Flymake mode is a minor mode that performs on-the-fly syntax
checking for many programming and markup languages, including C, C++,
Perl, HTML, and TeX/LaTeX. It is somewhat analogous to Flyspell
mode, which performs spell checking for ordinary human languages in a
similar fashion (see Checking and Correcting Spelling). As you edit a file, Flymake mode
runs an appropriate syntax checking tool in the background, using a
temporary copy of the buffer. It then parses the error and warning
messages, and highlights the erroneous lines in the buffer. The
syntax checking tool used depends on the language; for example, for
C/C++ files this is usually the C compiler. Flymake can also use
build tools such as
make for checking complicated projects.
To enable Flymake mode, type M-x flymake-mode. You can jump to the errors that it finds by using M-x flymake-goto-next-error and M-x flymake-goto-prev-error. To display a detailed overview of the diagnostics for the current buffer, use the command M-x flymake-show-buffer-diagnostics; to display a similar overview of diagnostics for the entire project (see Working with Projects), use M-x flymake-show-project-diagnostics.
For more details about using Flymake, see Flymake in The Flymake Manual.