path: root/devdocs/elisp/explicit-debug.html

 <h4 class="subsection">Explicit Entry to the Debugger</h4>    <p>You can cause the debugger to be called at a certain point in your program by writing the expression <code>(debug)</code> at that point. To do this, visit the source file, insert the text ‘<samp>(debug)</samp>’ at the proper place, and type <kbd>C-M-x</kbd> (<code>eval-defun</code>, a Lisp mode key binding). <strong>Warning:</strong> if you do this for temporary debugging purposes, be sure to undo this insertion before you save the file! </p> <p>The place where you insert ‘<samp>(debug)</samp>’ must be a place where an additional form can be evaluated and its value ignored. (If the value of <code>(debug)</code> isn’t ignored, it will alter the execution of the program!) The most common suitable places are inside a <code>progn</code> or an implicit <code>progn</code> (see <a href="sequencing">Sequencing</a>). </p> <p>If you don’t know exactly where in the source code you want to put the debug statement, but you want to display a backtrace when a certain message is displayed, you can set <code>debug-on-message</code> to a regular expression matching the desired message. </p><div class="_attribution">
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    Copyright &copy; 1990-1996, 1998-2022 Free Software Foundation, Inc. <br>Licensed under the GNU GPL license.<br>
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