This is Info file elisp, produced by Makeinfo version 1.68 from the input file elisp.texi. INFO-DIR-SECTION Editors START-INFO-DIR-ENTRY * Elisp: (elisp). The Emacs Lisp Reference Manual. END-INFO-DIR-ENTRY This version is the edition 2.5 of the GNU Emacs Lisp Reference Manual. It corresponds to Emacs Version 20.3 Published by the Free Software Foundation 59 Temple Place, Suite 330 Boston, MA 02111-1307 USA Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled "GNU General Public License" is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled "GNU General Public License" may be included in a translation approved by the Free Software Foundation instead of in the original English.  File: elisp, Node: Edebug, Next: Syntax Errors, Prev: Debugger, Up: Debugging Edebug ====== Edebug is a source-level debugger for Emacs Lisp programs with which you can: * Step through evaluation, stopping before and after each expression. * Set conditional or unconditional breakpoints. * Stop when a specified condition is true (the global break event). * Trace slow or fast, stopping briefly at each stop point, or at each breakpoint. * Display expression results and evaluate expressions as if outside of Edebug. * Automatically re-evaluate a list of expressions and display their results each time Edebug updates the display. * Output trace info on function enter and exit. * Stop when an error occurs. * Display a backtrace, omitting Edebug's own frames. * Specify argument evaluation for macros and defining forms. * Obtain rudimentary coverage testing and frequency counts. The first three sections below should tell you enough about Edebug to enable you to use it. * Menu: * Using Edebug:: Introduction to use of Edebug. * Instrumenting:: You must instrument your code in order to debug it with Edebug. * Modes: Edebug Execution Modes. Execution modes, stopping more or less often. * Jumping:: Commands to jump to a specified place. * Misc: Edebug Misc. Miscellaneous commands. * Breakpoints:: Setting breakpoints to make the program stop. * Trapping Errors:: trapping errors with Edebug. * Views: Edebug Views. Views inside and outside of Edebug. * Eval: Edebug Eval. Evaluating expressions within Edebug. * Eval List:: Expressions whose values are displayed each time you enter Edebug. * Printing in Edebug:: Customization of printing. * Trace Buffer:: How to produce trace output in a buffer. * Coverage Testing:: How to test evaluation coverage. * The Outside Context:: Data that Edebug saves and restores. * Instrumenting Macro Calls:: Specifying how to handle macro calls. * Options: Edebug Options. Option variables for customizing Edebug.  File: elisp, Node: Using Edebug, Next: Instrumenting, Up: Edebug Using Edebug ------------ To debug a Lisp program with Edebug, you must first "instrument" the Lisp code that you want to debug. A simple way to do this is to first move point into the definition of a function or macro and then do `C-u C-M-x' (`eval-defun' with a prefix argument). See *Note Instrumenting::, for alternative ways to instrument code. Once a function is instrumented, any call to the function activates Edebug. Activating Edebug may stop execution and let you step through the function, or it may update the display and continue execution while checking for debugging commands, depending on which Edebug execution mode you have selected. The default execution mode is step, which does stop execution. *Note Edebug Execution Modes::. Within Edebug, you normally view an Emacs buffer showing the source of the Lisp code you are debugging. This is referred to as the "source code buffer". This buffer is temporarily read-only. An arrow at the left margin indicates the line where the function is executing. Point initially shows where within the line the function is executing, but this ceases to be true if you move point yourself. If you instrument the definition of `fac' (shown below) and then execute `(fac 3)', here is what you normally see. Point is at the open-parenthesis before `if'. (defun fac (n) =>-!-(if (< 0 n) (* n (fac (1- n))) 1)) The places within a function where Edebug can stop execution are called "stop points". These occur both before and after each subexpression that is a list, and also after each variable reference. Here we show with periods the stop points found in the function `fac': (defun fac (n) .(if .(< 0 n.). .(* n. .(fac (1- n.).).). 1).) The special commands of Edebug are available in the source code buffer in addition to the commands of Emacs Lisp mode. For example, you can type the Edebug command to execute until the next stop point. If you type once after entry to `fac', here is the display you will see: (defun fac (n) =>(if -!-(< 0 n) (* n (fac (1- n))) 1)) When Edebug stops execution after an expression, it displays the expression's value in the echo area. Other frequently used commands are `b' to set a breakpoint at a stop point, `g' to execute until a breakpoint is reached, and `q' to exit Edebug and return to the top-level command loop. Type `?' to display a list of all Edebug commands.  