Mathics3 Debugger Module

Until we have some proper documentation here are some examples.

Mathics3 Module Examples

To enable debugging in Mathics3, install mathics3-debugger. Inside a mathics3 session run:

In[1]:= LoadModule["pymathics.debugger"]
Out[1]= "pymathics.debugger"

Next, you need to active some events to trigger going into the debugger:

In[2]:= DebugActivate[mpmath->True]
Out[2]=

Other events include: "Debugger", "Get", "Numpy", "SymPy", "apply", and "evalMethd".

In the above, mpmath->True goes into the debugger anytime a mpmath function is called. Exp[1.0] is such a function:

In[3]:= Exp[1.0]
mpmath call  : mpmath.ctx_base.StandardBaseContext.power(2.718281828459045, 1.0)
(/tmp/mathics-core/mathics/eval/arithmetic.py:68 @88): run_mpmath
mp 68             result_mp = tracing.run_mpmath(mpmath_function, *mpmath_args)
(Mathics3 Debug)

A useful command to run is bt -b which shows the Buitin Function calls in the call stack:

(Mathics3 Debug) bt -b
B#0 (2) Power[z__]
          called from file '/tmp/mathics-core/mathics/core/builtin.py' at line 659
B#1 (3) Power[x_, y_]
          called from file '/tmp/mathics-core/mathics/builtin/arithfns/basic.py' at line 477

To get a list of all debugger commands:

(Mathics3 Debug) help *
List of all debugger commands:
    alias      down   help  mathics3      reload  trepan3k
    backtrace  eval   info  printelement  set     up
    continue   frame  kill  python        show

When you are done inspecting things, run continue (or short-hand c) to resume execution:

(Mathics3 Debug) c
mpmath result: 2.71828182845905
Out[3]= 2.71828

Post-mortem debugging

To enter the debugger on an unrecoverable error, use the --post-mortem option when invoking mathics:

mathics --post-mortem
# Find a Python bug in Mathics3 and trigger that.
# I modified Compress.eval() and added 1/0

In[1]:= Compress["abc"]
  Traceback (most recent call last):
  File "/tmp/mathicsscript", line 8, in <module>
  sys.exit(main())
           ^^^^^
  ...
  ZeroDivisionError: division by zero
  Uncaught exception. Entering post-mortem debugger...
  (/tmp/mathics/builtin/compress.py:37 @6): eval
  !! 37         1/0
  R=> (<class 'ZeroDivisionError'>, ZeroDivisionError('division by zero'),
  (Trepan3k:pm) load trepan3k_mathics3
  loaded command: "mathics3"
  loaded command: "mbacktrace"
  loaded command: "mup"
  loaded command: "printelement"
  (Trepan3k:pm) mbt -b
  B>0 (0) Compress[expr_, OptionsPattern[Compress]]
            called from file '/src/external-vcs/github/Mathics3/mathics-core/mathics/builtin/compress.py' at line 37
  B>1 (36) Compress[expr_, OptionsPattern[Compress]]
             called from file '/src/external-vcs/github/Mathics3/mathics-core/mathics/builtin/compress.py' at line 37
  (Trepan3k:pm)