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• Source Level Debugging: | ||
• Keyword Commands: | ||
• Functions and Variables for Debugging: |
Next: Keyword Commands, Up: Debugging [Contents][Index]
Maxima has a built-in source level debugger. The user can set a breakpoint at a function, and then step line by line from there. The call stack may be examined, together with the variables bound at that level.
The command :help
or :h
shows the list of debugger commands.
(In general,
commands may be abbreviated if the abbreviation is unique. If not
unique, the alternatives will be listed.)
Within the debugger, the user can also use any ordinary Maxima
functions to examine, define, and manipulate variables and expressions.
A breakpoint is set by the :br
command at the Maxima prompt.
Within the debugger,
the user can advance one line at a time using the :n
(“next”) command.
The :bt
(“backtrace”) command shows a list of stack frames.
The :r
(“resume”) command exits the debugger and continues with
execution. These commands are demonstrated in the example below.
(%i1) load ("/tmp/foobar.mac"); (%o1) /tmp/foobar.mac (%i2) :br foo Turning on debugging debugmode(true) Bkpt 0 for foo (in /tmp/foobar.mac line 1) (%i2) bar (2,3); Bkpt 0:(foobar.mac 1) /tmp/foobar.mac:1:: (dbm:1) :bt <-- :bt typed here gives a backtrace #0: foo(y=5)(foobar.mac line 1) #1: bar(x=2,y=3)(foobar.mac line 9) (dbm:1) :n <-- Here type :n to advance line (foobar.mac 2) /tmp/foobar.mac:2:: (dbm:1) :n <-- Here type :n to advance line (foobar.mac 3) /tmp/foobar.mac:3:: (dbm:1) u; <-- Investigate value of u 28 (dbm:1) u: 33; <-- Change u to be 33 33 (dbm:1) :r <-- Type :r to resume the computation (%o2) 1094
The file /tmp/foobar.mac
is the following:
foo(y) := block ([u:y^2], u: u+3, u: u^2, u); bar(x,y) := ( x: x+2, y: y+2, x: foo(y), x+y);
USE OF THE DEBUGGER THROUGH EMACS
If the user is running the code under GNU emacs in a shell window (dbl shell), or is running the graphical interface version, Xmaxima, then if he stops at a break point, he will see his current position in the source file which will be displayed in the other half of the window, either highlighted in red, or with a little arrow pointing at the right line. He can advance single lines at a time by typing M-n (Alt-n).
Under Emacs you should run in a dbl
shell, which requires the
dbl.el
file in the elisp directory.
Make sure you install the elisp files or add the Maxima elisp directory to
your path:
e.g., add the following to your .emacs file or the site-init.el
(setq load-path (cons "/usr/share/maxima/5.9.1/emacs" load-path)) (autoload 'dbl "dbl")
then in emacs
M-x dbl
should start a shell window in which you can run programs, for example Maxima, gcl, gdb etc. This shell window also knows about source level debugging, and display of source code in the other window.
The user may set a break point at a certain line of the
file by typing C-x space
. This figures out which function
the cursor is in, and then it sees which line of that function
the cursor is on. If the cursor is on, say, line 2 of foo
, then it will
insert in the other window the command, “:br foo 2
”, to
break foo
at its second line. To have this enabled, the user must have
maxima-mode.el turned on in the window in which the file foobar.mac
is
visiting. There are additional commands available in that file window, such as
evaluating the function into the Maxima, by typing Alt-Control-x
.
Categories: Debugging
Next: Functions and Variables for Debugging, Previous: Source Level Debugging, Up: Debugging [Contents][Index]
Keyword commands are special keywords which are not interpreted as Maxima
expressions. A keyword command can be entered at the Maxima prompt or the
debugger prompt, although not at the break prompt.
Keyword commands start with a colon, ’:
’.
For example, to evaluate a Lisp form you
may type :lisp
followed by the form to be evaluated.
