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
.
Next: Keyword Commands, Up: Debugging [Contents][Index]