File: elisp, Node: Instrumenting, Next: Edebug Execution Modes, Prev: Using Edebug, Up: Edebug Instrumenting for Edebug ------------------------ In order to use Edebug to debug Lisp code, you must first "instrument" the code. Instrumenting code inserts additional code into it, to invoke Edebug at the proper places. Once you have loaded Edebug, the command `C-M-x' (`eval-defun') is redefined so that when invoked with a prefix argument on a definition, it instruments the definition before evaluating it. (The source code itself is not modified.) If the variable `edebug-all-defs' is non-`nil', that inverts the meaning of the prefix argument: then `C-M-x' instruments the definition *unless* it has a prefix argument. The default value of `edebug-all-defs' is `nil'. The command `M-x edebug-all-defs' toggles the value of the variable `edebug-all-defs'. If `edebug-all-defs' is non-`nil', then the commands `eval-region', `eval-current-buffer', and `eval-buffer' also instrument any definitions they evaluate. Similarly, `edebug-all-forms' controls whether `eval-region' should instrument *any* form, even non-defining forms. This doesn't apply to loading or evaluations in the minibuffer. The command `M-x edebug-all-forms' toggles this option. Another command, `M-x edebug-eval-top-level-form', is available to instrument any top-level form regardless of the values of `edebug-all-defs' and `edebug-all-forms'. While Edebug is active, the command `I' (`edebug-instrument-callee') instruments the definition of the function or macro called by the list form after point, if is not already instrumented. This is possible only if Edebug knows where to find the source for that function; after loading Edebug, `eval-region' records the position of every definition it evaluates, even if not instrumenting it. See also the `i' command (*note Jumping::.), which steps into the call after instrumenting the function. Edebug knows how to instrument all the standard special forms, `interactive' forms with an expression argument, anonymous lambda expressions, and other defining forms. Edebug cannot know what a user-defined macro will do with the arguments of a macro call, so you must tell it; see *Note Instrumenting Macro Calls::, for details. When Edebug is about to instrument code for the first time in a session, it runs the hook `edebug-setup-hook', then sets it to `nil'. You can use this to arrange to load Edebug specifications (*note Instrumenting Macro Calls::.) associated with a package you are using, but actually load them only if you use Edebug. To remove instrumentation from a definition, simply re-evaluate its definition in a way that does not instrument. There are two ways of evaluating forms that never instrument them: from a file with `load', and from the minibuffer with `eval-expression' (`M-:'). If Edebug detects a syntax error while instrumenting, it leaves point at the erroneous code and signals an `invalid-read-syntax' error. *Note Edebug Eval::, for other evaluation functions available inside of Edebug.  File: elisp, 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 far Edebug continues execution before stopping--whether it stops at each stop point, or continues to the next breakpoint, for example--and how much Edebug displays the progress of the evaluation before it stops. 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'). `' 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 the display 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 one second at each breakpoint, and then continue (`edebug-continue-mode'). `C' Rapid continue: move point to each breakpoint, but don't pause (`edebug-Continue-fast-mode'). `G' Go non-stop: ignore breakpoints (`edebug-Go-nonstop-mode'). You can still stop the program by typing `S', or any editing command. In general, the execution modes earlier in the above list run the program more slowly or stop sooner than the modes later in the list. 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 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 type 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 the commands in this section do not completely work: exiting from Edebug, to resume the program, loses track of the keyboard macro. This is not easy to fix. Also, defining or executing a keyboard macro outside of Edebug does not affect commands inside Edebug. This is usually an advantage. But see the `edebug-continue-kbd-macro' option (*note Edebug Options::.). 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.  