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authorRichard M. Stallman <rms@gnu.org>1994-04-30 02:19:25 +0000
committerRichard M. Stallman <rms@gnu.org>1994-04-30 02:19:25 +0000
commitae4a385754aa0ab07c9aad929fc87c49c9c07cc6 (patch)
treefbc0402f6e2dce0da1e1732d09ca165f637bc9d5 /lispref/debugging.texi
parentb5b911f995d9c92df4a7518bd7b06504889d82ed (diff)
*** empty log message ***
Diffstat (limited to 'lispref/debugging.texi')
-rw-r--r--lispref/debugging.texi102
1 files changed, 54 insertions, 48 deletions
diff --git a/lispref/debugging.texi b/lispref/debugging.texi
index b16c5407c9..5b4905c30a 100644
--- a/lispref/debugging.texi
+++ b/lispref/debugging.texi
@@ -81,7 +81,7 @@ debugger each time this happens. If you want errors to enter the
debugger, set the variable @code{debug-on-error} to non-@code{nil}.
@defopt debug-on-error
-This variable determines whether the debugger is called when a error is
+This variable determines whether the debugger is called when an error is
signaled and not handled. If @code{debug-on-error} is @code{t}, all
errors call the debugger. If it is @code{nil}, none call the debugger.
@@ -93,13 +93,15 @@ value invoke the debugger.
To debug an error that happens during loading of the @file{.emacs}
file, use the option @samp{-debug-init}, which binds
-@code{debug-on-error} to @code{t} while @file{.emacs} is loaded.
+@code{debug-on-error} to @code{t} while @file{.emacs} is loaded and
+inhibits use of @code{condition-case} to catch init file errors.
- If your @file{.emacs} file sets @code{debug-on-error}, the effect
-lasts only until the end of loading @file{.emacs}. (This is an
-undesirable by-product of the @samp{-debug-init} feature.) If you want
-@file{.emacs} to set @code{debug-on-error} permanently, use
-@code{after-init-hook}, like this:
+ If your @file{.emacs} file sets @code{debug-on-error}, the effect may
+not last past the end of loading @file{.emacs}. (This is an undesirable
+byproduct of the code that implements the @samp{-debug-init} command
+line option.) The best way to make @file{.emacs} set
+@code{debug-on-error} permanently is with @code{after-init-hook}, like
+this:
@example
(add-hook 'after-init-hook
@@ -121,8 +123,8 @@ with @kbd{C-g}, which causes quit.
looping. To get more information, you can set the variable
@code{debug-on-quit} to non-@code{nil}. Quitting with @kbd{C-g} is not
considered an error, and @code{debug-on-error} has no effect on the
-handling of @kbd{C-g}. Contrariwise, @code{debug-on-quit} has no effect
-on errors.@refill
+handling of @kbd{C-g}. Likewise, @code{debug-on-quit} has no effect on
+errors.
Once you have the debugger running in the middle of the infinite loop,
you can proceed from the debugger using the stepping commands. If you
@@ -184,7 +186,6 @@ on it, the code to enter the debugger is lost.
@end group
@group
(fact 3)
- @result{} 6
@end group
@group
@@ -230,9 +231,9 @@ before you save the file!
The place where you insert @samp{(debug)} must be a place where an
additional form can be evaluated and its value ignored. (If the value
-isn't ignored, it will alter the execution of the program!) The most
-common suitable places are inside a @code{progn} or an implicit
-@code{progn} (@pxref{Sequencing}).
+of @code{(debug)} isn't ignored, it will alter the execution of the
+program!) The most common suitable places are inside a @code{progn} or
+an implicit @code{progn} (@pxref{Sequencing}).
@node Using Debugger
@subsection Using the Debugger
@@ -257,12 +258,12 @@ the debugger gets out of the recursive edit and kills the backtrace
buffer.
@cindex current stack frame
- The contents of the backtrace buffer show you the functions that are
-executing and their argument values. It also allows you to specify a
-stack frame by moving point to the line describing that frame. (A stack
-frame is the place where the Lisp interpreter records information about
-a particular invocation of a function.) The frame whose line point is
-on is considered the @dfn{current frame}. Some of the debugger commands
+ The backtrace buffer shows you the functions that are executing and
+their argument values. It also allows you to specify a stack frame by
+moving point to the line describing that frame. (A stack frame is the
+place where the Lisp interpreter records information about a particular
+invocation of a function.) The frame whose line point is on is
+considered the @dfn{current frame}. Some of the debugger commands
operate on the current frame.
The debugger itself must be run byte-compiled, since it makes
@@ -342,10 +343,12 @@ to quit, and not debug, use the @kbd{q} command.
Return a value from the debugger. The value is computed by reading an
expression with the minibuffer and evaluating it.
-The @kbd{r} command makes a difference when the debugger was invoked due
-to exit from a Lisp call frame (as requested with @kbd{b}); then the
-value specified in the @kbd{r} command is used as the value of that
-frame.
+The @kbd{r} command is useful when the debugger was invoked due to exit
+from a Lisp call frame (as requested with @kbd{b}); then the value
+specified in the @kbd{r} command is used as the value of that frame. It
+is also useful if you call @code{debug} and use its return value.
+Otherwise, @kbd{r} has the same effect as @kbd{c}, and the specified
+return value does not matter.
You can't use @kbd{r} when the debugger was entered due to an error.
