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The debugger is an interactive read-eval-print loop much like the normal
top-level, but some symbols are interpreted as debugger commands instead
of being evaluated. A debugger command starts with the symbol name of
the command, possibly followed by some arguments on the same line. Some
commands prompt for additional input. Debugger commands can be
abbreviated by any unambiguous prefix: help can be typed as
h, he, etc. For convenience, some commands have
ambiguous one-letter abbreviations: f for frame.
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
a variable that happens also to be the name of a debugger command, you
can use the list-locals command or the debug:var
function, or you can wrap the variable in a progn to hide it from
the command loop.
The debugger prompt is “frame]”, where frame is the number
of the current frame. Frames are numbered starting from zero at the top (most
recent call), increasing down to the bottom. The current frame is the frame
that commands refer to. The current frame also provides the lexical
environment for evaluation of non-command forms.
The debugger evaluates forms in the lexical
environment of the functions being debugged. The debugger can only
access variables. You can’t go or return-from into a
function, and you can’t call local functions. Special variable
references are evaluated with their current value (the innermost binding
around the debugger invocation)—you don’t get the value that the
special had in the current frame. See debug-vars for more
information on debugger variable access.
Next: Stack Frames, Previous: Debugger Introduction, Up: The Debugger [Contents][Index]