File: elisp, Node: Jumping, Next: Edebug Misc, Prev: Edebug Execution Modes, Up: Edebug Jumping ------- The commands described in this section execute until they reach a specified location. All except `i' make a temporary breakpoint to establish the place to stop, then switch to go mode. Any other breakpoint reached before the intended stop point will also stop execution. *Note Breakpoints::, for the details on breakpoints. These commands 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. `h' Proceed to the stop point near where point is (`edebug-goto-here'). `f' Run the program forward over one expression (`edebug-forward-sexp'). `o' Run the program until the end of the containing sexp. `i' Step into the function or macro called by the form after point. The `h' command proceeds to the stop point near the current location of point, using a temporary breakpoint. See *Note Breakpoints::, for more information about breakpoints. The `f' command runs the program forward over one expression. More precisely, it sets a temporary breakpoint at the position that `C-M-f' would reach, then executes 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. The `f' command does `forward-sexp' starting at point, rather than at the stop point, for flexibility. If you want to execute one expression *from the current stop point*, type `w' first, to move point there, and then type `f'. The `o' command continues "out of" an expression. It places a temporary breakpoint at the end of the sexp containing point. If the containing sexp is a function definition itself, `o' 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. The `i' command steps into the function or macro called by the list form after point, and stops at its first stop point. Note that the form need not be the one about to be evaluated. But if the form is a function call about to be evaluated, remember to use this command before any of the arguments are evaluated, since otherwise it will be too late. The `i' command instruments the function or macro it's supposed to step into, if it isn't instrumented already. This is convenient, but keep in mind that the function or macro remains instrumented unless you explicitly arrange to deinstrument it.  File: elisp, Node: Edebug Misc, Next: Breakpoints, Prev: Jumping, Up: Edebug Miscellaneous Edebug Commands ----------------------------- Some miscellaneous Edebug 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'.  File: elisp, Node: Breakpoints, Next: Trapping Errors, Prev: Edebug Misc, Up: Edebug Breakpoints ----------- Edebug's step mode stops execution at the next stop point reached. There are three other ways to stop Edebug execution once it has started: breakpoints, the global break condition, and source 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 point (`edebug-unset-breakpoint'). `x CONDITION ' Set a conditional breakpoint which stops the program only if CONDITION evaluates to a non-`nil' value (`edebug-set-conditional-breakpoint'). With a prefix argument, the breakpoint is temporary. `B' Move point to the next breakpoint in the current definition (`edebug-next-breakpoint'). While in Edebug, you can set a breakpoint with `b' and unset one with `u'. First move point to the Edebug stop point of your choice, then type `b' or `u' to set or unset a breakpoint there. Unsetting a breakpoint where none has been set has no effect. Re-evaluating or reinstrumenting a definition forgets all its breakpoints. A "conditional breakpoint" tests a condition each time the program gets there. Any errors that occur as a result of evaluating the condition are ignored, as if the result were `nil'. To set a conditional breakpoint, use `x', and specify the condition expression in the minibuffer. Setting a conditional breakpoint at a stop point that has a previously established conditional breakpoint puts the previous condition expression in the minibuffer so you can edit it. You can make a conditional or unconditional breakpoint "temporary" by using a prefix argument with the command to set the breakpoint. When a temporary breakpoint stops the program, it is automatically unset. 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 the `B' command, which moves point to the next breakpoint following point, within the same function, 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. * Source Breakpoints:: Embedding breakpoints in source code.  File: elisp, Node: Global Break Condition, Next: Source Breakpoints, Up: Breakpoints Global Break Condition ...................... A "global break condition" stops execution when a specified condition is satisfied, no matter where that may occur. Edebug evaluates the global break condition at every stop point. If it evaluates to a non-`nil' value, then execution stops or pauses depending on the execution mode, as if a breakpoint had been hit. If evaluating the condition gets an error, execution does not stop. The condition expression is stored in `edebug-global-break-condition'. You can specify a new expression using the `X' command (`edebug-set-global-break-condition'). The global break condition is the simplest way to find where in your code some event occurs, but it makes code run much more slowly. So you should reset the condition to `nil' when not using it.  File: elisp, Node: Source Breakpoints, Prev: Global Break Condition, Up: Breakpoints Source Breakpoints .................. All breakpoints in a definition are forgotten each time you reinstrument it. 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, 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'.  