@end table
@@ -369,7 +372,7 @@ whatever called @code{debug}. This is the only way the function
If the first of the @var{debugger-args} passed to @code{debug} is
@code{nil} (or if it is not one of the special values in the table
-below), then @code{debeg} displays the rest of its arguments at the the
+below), then @code{debug} displays the rest of its arguments at the the
top of the @samp{*Backtrace*} buffer. This mechanism is used to display
a message to the user.
@@ -447,8 +450,6 @@ under which @code{debug} is called.
@end table
@end defun
-@need 5000
-
@node Internals of Debugger
@subsection Internals of the Debugger
@@ -550,12 +551,12 @@ The @kbd{d} command in the debugger works by setting this variable.
@defun backtrace-debug level flag
This function sets the debug-on-exit flag of the stack frame @var{level}
-levels, giving it the value @var{flag}. If @var{flag} is
+levels down the stack, giving it the value @var{flag}. If @var{flag} is
non-@code{nil}, this will cause the debugger to be entered when that
frame later exits. Even a nonlocal exit through that frame will enter
the debugger.
-Normally, this function is only called by the debugger.
+This function is used only by the debugger.
@end defun
@defvar command-debug-status
@@ -564,9 +565,9 @@ command. Each time a command is called interactively, this variable is
bound to @code{nil}. The debugger can set this variable to leave
information for future debugger invocations during the same command.
-The advantage of using this variable rather that defining another global
-variable is that the data will never carry over to a subsequent command
-invocation.
+The advantage, for the debugger, of using this variable rather than
+another global variable is that the data will never carry over to a
+subsequent command invocation.
@end defvar
@defun backtrace-frame frame-number
@@ -581,12 +582,12 @@ If that frame has evaluated its arguments and called its function
already, the value is @code{(t @var{function}
@var{arg-values}@dots{})}.
-In the return value, @var{function} is whatever was supplied as @sc{car}
-of evaluated list, or a @code{lambda} expression in the case of a macro
-call. If the function has a @code{&rest} argument, that is represented
-as the tail of the list @var{arg-values}.
+In the return value, @var{function} is whatever was supplied as the
+@sc{car} of the evaluated list, or a @code{lambda} expression in the
+case of a macro call. If the function has a @code{&rest} argument, that
+is represented as the tail of the list @var{arg-values}.
-If the argument is out of range, @code{backtrace-frame} returns
+If @var{frame-number} is out of range, @code{backtrace-frame} returns
@code{nil}.
@end defun
@@ -643,8 +644,8 @@ Usually all the lines from a certain point to the end of the function
will shift to the right. There is probably a missing close parenthesis,
or a superfluous open parenthesis, near that point. (However, don't
assume this is true; study the code to make sure.) Once you have found
-the discrepancy, undo the @kbd{C-M-q}, since the old indentation is
-probably appropriate to the intended parentheses.
+the discrepancy, undo the @kbd{C-M-q} with @kbd{C-_}, since the old
+indentation is probably appropriate to the intended parentheses.
After you think you have fixed the problem, use @kbd{C-M-q} again. If
the old indentation actually fit the intended nesting of parentheses,
@@ -654,11 +655,11 @@ anything.
@node Excess Close
@subsection Excess Close Parentheses
- To deal with an excess close parenthesis, first insert an
-open parenthesis at the beginning of the file and type @kbd{C-M-f} to
-find the end of the unbalanced defun. (Then type @kbd{C-@key{SPC} C-_
-C-u C-@key{SPC}} to set the mark there, undo the insertion of the
-open parenthesis, and finally return to the mark.)
+ To deal with an excess close parenthesis, first insert an open
+parenthesis at the beginning of the file, back up over it, and type
+@kbd{C-M-f} to find the end of the unbalanced defun. (Then type
+@kbd{C-@key{SPC} C-_ C-u C-@key{SPC}} to set the mark there, undo the
+insertion of the open parenthesis, and finally return to the mark.)
Then find the actual matching close parenthesis by typing @kbd{C-M-f}
at the beginning of the defun. This will leave you somewhere short of
@@ -670,10 +671,15 @@ type @kbd{C-M-q} at the beginning of the defun. A range of lines will
probably shift left; if so, the missing open parenthesis or spurious
close parenthesis is probably near the first of those lines. (However,
don't assume this is true; study the code to make sure.) Once you have
-found the discrepancy, undo the @kbd{C-M-q}, since the old indentation
-is probably appropriate to the intended parentheses.
+found the discrepancy, undo the @kbd{C-M-q} with @kbd{C-_}, since the
+old indentation is probably appropriate to the intended parentheses.
+
+ After you think you have fixed the problem, use @kbd{C-M-q} again. If
+the old indentation actually fit the intended nesting of parentheses,
+and you have put back those parentheses, @kbd{C-M-q} should not change
+anything.
-@node Compilation Errors
+@node Compilation Errors, Edebug, Syntax Errors, Debugging
@section Debugging Problems in Compilation
When an error happens during byte compilation, it is normally due to
@@ -695,7 +701,7 @@ the error.
If the error was detected while compiling a form that had been read
successfully, then point is located at the end of the form. In this
-case, it can't localize the error precisely, but can still show you
-which function to check.
+case, this technique can't localize the error precisely, but can still
+show you which function to check.
@include edebug.texi