-@node The Debugger
+@node Debugger
@comment node-name, next, previous, up
-@chapter The Debugger
+@chapter Debugger
@cindex Debugger
The SBCL debugger (as the CMUCL debugger it was derived from) has very
* Exiting Commands::
* Information Commands::
* Function Tracing::
+* Single Stepping::
@end menu
@node Starting the Debugger
@item
the debugger is explicitly entered with the Lisp @code{break} or
-@code{debug} functions.
+@code{invoke-debugger} functions.
@end itemize
top-level. After printing its banner, the debugger prints the current
frame and the debugger prompt.
+When the debugger is invoked by a condition, ANSI mandates that the
+value of @code{*debugger-hook*}, if any, be called with two arguments:
+the condition that caused the debugger to be invoked and the previous
+value of @code{*debugger-hook*}. When this happens,
+@code{*debugger-hook*} is bound to NIL to prevent recursive
+errors. However, ANSI also mandates that @code{*debugger-hook*} not be
+invoked when the debugger is to be entered by the @code{break}
+function. For users who wish to provide an alternate debugger
+interface (and thus catch @code{break} entries into the debugger),
+SBCL provides @code{sb-ext:*invoke-debugger-hook*}, which is invoked
+during any entry into the debugger.
+
+@include var-sb-ext-star-invoke-debugger-hook-star.texinfo
+
@node The Debugger Command Loop
@comment node-name, next, previous, up
abbreviated by any unambiguous prefix: @command{help} can be typed as
@samp{h}, @samp{he}, etc. For convenience, some commands have
ambiguous one-letter abbreviations: @samp{f} for @command{frame}.
+@comment FIXME: what does that last bit mean?
The package is not significant in debugger commands; any symbol with the
name of a debugger command will work. If you want to show the value of
In the debugger, it is possible to override the printing behaviour of
the REPL.
-@defvr {Variable} *debug-print-variable-alist*
+@defvr {Variable} sb-debug:*debug-print-variable-alist*
An association list describing new bindings for special variables
(typically *PRINT-FOO* variables) to be used within the debugger, e.g.
@itemize
@item
-@dfn{Variables} (@pxref{Variable Access}), which are the values being operated
-on, and
+@dfn{variables} (@pxref{Variable Access}), which are the values being operated
+on;
@item
-@dfn{Arguments} to the call (which are really just particularly
+@dfn{arguments} to the call (which are really just particularly
interesting variables), and
@item
-A current location (@pxref{Source Location Printing}), which is the place in
+a current location (@pxref{Source Location Printing}), which is the place in
the program where the function was running when it stopped to call
another function, or because of an interrupt or error.
then @samp{#<unavailable-arg>} will be printed instead of the argument
value.
+@vindex *debug-print-variable-alist*
Printing of argument values is controlled by
@code{*debug-print-variable-alist*}. @xref{Controlling Printing in
the Debugger}.
information, and lifetime information that tells the debugger when
arguments are available (even when @code{speed} is @code{3} or the
argument is set).
-
+
@item > 2
Any level greater than @code{2} gives level @code{2} and in addition
disables tail-call optimization, so that the backtrace will contain
the command @command{return} can be used to continue execution by
returning a value from the current stack frame.
+If @code{debug} is also at least 2, then the code is @emph{partially
+steppable}. If @code{debug} is 3, the code is @emph{fully steppable}.
+@xref{Single Stepping} for details.
+
@end table
As you can see, if the @code{speed} quality is @code{3}, debugger performance is
@var{n} frames if specified. The printing is controlled by @code{*debug-print-variable-alist*}.
@end deffn
-@comment FIXME (rudi 2004-03-31): sbcl doesn't support breakpoints
-@comment and stepping as of version 0.8.9. The `list-locations'
-@comment command works, but executing a function leads to an error
-@comment when a breakpoint is hit. When stepping works, the
-@comment commented-out section below should be reinstated and the
-@comment example output updated to correspont to sbcl's behaviour.
+@deffn {Debugger Command} step
+Selects the @code{continue} restart if one exists and starts single stepping.
+@xref{Single Stepping}.
+@end deffn
+
+@c The new instrumentation based single stepper doesn't support
+@c the following commands, but BREAKPOINT at least should be
+@c resurrectable via (TRACE FOO :BREAK T).
-@c @node Breakpoint Commands, , Information Commands, The Debugger
-@c @comment node-name, next, previous, up
-@c @section Breakpoint Commands
@c @cindex Breakpoints
@c SBCL supports setting of breakpoints inside compiled functions and
@c is specified, delete all breakpoints.
@c @end deffn
-@c @deffn {Debugger Command} step
-@c Step to the next possible breakpoint location in the current function.
-@c This always steps over function calls, instead of stepping into them.
-@c @end deffn
-
-
@c @menu
@c * Breakpoint Example::
@c @end menu
@comment 0.8.9) in a state of flux. When it's sorted out, revive the
@comment cmucl documentation.
+@node Single Stepping
+@comment node-name, next, previous, up
+@section Single Stepping
+@cindex Stepper
+@cindex Single Stepping
+
+SBCL includes an instrumentation based single-stepper for compiled
+code, that can be invoked via the @code{step} macro, or from within
+the debugger. @xref{Debugger Policy Control} for details on enabling
+stepping for compiled code.
+
+Compiled code can be unsteppable, partially steppable, or fully steppable.
+
+@table @strong
+@item Unsteppable
+Single stepping is not possible.
+
+@item Partially steppable
+Single stepping is possible at sequential function call granularity:
+nested function calls cannot be stepped into, and no intermediate
+values are available.
+
+@item Fully steppable
+Single stepping is possible at individual function call argument
+granularity, nested calls can be stepped into, and intermediate values
+are available.
+
+@end table
+@include macro-common-lisp-step.texinfo
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