File: elisp, Node: Trapping Errors, Next: Edebug Views, Prev: Breakpoints, Up: Edebug Trapping Errors --------------- Emacs normally displays an error message when an error is signaled and not handled with `condition-case'. While Edebug is active and executing instrumented code, it normally responds to all unhandled errors. You can customize this with the options `edebug-on-error' and `edebug-on-quit'; see *Note Edebug Options::. When Edebug responds to an error, it shows the last stop point encountered before the error. This may be the location of a call to a function which was not instrumented, within which the error actually occurred. For an unbound variable error, the last known stop point might be quite distant from the offending variable reference. In that case you might want to display a full backtrace (*note Edebug Misc::.). If you change `debug-on-error' or `debug-on-quit' while Edebug is active, these changes will be forgotten when Edebug becomes inactive. Furthermore, during Edebug's recursive edit, these variables are bound to the values they had outside of Edebug.  File: elisp, Node: Edebug Views, Next: Edebug Eval, Prev: Trapping Errors, Up: Edebug Edebug Views ------------ These Edebug commands let you view aspects of the buffer and window status as they were before entry to Edebug. The outside window configuration is the collection of windows and contents that were in effect outside of Edebug. `v' Temporarily view the outside window configuration (`edebug-view-outside'). `p' Temporarily display the outside current buffer with point at its outside position (`edebug-bounce-point'). With a prefix argument N, pause for N seconds instead. `w' Move point back to the current stop point in the source code buffer (`edebug-where'). If you use this command in a different window displaying the same buffer, that window will be used instead to display the current definition in the future. `W' Toggle whether Edebug saves and restores the outside window configuration (`edebug-toggle-save-windows'). With a prefix argument, `W' only toggles saving and restoring of the selected window. To specify a window that is not displaying the source code buffer, you must use `C-x X W' from the global keymap. You can view the outside window configuration with `v' or just bounce to the point in the current buffer with `p', even if it is not normally displayed. After moving point, you may wish to jump back to the stop point with `w' from a source code buffer. Each time you use `W' to turn saving *off*, Edebug forgets the saved outside window configuration--so that even if you turn saving back *on*, the current window configuration remains unchanged when you next exit Edebug (by continuing the program). However, the automatic redisplay of `*edebug*' and `*edebug-trace*' may conflict with the buffers you wish to see unless you have enough windows open.  File: elisp, Node: Edebug Eval, Next: Eval List, Prev: Edebug Views, Up: Edebug Evaluation ---------- While within Edebug, you can evaluate expressions "as if" Edebug were not running. Edebug tries to be invisible to the expression's evaluation and printing. Evaluation of expressions that cause side effects will work as expected except for things that Edebug explicitly saves and restores. *Note The Outside Context::, for details on this process. `e EXP ' Evaluate expression EXP in the context outside of Edebug (`edebug-eval-expression'). That is, Edebug tries to minimize its interference with the evaluation. `M-: EXP ' Evaluate expression EXP in the context of Edebug itself. `C-x C-e' Evaluate the expression before point, in the context outside of Edebug (`edebug-eval-last-sexp'). Edebug supports evaluation of expressions containing references to lexically bound symbols created by the following constructs in `cl.el' (version 2.03 or later): `lexical-let', `macrolet', and `symbol-macrolet'.  File: elisp, Node: Eval List, Next: Printing in Edebug, Prev: Edebug Eval, Up: Edebug Evaluation List Buffer ---------------------- You can use the "evaluation list buffer", called `*edebug*', to evaluate expressions interactively. You can also set up the "evaluation list" of expressions to be evaluated automatically each time Edebug updates the display. `E' Switch to the evaluation list buffer `*edebug*' (`edebug-visit-eval-list'). In the `*edebug*' buffer you can use the commands of Lisp Interaction mode (*note Lisp Interaction: (emacs)Lisp Interaction.) as well as these special commands: `C-j' Evaluate the expression before point, in the outside context, and insert the value in the buffer (`edebug-eval-print-last-sexp'). `C-x C-e' Evaluate the expression before point, in the context outside of Edebug (`edebug-eval-last-sexp'). `C-c C-u' Build a new evaluation list from the contents of the buffer (`edebug-update-eval-list'). `C-c C-d' Delete the evaluation list group that point is in (`edebug-delete-eval-item'). `C-c C-w' Switch back to the source code buffer at the current stop point (`edebug-where'). You can evaluate expressions in the evaluation list window with `C-j' or `C-x C-e', just as you would in `*scratch*'; but they are evaluated in the context outside of Edebug. The expressions you enter interactively (and their results) are