+File: lispref.info, Node: Edebug Execution Modes, Next: Jumping, Prev: Instrumenting, Up: Edebug
+
+Edebug Execution Modes
+----------------------
+
+ Edebug supports several execution modes for running the program you
+are debugging. We call these alternatives "Edebug execution modes"; do
+not confuse them with major or minor modes. The current Edebug
+execution mode determines how Edebug displays the progress of the
+evaluation, whether it stops at each stop point, or continues to the
+next breakpoint, for example.
+
+ Normally, you specify the Edebug execution mode by typing a command
+to continue the program in a certain mode. Here is a table of these
+commands. All except for `S' resume execution of the program, at least
+for a certain distance.
+
+`S'
+ Stop: don't execute any more of the program for now, just wait for
+ more Edebug commands (`edebug-stop').
+
+`<SPC>'
+ Step: stop at the next stop point encountered (`edebug-step-mode').
+
+`n'
+ Next: stop at the next stop point encountered after an expression
+ (`edebug-next-mode'). Also see `edebug-forward-sexp' in *Note
+ Edebug Misc::.
+
+`t'
+ Trace: pause one second at each Edebug stop point
+ (`edebug-trace-mode').
+
+`T'
+ Rapid trace: update at each stop point, but don't actually pause
+ (`edebug-Trace-fast-mode').
+
+`g'
+ Go: run until the next breakpoint (`edebug-go-mode'). *Note
+ Breakpoints::.
+
+`c'
+ Continue: pause for one second at each breakpoint, but don't stop
+ (`edebug-continue-mode').
+
+`C'
+ Rapid continue: update at each breakpoint, but don't actually pause
+ (`edebug-Continue-fast-mode').
+
+`G'
+ Go non-stop: ignore breakpoints (`edebug-Go-nonstop-mode'). You
+ can still stop the program by hitting any key.
+
+ In general, the execution modes earlier in the above list run the
+program more slowly or stop sooner.
+
+ When you enter a new Edebug level, the initial execution mode comes
+from the value of the variable `edebug-initial-mode'. By default, this
+specifies `step' mode. Note that you may reenter the same Edebug level
+several times if, for example, an instrumented function is called
+several times from one command.
+
+ While executing or tracing, you can interrupt the execution by typing
+any Edebug command. Edebug stops the program at the next stop point and
+then executes the command that you typed. For example, typing `t'
+during execution switches to trace mode at the next stop point. You can
+use `S' to stop execution without doing anything else.
+
+ If your function happens to read input, a character you hit
+intending to interrupt execution may be read by the function instead.
+You can avoid such unintended results by paying attention to when your
+program wants input.
+
+ Keyboard macros containing Edebug commands do not work; when you exit
+from Edebug, to resume the program, whether you are defining or
+executing a keyboard macro is forgotten. Also, defining or executing a
+keyboard macro outside of Edebug does not affect the command loop inside
+Edebug. This is usually an advantage. But see
+`edebug-continue-kbd-macro'.
+
+\1f
+File: lispref.info, Node: Jumping, Next: Edebug Misc, Prev: Edebug Execution Modes, Up: Edebug
+
+Jumping
+-------
+
+ Commands described here let you jump to a specified location. All,
+except `i', use temporary breakpoints to establish the stop point and
+then switch to `go' mode. Any other breakpoint reached before the
+intended stop point will also stop execution. See *Note Breakpoints::
+for the details on breakpoints.
+
+`f'
+ Run the program forward over one expression
+ (`edebug-forward-sexp'). More precisely, set a temporary
+ breakpoint at the position that `C-M-f' would reach, then execute
+ in `go' mode so that the program will stop at breakpoints.
+
+ With a prefix argument N, the temporary breakpoint is placed N
+ sexps beyond point. If the containing list ends before N more
+ elements, then the place to stop is after the containing
+ expression.
+
+ Be careful that the position `C-M-f' finds is a place that the
+ program will really get to; this may not be true in a `cond', for
+ example.
+
+ This command does `forward-sexp' starting at point rather than the
+ stop point. If you want to execute one expression from the
+ current stop point, type `w' first, to move point there.
+
+`o'
+ Continue "out of" an expression (`edebug-step-out'). It places a
+ temporary breakpoint at the end of the sexp containing point.
+
+ If the containing sexp is a function definition itself, it
+ continues until just before the last sexp in the definition. If
+ that is where you are now, it returns from the function and then
+ stops. In other words, this command does not exit the currently
+ executing function unless you are positioned after the last sexp.
+
+`I'
+ Step into the function or macro after point after first ensuring
+ that it is instrumented. It does this by calling
+ `edebug-on-entry' and then switching to `go' mode.
+
+ Although the automatic instrumentation is convenient, it is not
+ later automatically uninstrumented.
+
+`h'
+ Proceed to the stop point near where point is using a temporary
+ breakpoint (`edebug-goto-here').
+
+ All the commands in this section may fail to work as expected in case
+of nonlocal exit, because a nonlocal exit can bypass the temporary
+breakpoint where you expected the program to stop.
+
+\1f
+File: lispref.info, Node: Edebug Misc, Next: Breakpoints, Prev: Jumping, Up: Edebug
+
+Miscellaneous
+-------------
+
+ Some miscellaneous commands are described here.
+
+`?'
+ Display the help message for Edebug (`edebug-help').
