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(elisp)Source Breakpoints

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Source Breakpoints
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   All breakpoints in a definition are forgotten each time you
reinstrument it.  If you wish to make a breakpoint that won't be
forgotten, you can write a "source breakpoint", which is simply a call
to the function `edebug' in your source code.  You can, of course, make
such a call conditional.  For example, in the `fac' function, you can
insert the first line as shown below, to stop when the argument reaches
zero:

     (defun fac (n)
       (if (= n 0) (edebug))
       (if (< 0 n)
           (* n (fac (1- n)))
         1))

   When the `fac' definition is instrumented and the function is
called, the call to `edebug' acts as a breakpoint.  Depending on the
execution mode, Edebug stops or pauses there.

   If no instrumented code is being executed when `edebug' is called,
that function calls `debug'.