lost when you continue execution; but you can set up an "evaluation list" consisting of expressions to be evaluated each time execution stops. To do this, write one or more "evaluation list groups" in the evaluation list buffer. An evaluation list group consists of one or more Lisp expressions. Groups are separated by comment lines. The command `C-c C-u' (`edebug-update-eval-list') rebuilds the evaluation list, scanning the buffer and using the first expression of each group. (The idea is that the second expression of the group is the value previously computed and displayed.) Each entry to Edebug redisplays the evaluation list by inserting each expression in the buffer, followed by its current value. It also inserts comment lines so that each expression becomes its own group. Thus, if you type `C-c C-u' again without changing the buffer text, the evaluation list is effectively unchanged. If an error occurs during an evaluation from the evaluation list, the error message is displayed in a string as if it were the result. Therefore, expressions that use variables not currently valid do not interrupt your debugging. Here is an example of what the evaluation list window looks like after several expressions have been added to it: (current-buffer) # ;--------------------------------------------------------------- (selected-window) # ;--------------------------------------------------------------- (point) 196 ;--------------------------------------------------------------- bad-var "Symbol's value as variable is void: bad-var" ;--------------------------------------------------------------- (recursion-depth) 0 ;--------------------------------------------------------------- this-command eval-last-sexp ;--------------------------------------------------------------- To delete a group, move point into it and type `C-c C-d', or simply delete the text for the group and update the evaluation list with `C-c C-u'. To add a new expression to the evaluation list, insert the expression at a suitable place, and insert a new comment line. (You need not insert dashes in the comment line--its contents don't matter.) Then type `C-c C-u'. After selecting `*edebug*', you can return to the source code buffer with `C-c C-w'. The `*edebug*' buffer is killed when you continue execution, and recreated next time it is needed.  File: elisp, Node: Printing in Edebug, Next: Trace Buffer, Prev: Eval List, Up: Edebug Printing in Edebug ------------------ If an expression in your program produces a value containing circular list structure, you may get an error when Edebug attempts to print it. One way to cope with circular structure is to set `print-length' or `print-level' to truncate the printing. Edebug does this for you; it binds `print-length' and `print-level' to 50 if they were `nil'. (Actually, the variables `edebug-print-length' and `edebug-print-level' specify the values to use within Edebug.) *Note Output Variables::. - User Option: edebug-print-length If non-`nil', bind `print-length' to this while printing results in Edebug. The default value is `50'. - User Option: edebug-print-level If non-`nil', bind `print-level' to this while printing results in Edebug. The default value is `50'. You can also print circular structures and structures that share elements more informatively by using the `cust-print' package. To load `cust-print' and activate custom printing only for Edebug, simply use the command `M-x edebug-install-custom-print'. To restore the standard print functions, use `M-x edebug-uninstall-custom-print'. Here is an example of code that creates a circular structure: (setq a '(x y)) (setcar a a) Custom printing prints this as `Result: #1=(#1# y)'. The `#1=' notation labels the structure that follows it with the label `1', and the `#1#' notation references the previously labeled structure. This notation is used for any shared elements of lists or vectors. - User Option: edebug-print-circle If non-`nil', bind `print-circle' to this while printing results in Edebug. The default value is `nil'. Other programs can also use custom printing; see `cust-print.el' for details.  File: elisp, Node: Trace Buffer, Next: Coverage Testing, Prev: Printing in Edebug, Up: Edebug Trace Buffer ------------ Edebug can record an execution trace, storing it in a buffer named `*edebug-trace*'. This is a log of function calls and returns, showing the function names and their arguments and values. To enable trace recording, set `edebug-trace' to a non-`nil' value. Making a trace buffer is not the same thing as using trace execution mode (*note Edebug Execution Modes::.). When trace recording is enabled, each function entry and exit adds lines to the trace buffer. A function entry record looks like `::::{' followed by the function name and argument values. A function exit record looks like `::::}' followed by the function name and result of the function. The number of `:'s in an entry shows its recursion depth. You can use the braces in the trace buffer to find the matching beginning or end of function calls. You can customize trace recording for function entry