode--regexp
> (+ (point) c-guess-region-max) t))))
> + ;; We could have gone through auto-mode-alist here, but it
> + ;; might be too slow.
> + (let ((base-name (file-name-sans-extension (buffer-file-name))))
> + (seq-find (lambda (ext) (file-exists-p (concat base-name ext)))
> + '(".cc" ".cpp" ".cxx" ".c++"))))
> (c++-mode)
> (c-mode)))
> --
> 2.20.1
Thanks for writing this proposal.
I think it would be better, given a foo.h, to find all files foo.*, and
test each one in turn for a match in auto-mode-alist. Searching this
alist is really not that slow, particularly as it is only being done a
few times, and not in a tight loop.
For this, we really want a function in the Emacs core which would find
the match in auto-mode-alist. Currently, this functionality is open
coded in set-auto-mode (in .../lisp/files.el).
However, I'm a bit sceptical about the use of this proposed facility.
Many projects (possibly most) have .c/.c++ files in a directory called
"src", and .h files in a separate directory called "include". This
proposed facility wouldn't work in such a set up. To extend it to cope
with separate "src"/"include" directories would make it messy.
--
Alan Mackenzie (Nuremberg, Germany).