22.4.13 Tracing

In addition to automatic stepping through source code, which is also called tracing (see Edebug Execution Modes), Edebug can produce a traditional trace listing of execution in a separate buffer, ‘*edebug-trace*’.

If the variable edebug-trace is non-nil, each function entry and exit adds lines to the trace buffer. On function entry, Edebug prints ‘::::{’ followed by the function name and argument values. On function exit, Edebug prints ‘::::}’ followed by the function name and result of the function. The number of ‘:’s is computed from the recursion depth. The balanced braces in the trace buffer can be used to find the matching beginning or end of function calls. These displays may be customized by replacing the functions edebug-print-trace-before and edebug-print-trace-after, which take an arbitrary message string to print.

The macro edebug-tracing provides tracing similar to function enter and exit tracing, but for arbitrary expressions. This macro should be explicitly inserted by you around expressions you wish to trace the execution of. The first argument is a message string (evaluated), and the rest are expressions to evaluate. The result of the last expression is returned.

Finally, you can insert arbitrary strings into the trace buffer with explicit calls to edebug-trace. The arguments of this function are the same as for message, but a newline is always inserted after each string printed in this way.

edebug-tracing and edebug-trace insert lines in the trace buffer even if Edebug is not active. Every time the trace buffer is added to, the window is scrolled to show the last lines inserted. (There may be some display problems if you use tracing along with the evaluation list.)