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96 lines
3.3 KiB
Plaintext
96 lines
3.3 KiB
Plaintext
Debugging in ULisp KMP 25 April 80
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------------------------------------------------------------------------------
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Break Loops
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A Breakloop is just like the toplevel evaluation loop except it is a temporary
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interruption of the evaluation of some other form, and as such occurs in a
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context where some bindings from that evaluation may have taken place.
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Breakloops may be unconditionally invoked from code by
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(break) or (break evaluated-message)
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or they may be conditionally invoked by
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(break evaluated-message evaluated-condition)
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where if the evaluated-condition returns non-(), then the break will occur.
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The function recover will become defined in a breakloop and can be used to
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return from a breakpoint. With no args, it simply returns (value undefined),
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or with one argument it will return that value. #### It may be that
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recover will not always work. This is a known bug which will hopefully be
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fixed soon. Report instances of it to speed service. ####
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When in a breakloop. You will see a prompt like:
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[Break Level n]
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Lisp->
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unless you do (prompt nil), which will of course suppress all prompting.
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------------------------------------------------------------------------------
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Debug
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Debug is a system-provided stack-debugger. It can be used to explicitly
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invoke the debugger from a breakpoint by typing (debug) or it can be caused
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to activate automatically on an error by doing (backtrace debug). Disabling
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of this feature is by (backtrace nodebug).
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Debug commands are one character. The following commands are available:
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? Gives short help description.
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H Offers to document one or all commands.
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. Type out current stack frame in abbreviated form.
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T Type out current stack frame in normal form, no abbreviation.
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P Type out current stack frame in pretty-printed form, no abbreviation.
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F Displays all stack frames in abbreviated form.
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A Goes to top of stack
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U Goes up a stack frame.
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D Goes down a stack frame.
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Z Goes to bottom of stack
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B Gives a breakpoint at current stack frame level.
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C Continues from current stack frame by re-evaluating that form.
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(Presumably this should be done if you have first done a "B"
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and corrected the error or if the error was caused by external
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conditions such as the file system which have since been cleared.)
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R Returns from the current stack frame by reading an expression from the
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terminal and returning the value returned by that expression rather
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than anything to do with the frame which had initially been at the
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current form on the stack...
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Q Quits the debugger. If invoked from the error handler, control returns
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to the next higher breakpoint or toplevel read-eval-print loop.
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If invoked from (debug), then returns from that invocation.
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------------------------------------------------------------------------------
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Quit Characters
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#### These are likely to change in the very near future ####
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Currently Likely to Become Description
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--------- ---------------- -----------
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Control-B Control-G Quits to toplevel
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Control-X Control-X Error, or local, quit
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none Control-B Runs a break loop
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------------------------------------------------------------------------------
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Tracing
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#### No trace facility yet exists. One is planned ####
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------------------------------------------------------------------------------
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