+
+`C-]'
+ Abort one level back to the previous command level
+ (`abort-recursive-edit').
+
+`q'
+ Return to the top level editor command loop (`top-level'). This
+ exits all recursive editing levels, including all levels of Edebug
+ activity. However, instrumented code protected with
+ `unwind-protect' or `condition-case' forms may resume debugging.
+
+`Q'
+ Like `q' but don't stop even for protected code
+ (`top-level-nonstop').
+
+`r'
+ Redisplay the most recently known expression result in the echo
+ area (`edebug-previous-result').
+
+`d'
+ Display a backtrace, excluding Edebug's own functions for clarity
+ (`edebug-backtrace').
+
+ You cannot use debugger commands in the backtrace buffer in Edebug
+ as you would in the standard debugger.
+
+ The backtrace buffer is killed automatically when you continue
+ execution.
+
+ From the Edebug recursive edit, you may invoke commands that activate
+Edebug again recursively. Any time Edebug is active, you can quit to
+the top level with `q' or abort one recursive edit level with `C-]'.
+You can display a backtrace of all the pending evaluations with `d'.
+
+\1f
+File: lispref.info, Node: Breakpoints, Next: Trapping Errors, Prev: Edebug Misc, Up: Edebug
+
+Breakpoints
+-----------
+
+ There are three more ways to stop execution once it has started:
+breakpoints, the global break condition, and embedded breakpoints.
+
+ While using Edebug, you can specify "breakpoints" in the program you
+are testing: points where execution should stop. You can set a
+breakpoint at any stop point, as defined in *Note Using Edebug::. For
+setting and unsetting breakpoints, the stop point that is affected is
+the first one at or after point in the source code buffer. Here are the
+Edebug commands for breakpoints:
+
+`b'
+ Set a breakpoint at the stop point at or after point
+ (`edebug-set-breakpoint'). If you use a prefix argument, the
+ breakpoint is temporary (it turns off the first time it stops the
+ program).
+
+`u'
+ Unset the breakpoint (if any) at the stop point at or after the
+ current point (`edebug-unset-breakpoint').
+
+`x CONDITION <RET>'
+ Set a conditional breakpoint which stops the program only if
+ CONDITION evaluates to a non-`nil' value
+ (`edebug-set-conditional-breakpoint'). If you use a prefix
+ argument, the breakpoint is temporary (it turns off the first time
+ it stops the program).
+
+`B'
+ Move point to the next breakpoint in the definition
+ (`edebug-next-breakpoint').
+
+ While in Edebug, you can set a breakpoint with `b' and unset one
+with `u'. First you must move point to a position at or before the
+desired Edebug stop point, then hit the key to change the breakpoint.
+Unsetting a breakpoint that has not been set does nothing.
+
+ Reevaluating or reinstrumenting a definition clears all its
+breakpoints.
+
+ A "conditional breakpoint" tests a condition each time the program
+gets there. To set a conditional breakpoint, use `x', and specify the
+condition expression in the minibuffer. Setting a conditional
+breakpoint at a stop point that already has a conditional breakpoint
+puts the current condition expression in the minibuffer so you can edit
+it.
+
+ You can make both conditional and unconditional breakpoints
+"temporary" by using a prefix arg to the command to set the breakpoint.
+After breaking at a temporary breakpoint, it is automatically cleared.
+
+ Edebug always stops or pauses at a breakpoint except when the Edebug
+mode is `Go-nonstop'. In that mode, it ignores breakpoints entirely.
+
+ To find out where your breakpoints are, use `B', which moves point
+to the next breakpoint in the definition following point, or to the
+first breakpoint if there are no following breakpoints. This command
+does not continue execution--it just moves point in the buffer.
+
+* Menu:
+
+* Global Break Condition:: Breaking on an event.
+* Embedded Breakpoints:: Embedding breakpoints in code.
+
+\1f
+File: lispref.info, Node: Global Break Condition, Next: Embedded Breakpoints, Up: Breakpoints
+
+Global Break Condition
+......................
+
+ In contrast to breaking when execution reaches specified locations,
+you can also cause a break when a certain event occurs. The "global
+break condition" is a condition that is repeatedly evaluated at every
+stop point. If it evaluates to a non-`nil' value, then execution is
+stopped or paused depending on the execution mode, just like a
+breakpoint. Any errors that might occur as a result of evaluating the
+condition are ignored, as if the result were `nil'.
+
+ You can set or edit the condition expression, stored in
+`edebug-global-break-condition', using `X'
+(`edebug-set-global-break-condition').
+
+ Using the global break condition is perhaps the fastest way to find
+where in your code some event occurs, but since it is rather expensive
+you should reset the condition to `nil' when not in use.
+
+\1f
+File: lispref.info, Node: Embedded Breakpoints, Prev: Global Break Condition, Up: Breakpoints
+
+Embedded Breakpoints
+....................
+
+ Since all breakpoints in a definition are cleared each time you
+reinstrument it, you might rather create an "embedded breakpoint" which
+is simply a call to the function `edebug'. You can, of course, make
+such a call conditional. For example, in the `fac' function, 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, Edebug will stop before the call to `edebug'. Depending on the
+execution mode, Edebug will stop or pause.
+
+ However, if no instrumented code is being executed, calling `edebug'
+will instead invoke `debug'. Calling `debug' will always invoke the
+standard backtrace debugger.
+
+\1f