and exit by redefining the functions `edebug-print-trace-before' and `edebug-print-trace-after'. - Macro: edebug-tracing STRING BODY... This macro requests additional trace information around the execution of the BODY forms. The argument STRING specifies text to put in the trace buffer. All the arguments are evaluated. `edebug-tracing' returns the value of the last form in BODY. - Function: edebug-trace FORMAT-STRING &rest FORMAT-ARGS This function inserts text in the trace buffer. It computes the text with `(apply 'format FORMAT-STRING FORMAT-ARGS)'. It also appends a newline to separate entries. `edebug-tracing' and `edebug-trace' insert lines in the trace buffer whenever they are called, even if Edebug is not active. Adding text to the trace buffer also scrolls its window to show the last lines inserted.  File: elisp, Node: Coverage Testing, Next: The Outside Context, Prev: Trace Buffer, Up: Edebug Coverage Testing ---------------- Edebug provides rudimentary coverage testing and display of execution frequency. Coverage testing works by comparing the result of each expression with the previous result; each form in the program is considered "covered" if it has returned two different values since you began testing coverage in the current Emacs session. Thus, to do coverage testing on your program, execute it under various conditions and note whether it behaves correctly; Edebug will tell you when you have tried enough different conditions that each form has returned two different values. Coverage testing makes execution slower, so it is only done if `edebug-test-coverage' is non-`nil'. Frequency counting is performed for all execution of an instrumented function, even if the execution mode is Go-nonstop, and regardless of whether coverage testing is enabled. Use `M-x edebug-display-freq-count' to display both the coverage information and the frequency counts for a definition. - Command: edebug-display-freq-count This command displays the frequency count data for each line of the current definition. The frequency counts appear as comment lines after each line of code, and you can undo all insertions with one `undo' command. The counts appear under the `(' before an expression or the `)' after an expression, or on the last character of a variable. To simplify the display, a count is not shown if it is equal to the count of an earlier expression on the same line. The character `=' following the count for an expression says that the expression has returned the same value each time it was evaluated. In other words, it is not yet "covered" for coverage testing purposes. To clear the frequency count and coverage data for a definition, simply reinstrument it with `eval-defun'. For example, after evaluating `(fac 5)' with a source breakpoint, and setting `edebug-test-coverage' to `t', when the breakpoint is reached, the frequency data looks like this: (defun fac (n) (if (= n 0) (edebug)) ;#6 1 0 =5 (if (< 0 n) ;#5 = (* n (fac (1- n))) ;# 5 0 1)) ;# 0 The comment lines show that `fac' was called 6 times. The first `if' statement returned 5 times with the same result each time; the same is true of the condition on the second `if'. The recursive call of `fac' did not return at all.  File: elisp, Node: The Outside Context, Next: Instrumenting Macro Calls, Prev: Coverage Testing, Up: Edebug The Outside Context ------------------- Edebug tries to be transparent to the program you are debugging, but it does not succeed completely. Edebug also tries to be transparent when you evaluate expressions with `e' or with the evaluation list buffer, by temporarily restoring the outside context. This section explains precisely what context Edebug restores, and how Edebug fails to be completely transparent. * Menu: * Checking Whether to Stop:: When Edebug decides what to do. * Edebug Display Update:: When Edebug updates the display. * Edebug Recursive Edit:: When Edebug stops execution.  File: elisp, Node: Checking Whether to Stop, Next: Edebug Display Update, Up: The Outside Context Checking Whether to Stop ........................ Whenever Edebug is entered, it needs to save and restore certain data before even deciding whether to make trace information or stop the program. * `max-lisp-eval-depth' and `max-specpdl-size' are both incremented once to reduce Edebug's impact on the stack. You could, however, still run out of stack space when using Edebug. * The state of keyboard macro execution is saved and restored. While Edebug is active, `executing-macro' is bound to `edebug-continue-kbd-macro'.  