U.11.4 Other Commands for C Mode

C-M-h

Put mark at the end of a function definition, and put point at the beginning (c-mark-function).

M-q

Fill a paragraph, handling C and C++ comments (c-fill-paragraph). If any part of the current line is a comment or within a comment, this command fills the comment or the paragraph of it that point is in, preserving the comment indentation and comment delimiters.

C-c C-e

Run the C preprocessor on the text in the region, and show the result, which includes the expansion of all the macro calls (c-macro-expand). The buffer text before the region is also included in preprocessing, for the sake of macros defined there, but the output from this part isn't shown.

When you are debugging C code that uses macros, sometimes it is hard to figure out precisely how the macros expand. With this command, you don't have to figure it out; you can see the expansions.

C-c C-\

Insert or align `\' characters at the ends of the lines of the region (c-backslash-region). This is useful after writing or editing a C macro definition.

If a line already ends in `\', this command adjusts the amount of whitespace before it. Otherwise, it inserts a new `\'. However, the last line in the region is treated specially; no `\' is inserted on that line, and any `\' there is deleted.

M-x cpp-highlight-buffer

Highlight parts of the text according to its preprocessor conditionals. This command displays another buffer named `*CPP Edit*', which serves as a graphic menu for selecting how to display particular kinds of conditionals and their contents. After changing various settings, click on `[A]pply these settings' (or go to that buffer and type a) to rehighlight the C mode buffer accordingly.

C-c C-s

Display the syntactic information about the current source line (c-show-syntactic-information). This is the information that directs how the line is indented.

M-x cwarn-mode

M-x global-cwarn-mode

CWarn minor mode highlights certain suspicious C and C++ constructions:

• Assignments inside expressions.
• Semicolon following immediately after `if', `for', and `while' (except after a `do ... while' statement);
• C++ functions with reference parameters.

You can enable the mode for one buffer with the command M-x cwarn-mode, or for all suitable buffers with the command M-x global-cwarn-mode or by customizing the variable global-cwarn-mode. You must also enable Font Lock mode to make it work.

M-x hide-ifdef-mode

Hide-ifdef minor mode hides selected code within `#if' and `#ifdef' preprocessor blocks. See the documentation string of hide-ifdef-mode for more information.

M-x ff-find-related-file

Find a file "related" in a special way to the file visited by the current buffer. Typically this will be the header file corresponding to a C/C++ source file, or vice versa. The variable ff-related-file-alist specifies how to compute related file names.