ll-debug.el provides commands to support a low level debug style. It features quick insertion of various debug output statements and improved functions for commenting and uncommenting chunks of code. I don't use debuggers very much. I know they can be a big help in some situations and I tried some of them, but I find it almost always more direct/convenient/enlightening to put a quick 'printf' into a critical area to see what is happening than to fire up a big clumsy extra program where it takes me ages just to step through to the interesting point. In order to avoid repeated typing of 'printf("I AM HERE\n");' and similar stuff, I created `ll-debug-insert'. It inserts a statement into your sourcecode that will display a debug message. It generates unique messages on each invocation (the message consists of a big fat DEBUG together with a counter and the current filename). See variable `ll-debug-statement-alist' if you want to know which modes are currently supported by ll-debug. You can add new modes with `ll-debug-register-mode'. When I have found the buggy spot, I like to keep a version of the old code in place, just in case I mess things up. `ll-debug-copy-and-comment-region-or-line' helps here, it makes a copy of the current line (or the current region, if active) and comments out the original version. I always missed a keystroke that toggles the 'comment state' of a line (or region) of sourcecode. I need to turn a line or a block of code on and off quickly. `ll-debug-toggle-comment-region-or-line' does just that. Finally, if you want to spit out the values of a lot of variables you can use `ll-debug-insert' with a C-u prefix arg. It calls mode-specific skeletons that keep asking for variable names (and sometimes format specifiers) in the minibuffer. If you just press return here the skeleton interaction ends and a statement to print the names and the values of the variables is inserted in the buffer. If you want to get rid of the debug messages, use `ll-debug-revert'. It finds and removes the lines with the debug output statements, asking for confirmation before it removes anything. Prerequisites: I made the latest version of ll-debug with GNU Emacs 26.3. Please let me know if other versions work. Installation: Get the newest version of ll-debug.el via https://github.com/replrep/ll-debug or http://www.cbrunzema.de/software.html#ll-debug and put it in your load-path. Add the following form to your init file (~/.emacs or ~/.emacs.d/init.el): (require 'll-debug) Now you can bind ll-debug commands to keystrokes yourself or just call `ll-debug-mode'. `ll-debug-mode' is a minor mode that installs `ll-debug-mode-map'. It clobbers C-v, which may not be completely emacs-political-correct, but it happens to be the stuff I use daily, it is only a suggestion, blah, if you don't like it, don't use it blah blah, do it your own way blah bla blah and don't flame me.... `ll-debug-mode-map' has the following keybindings: C-v C-v `ll-debug-toggle-comment-region-or-line' C-v v `ll-debug-uncomment-region-or-line' C-v C-y `ll-debug-copy-and-comment-region-or-line' C-v C-d `ll-debug-insert' If you want to activate `ll-debug-mode' automatically for certain modes, put it into the usual hooks, e.g. (add-hook 'cperl-mode-hook #'ll-debug-mode) Usage example 1: If you activate `ll-debug-mode', hitting C-v C-d in a c-mode buffer called 'main.c' produces: printf("DEBUG-1-main.c\n"); a second C-v C-d prints printf("DEBUG-2-main.c\n"); and so on. The following conversation uses the variable output (the part in '[' and ']' takes place in the minibuffer): C-u C-v C-d [ foo s bar d baz f ] This gives: printf("DEBUG-3-main.c foo:%s bar:%d baz:%f\n", foo, bar, baz); Usage example 2: In a lisp-mode buffer called 'tree.lisp' this: C-v C-d C-v C-d C-u C-v C-d [ foo bar baz ] produces the following lines: (CL:format t "DEBUG-1-tree.lisp~%") (CL:format t "DEBUG-2-tree.lisp~%") (CL:format t "DEBUG-3-tree.lisp foo:~S bar:~S baz:~S~%" foo bar baz) Usage example 3: The keybindings in `ll-debug-mode-map' will call a alternative versions for variable output if one ore more C-u prefix args are given. An alternative version is currently available in (c)perl-mode only. So, in a (c)perl-mode buffer called 'answer.pl' these keys C-u C-u C-v C-d [ @quux %thud $grunt ] produce: print "DEBUG-1-answer.pl ", Data::Dumper->Dump([\@quux, \%thud, $grunt], [qw/*quux *thud grunt/]), "\n"; Customisation: