Learning GNU Emacs, Second Edition

C and C++ Modes

Emacs automatically enters C mode when you visit a file whose suffix is .c, .h, .y (for yacc grammars), or .lex (lex specification files). Emacs invokes C++ mode when you visit a file whose suffix is .C, .H, .cc, .hh, .cpp, .cxx, .hxx, .c++, or .h++. You can also put any file in C mode manually by typing ESC x c-mode RETURN. Similarly, you can use c++-mode to put a buffer into C++ mode.

Both C and C++ modes are implemented in the same Emacs LISP package, called cc-mode, which also includes a mode for the Objective-C language used in NextStep environments. C mode understands both ANSI C and the older Kernighan and Ritchie C syntax. We describe C mode functions, but you should assume that everything also applies to C++ mode. C++ mode has a small number of additional features, which we’ll describe at the end of this section.

We should also note that Emacs’ mode for Perl, the language gaining wide popularity because of its use in World Wide Web server programming, is derived from an older version of C mode. If you program in Perl, you will find that virtually all of the motion, indentation, and formatting commands in C mode apply equally to Perl mode, with perl- replacing c- in their names. Emacs invokes Perl mode on files with suffix .pl.

In C mode, Emacs understands the syntax elements described earlier in this chapter. The characters semicolon (;), colon (:), comma (,) curly braces ({ and }), and pound sign (#, for C preprocessor commands) are all electric, ...