[IronPython] Debugging support PythonEngine

Kristof Wagemans kristof.wagemans at gmail.com
Sat Aug 12 10:38:01 CEST 2006

Thanks for the info. It's good to hear that there will be improvement
possible in this area in the future. Although, the way I interpret your
explanation, it's not going to be anytime soon (or even this year), because
you need enhancements to the underlying platform to make this possible.


I've experimented a bit with System.Diagnostics.DebuggerNonUserCodeAttribute
to see if it wasn't possible to skip stepping into IronPython code.
Unfortunately, the point where I get stuck in the assembly instructions is
in generated code. I don't understand this part of the code well enough to
know if it's possible to make the debugger skip these lines. Maybe this is
why you need the changes to the platform?


From: users-bounces at lists.ironpython.com
[mailto:users-bounces at lists.ironpython.com] On Behalf Of Shri Borde
Sent: Friday 11 August 2006 21:04
To: Discussion of IronPython
Subject: Re: [IronPython] Debugging support PythonEngine


Yes, we will definitely be working on improving the debugging support as it
is a critical part of the development process.  However, full support will
need work in all parts of the tool chain including VS.


Python local variables are implemented as normal MSIL variables (except in
cases like closures). Hence, VS is able to display them.


Currently, the best way to debug Python functions in VS while using
PythonEngine would be to enable EngineOptions.ClrDebuggingEnable, open the
PY file in VS and put a breakpoint where you want. Stepping in and out of
Python functions will step you through methods in IronPython.dll .


From: users-bounces at lists.ironpython.com
[mailto:users-bounces at lists.ironpython.com] On Behalf Of Kristof Wagemans
Sent: Friday, August 11, 2006 12:36 AM
To: 'Discussion of IronPython'
Subject: Re: [IronPython] Debugging support PythonEngine


Are there plans to improve the debugging experience in the future or are you
at a point where it is "as good as it gets"? Being able to debug makes
writing and using python scripts a lot easier.

Inside functions I can see not only the function parameters but also the
newly defined local variables. Are these different from the global
variables? I would have expected that the function locals are also stored
inside a dictionary.

Is it possible to step into python functions without getting into assembly
instructions? This is very frustrating and degrades the debugging experience
a lot. This is the more important issue for me. I'm not going to be using
global variables frequently, but mostly functions loaded in the PythonEngine
that are called from C#.



From: users-bounces at lists.ironpython.com
[mailto:users-bounces at lists.ironpython.com] On Behalf Of Shri Borde
Sent: Friday 11 August 2006 0:30
To: Discussion of IronPython
Cc: Glenn Hackney
Subject: Re: [IronPython] Debugging support PythonEngine


If EngineOptions.ClrDebuggingEnabled is set, we use AssemblyBuilder,
TypeBuilder, etc for PythonEngine.Executed. The code generated by
AssemblyBuilder, TypeBuilder, etc supports PDB debug information tracking
for the methods, and so you will be able to set breakpoints in the code.
However, it does not guarantee a perfect debugging experience.
PythonEngine.ExecuteFile will use a dictionary for storing global variables,
and these will not be visible because VS does not know about the dictionary.
If you use PythonEngine.CreateOptimizedModule, most global variables are
implemented using CLR statics, and so VS may be able to display them for
you. Global variables added using an exec statement will still not be


If EngineOptions.ClrDebuggingEnabled is false, we will use
System.Reflection.Emit.DynamicMethod. This does not support debug
information tracking at all, and you will not even be able to see function


So If EngineOptions.ClrDebuggingEnabled is will improve your debugging
experience, but it wont give you a perfect experience.



0-45DF-8B78-DC1B43134038>  you want to help develop Dynamic languages on

From: users-bounces at lists.ironpython.com
[mailto:users-bounces at lists.ironpython.com] On Behalf Of Kristof Wagemans
Sent: Thursday, August 10, 2006 2:10 PM
To: Discussion of IronPython
Subject: [IronPython] Debugging support PythonEngine


I have been experimenting with the debugging support for the PythonEngine.
When I use the following code I have several problems.


PythonEngine _pe;

EngineOptions options = new EngineOptions();

options.ClrDebuggingEnabled = true;

_pe = new PythonEngine(options);

_pe.ExecuteFile(@"  <script>  ");


Test script:


x = 1

y = 2


def Add(a, b):

    return a + b


z = Add(x, y)

print z



I opened the script file in Visual Studio and placed a breakpoint at the
beginning of the file. The application runs and breaks at the correct
location. Stepping through the lines works, but I cannot see any values of
the global variables.

When I try to step into the function I get a notification that there is no
source code available and I must show the disassembly. After I step several
times through the assembly instructions I can return to the original source
code. Inside the function I can see the values of the function variables.

I have tried debugging ipy.exe with the script and there I can see the
global variables, but I still have the problem with stepping into a
function. In ipy.exe the script file is executed in a different way. Using
the same method I can also see the global variables with my PythonEngine
instance. I apparently don't need to set ClrDebuggingEnabled in this case.


PythonEngine _pe;

_pe = new PythonEngine();

OptimizedEngineModule engineModule = _pe.CreateOptimizedModule(@"  <script>
", "__main__", true);



Are you required to use an OptimizedEngineModule to be able to debug
completely? Am I forgetting some settings for debugging? Can I step directly
into a function without getting into the assembly instructions?


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