You can use a different string for the debug messages by setting the variable `ll-debug-output-prefix'. If you set it e.g. to "# DEBUG-" your debug output won't disturb gnuplot datafiles anymore. If you don't like c++'s streams, you can request the printf style output by putting the following in your init file: (setcdr (assq 'c++-mode ll-debug-statement-alist) (cdr (assq 'c-mode ll-debug-statement-alist))) If you want to have dynamic output not only according to the major mode, you can substitute functions in `ll-debug-statement-alist'. For example, the following snippet uses prefix 'printk' instead of 'printf' if you are editing c-sources in a file on a path containing a 'linux' component: (setf (ll-debug-struct-prefix (cdr (assq 'c-mode ll-debug-statement-alist))) #'(lambda () (if (string-match "linux" (buffer-file-name)) "printk(" "printf("))) Please read the documentation for `ll-debug-insert' and `ll-debug-expand' to see what is possible. If you want to teach ll-debug new modes, see `ll-debug-register-mode' and consider sending a patch to . History: 2021-03-27 alstjr7375 * Add support for rust 2020-11-28 Claus Brunzema * Prepare/cleanup for Melpa * Version 2.0.3 2020-11-26 Claus Brunzema * Small fixes and cleanup * Remove compatibility hacks (sorry xemacs...) * Add support for javascript, typescript and clojure * Version 2.0.2 2020-11-15 alstjr7375 * Deprecated lib cl to cl-lib * Active lexical binding * Version 2.0.1 2004-12-28 Claus Brunzema * Major rewrite using defstruct. * New ll-debug-insert instead of ll-debug-insert-debug-output and ll-debug-insert-variable-output. * New ll-debug-register-mode. * Version 2.0.0 2003-05-21 Claus Brunzema * Added java support. * Moved prefix calculation stuff into new ll-debug-insert-debug-output-statement. * Some cleanup. * Version 1.3.0 2003-05-15 Claus Brunzema * Added ll-debug-install-suggested-keybindings. 2003-03-10 Claus Brunzema * Added package/namespace identifiers to common lisp/c++ code * Version 1.2.6 2003-03-10 Claus Brunzema * Put in ll-debug-output-prefix instead of the hardcoded default (thanks to Stefan Kamphausen for the idea with gnuplot). * More documentation. * Version 1.2.5 2003-01-30 Claus Brunzema * added ll-debug-insert-emacs-lisp-variable-output. * ll-debug-insert-perl-variable-output doesn't insert the '$' automatically anymore. That always confused me. * various cleanup and documentation changes. * Version 1.2.3 2003-01-29 Claus Brunzema * added ll-debug-insert-perl-variable-dumper-output. 2003-01-28 Claus Brunzema * after (un)commenting a single line the point is moved to the next line. 2002-11-20 Claus Brunzema * added ll-debug-insert-scheme-variable-output. * Version 1.2.0 2002-11-11 Claus Brunzema * added ll-debug-create-next-debug-string (thanks to Scott Frazer). * updated skeletons to use ll-debug-create-next-debug-string. * Version 1.1.0 2002-11-09 Claus Brunzema * added DEBUG to skeletons. * added ll-debug-revert (thanks to Scott Frazer for the idea). * removed automatic linebreaks from skeletons, so ll-debug-revert doesn't leave half statemets behind. 2002-10-15 Claus Brunzema * fixed ll-debug-region-or-line-comment-start to look for comment-chars starting a line only (thanks to Stefan Kamphausen for the bug report). * Code cleanup. * Version 1.0.0 2002-09-04 Claus Brunzema * fixed point position after ll-debug-copy-and-comment-region-or-line * Version 0.2.2 2002-08-17 Claus Brunzema * use (search-forward comment-start ...) instead of (re-search-forward comment-start-skip ...). * use ll-debug-region-or-line-comment-start instead of the optional ignore-current-column argument for ll-debug-region-or-line-start. * ll-debug-copy-and-comment-region-or-line works correctly now if point is in the middle of the line. * Version 0.2.1 2002-08-11 Claus Brunzema * Variable output support for Common Lisp, perl and c. * Various cleanup. * Version 0.2.0 2002-08-08 Claus Brunzema * Uncommenting doesn't check the current column anymore (thanks to Stefan Kamphausen). * More blurb. * Version 0.1.1 2002-08-07 Claus Brunzema * First public version 0.1.0 ToDo: * Check if the strange log calculation in ll-debug-insert is really necessary. I want the number of C-u keypresses to dispatch alternatives on the content slot value of a ll-debug-struct, but every C-u multiplies prefix-numeric-value by 4. Is there a better way to do this? * Make preferred output stream customizable.