(%i1) :lisp (+ 2 3) 5
The number of arguments taken depends on the particular command. Also,
you need not type the whole command, just enough to be unique among
the break keywords. Thus :br
would suffice for :break
.
The keyword commands are listed below.
:break F n
Set a breakpoint in function F
at line offset n
from the beginning of the function.
If F
is given as a string, then it is assumed to be
a file, and n
is the offset from the beginning of the file.
The offset is optional. If not given, it is assumed to be zero
(first line of the function or file).
:bt
Print a backtrace of the stack frames
:continue
Continue the computation
:delete
Delete the specified breakpoints, or all if none are specified
:disable
Disable the specified breakpoints, or all if none are specified
:enable
Enable the specified breakpoints, or all if none are specified
:frame n
Print stack frame n
, or the current frame if none is specified
:help
Print help on a debugger command, or all commands if none is specified
:info
Print information about item
:lisp some-form
Evaluate some-form
as a Lisp form
:lisp-quiet some-form
Evaluate Lisp form some-form
without any output
:next
Like :step
, except :next
steps over function calls
:quit
Quit the current debugger level without completing the computation
:resume
Continue the computation
:step
Continue the computation until it reaches a new source line
:top
Return to the Maxima prompt (from any debugger level) without completing the computation
Categories: Debugging
Previous: Keyword Commands, Up: Debugging [Contents][Index]
Default value: false
When a Maxima error occurs, Maxima will start the debugger if debugmode
is true
. The user may enter commands to examine the call stack, set
breakpoints, step through Maxima code, and so on. See debugging
for a
list of debugger commands.
Enabling debugmode
will not catch Lisp errors.
Categories: Debugging Global flags
Default value: false
When refcheck
is true
, Maxima prints a message
each time a bound variable is used for the first time in a
computation.
Categories: Evaluation Console interaction Global flags
Default value: false
If setcheck
is set to a list of variables (which can
be subscripted),
Maxima prints a message whenever the variables, or
subscripted occurrences of them, are bound with the
ordinary assignment operator :
, the ::
assignment
operator, or function argument binding,
but not the function assignment :=
nor the macro assignment
::=
operators.
The message comprises the name of the variable and the
value it is bound to.
setcheck
may be set to all
or true
thereby
including all variables.
Each new assignment of setcheck
establishes a new list of variables to
check, and any variables previously assigned to setcheck
are forgotten.
The names assigned to setcheck
must be quoted if they would otherwise
evaluate to something other than themselves.
For example, if x
, y
, and z
are already bound, then enter
setcheck: ['x, 'y, 'z]$
to put them on the list of variables to check.
No printout is generated when a
variable on the setcheck
list is assigned to itself, e.g., X: 'X
.
Categories: Console interaction Global flags
Default value: false
When setcheckbreak
is true
,
Maxima will present a break prompt
whenever a variable on the setcheck
list is assigned a new value.
The break occurs before the assignment is carried out.
At this point, setval
holds the value to which the variable is
about to be assigned.
Hence, one may assign a different value by assigning to setval
.
Categories: Console interaction Global flags
Holds the value to which a variable is about to be set when
a setcheckbreak
occurs.
Hence, one may assign a different value by assigning to setval
.
See also setcheck
and setcheckbreak
.
Categories: Console interaction Global variables
Given functions f_1, …, f_n, timer
puts each one on the
list of functions for which timing statistics are collected.
timer(f)$ timer(g)$
puts f
and then g
onto the list;
the list accumulates from one call to the next.
timer(all)
puts all user-defined functions (as named by the global
variable functions
) on the list of timed functions.
With no arguments, timer
returns the list of timed functions.
Maxima records how much time is spent executing each function
on the list of timed functions.
timer_info
returns the timing statistics, including the
average time elapsed per function call, the number of calls, and the
total time elapsed.
untimer
removes functions from the list of timed functions.
timer
quotes its arguments.
f(x) := x^2$ g:f$ timer(g)$
does not put f
on the timer list.
If trace(f)
is in effect, then timer(f)
has no effect;
trace
and timer
cannot both be in effect at the same time.