File: elisp, Node: Edebug Display Update, Next: Edebug Recursive Edit, Prev: Checking Whether to Stop, Up: The Outside Context Edebug Display Update ..................... When Edebug needs to display something (e.g., in trace mode), it saves the current window configuration from "outside" Edebug (*note Window Configurations::.). When you exit Edebug (by continuing the program), it restores the previous window configuration. Emacs redisplays only when it pauses. Usually, when you continue execution, the program comes back into Edebug at a breakpoint or after stepping without pausing or reading input in between. In such cases, Emacs never gets a chance to redisplay the "outside" configuration. What you see is the same window configuration as the last time Edebug was active, with no interruption. Entry to Edebug for displaying something also saves and restores the following data, but some of these are deliberately not restored if an error or quit signal occurs. * Which buffer is current, and the positions of point and the mark in the current buffer, are saved and restored. * The outside window configuration is saved and restored if `edebug-save-windows' is non-`nil' (*note Edebug Display Update::.). The window configuration is not restored on error or quit, but the outside selected window *is* reselected even on error or quit in case a `save-excursion' is active. If the value of `edebug-save-windows' is a list, only the listed windows are saved and restored. The window start and horizontal scrolling of the source code buffer are not restored, however, so that the display remains coherent within Edebug. * The value of point in each displayed buffer is saved and restored if `edebug-save-displayed-buffer-points' is non-`nil'. * The variables `overlay-arrow-position' and `overlay-arrow-string' are saved and restored. So you can safely invoke Edebug from the recursive edit elsewhere in the same buffer. * `cursor-in-echo-area' is locally bound to `nil' so that the cursor shows up in the window.  File: elisp, Node: Edebug Recursive Edit, Prev: Edebug Display Update, Up: The Outside Context Edebug Recursive Edit ..................... When Edebug is entered and actually reads commands from the user, it saves (and later restores) these additional data: * The current match data. *Note Match Data::. * `last-command', `this-command', `last-command-char', `last-input-char', `last-input-event', `last-command-event', `last-event-frame', `last-nonmenu-event', and `track-mouse'. Commands used within Edebug do not affect these variables outside of Edebug. The key sequence returned by `this-command-keys' is changed by executing commands within Edebug and there is no way to reset the key sequence from Lisp. Edebug cannot save and restore the value of `unread-command-events'. Entering Edebug while this variable has a nontrivial value can interfere with execution of the program you are debugging. * Complex commands executed while in Edebug are added to the variable `command-history'. In rare cases this can alter execution. * Within Edebug, the recursion depth appears one deeper than the recursion depth outside Edebug. This is not true of the automatically updated evaluation list window. * `standard-output' and `standard-input' are bound to `nil' by the `recursive-edit', but Edebug temporarily restores them during evaluations. * The state of keyboard macro definition is saved and restored. While Edebug is active, `defining-kbd-macro' is bound to `edebug-continue-kbd-macro'.  File: elisp, Node: Instrumenting Macro Calls, Next: Edebug Options, Prev: The Outside Context, Up: Edebug Instrumenting Macro Calls ------------------------- When Edebug instruments an expression that calls a Lisp macro, it needs additional information about the macro to do the job properly. This is because there is no a-priori way to tell which subexpressions of the macro call are forms to be evaluated. (Evaluation may occur explicitly in the macro body, or when the resulting expansion is evaluated, or any time later.) Therefore, you must define an Edebug specification for each macro that Edebug will encounter, to explain the format of calls to that macro. To do this, use `def-edebug-spec'. - Macro: def-edebug-spec MACRO SPECIFICATION Specify which expressions of a call to macro MACRO are forms to be evaluated. For simple macros, the SPECIFICATION often looks very similar to the formal argument list of the macro definition, but specifications are much more general than macro arguments. The MACRO argument can actually be any symbol, not just a macro name. Here is a simple example that defines the specification for the `for' example macro (*note Argument Evaluation::.), followed by an alternative, equivalent specification. (def-edebug-spec for (symbolp "from" form "to" form "do" &rest form)) (def-edebug-spec for (symbolp ['from form] ['to form] ['do body])) Here is a table of the possibilities for SPECIFICATION and how each directs processing of arguments. `t' All arguments are instrumented for evaluation. `0' None of the arguments is instrumented. a symbol The symbol must have an Edebug specification which is used instead. This indirection is repeated until another kind of specification is found. This allows you to inherit the specification from another macro. a list The elements of the list describe the types of the arguments of a calling form. The possible elements of a specification list are described in the following sections. * Menu: * Specification List:: How to specify complex patterns of evaluation. * Backtracking:: What Edebug does when matching fails. * Specification Examples:: To help understand specifications.