See also timer_devalue
.
Categories: Debugging
Given functions f_1, …, f_n,
untimer
removes each function from the timer list.
With no arguments, untimer
removes all functions currently on the timer
list.
After untimer (f)
is executed, timer_info (f)
still returns
previously collected timing statistics,
although timer_info()
(with no arguments) does not
return information about any function not currently on the timer list.
timer (f)
resets all timing statistics to zero
and puts f
on the timer list again.
Categories: Debugging
Default value: false
When timer_devalue
is true
, Maxima subtracts from each timed
function the time spent in other timed functions. Otherwise, the time reported
for each function includes the time spent in other functions.
Note that time spent in untimed functions is not subtracted from the
total time.
See also timer
and timer_info
.
Categories: Debugging Global flags
Given functions f_1, ..., f_n, timer_info
returns a matrix
containing timing information for each function.
With no arguments, timer_info
returns timing information for
all functions currently on the timer list.
The matrix returned by timer_info
contains the function name,
time per function call, number of function calls, total time,
and gctime
, which meant "garbage collection time" in the original Macsyma
but is now always zero.
The data from which timer_info
constructs its return value
can also be obtained by the get
function:
get(f, 'calls); get(f, 'runtime); get(f, 'gctime);
See also timer
.
Categories: Debugging
Given functions f_1, …, f_n, trace
instructs Maxima to
print out debugging information whenever those functions are called.
trace(f)$ trace(g)$
puts f
and then g
onto the list of
functions to be traced; the list accumulates from one call to the next.
trace(all)
puts all user-defined functions (as named by the global
variable functions
) on the list of functions to be traced.
With no arguments,
trace
returns a list of all the functions currently being traced.
The untrace
function disables tracing.
See also trace_options
.
trace
quotes its arguments. Thus,
f(x) := x^2$ g:f$ trace(g)$
does not put f
on the trace list.
When a function is redefined, it is removed from the timer list.
Thus after timer(f)$ f(x) := x^2$
,
function f
is no longer on the timer list.
If timer (f)
is in effect, then trace (f)
has no effect;
trace
and timer
can’t both be in effect for the same function.
Categories: Debugging
Sets the trace options for function f.
Any previous options are superseded.
trace_options (f, ...)
has no effect unless trace (f)
is also called (either before or after trace_options
).
trace_options (f)
resets all options to their default values.
The option keywords are:
noprint
Do not print a message at function entry and exit.
break
Put a breakpoint before the function is entered,
and after the function is exited. See break
.
lisp_print
Display arguments and return values as Lisp objects.
info
Print -> true
at function entry and exit.
errorcatch
Catch errors, giving the option to signal an error,
retry the function call, or specify a return value.
Trace options are specified in two forms. The presence of the option
keyword alone puts the option into effect unconditionally.
(Note that option foo is not put into effect by specifying
foo: true
or a similar form; note also that keywords need not
be quoted.) Specifying the option keyword with a predicate
function makes the option conditional on the predicate.
The argument list to the predicate function is always
[level, direction, function, item]
where level
is the recursion
level for the function, direction
is either enter
or exit
,
function
is the name of the function, and item
is the argument
list (on entering) or the return value (on exiting).
Here is an example of unconditional trace options:
(%i1) ff(n) := if equal(n, 0) then 1 else n * ff(n - 1)$ (%i2) trace (ff)$ (%i3) trace_options (ff, lisp_print, break)$ (%i4) ff(3);
Here is the same function, with the break
option conditional
on a predicate:
(%i5) trace_options (ff, break(pp))$ (%i6) pp (level, direction, function, item) := block (print (item), return (function = 'ff and level = 3 and direction = exit))$ (%i7) ff(6);
Categories: Debugging
Given functions f_1, …, f_n,
untrace
disables tracing enabled by the trace
function.
With no arguments, untrace
disables tracing for all functions.
untrace
returns a list of the functions for which
it disabled tracing.
Categories: Debugging
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