Environment

• Pythonnet version: 2.5.2
• Python version: issue verified on 3.7.2, 3.7.7 and 3.8.6
• Operating System: Windows 10 64bit
• .NET Runtime: .NET Framework 4.7.2

Details

Hello everybody and thanks for this great piece of Software!

The basic issue is:

• if I throw a .NET exception from within C# code
• and the exception moves into the python space
  • i.e. the C# method was called from python
• then the memory of the exception does not get released anymore

This becomes apparent when you throw quite a lot of exceptions and your applications runs 24/7.

Reproducability

The issue is fairly easy to reproduce. I have also setup a sample repository, which reproduces the issue.

https://github.com/Rookfighter/pythonnet-memleak-exceptions

The basis instruction are:

• setup a Visual Studio Project of the type "Class Library .NET Framework 4.7.2"
• create aExceptionThrower class

usingSystem;namespaceLeakingExceptions{publicclassExceptionThrower{publicvoidThrowException(){thrownewException("a simple exception");}}}

• create a python script which imports the assembly
• create aExceptionThrower object and callThrowException within a loopedtry except block

importosimport__main__importclr# bin dir must be adjusted to your relative path!bin_dir=os.path.abspath(os.path.join(os.path.dirname(__main__.__file__),'../Source/LeakingExceptions/bin/Debug'))clr.AddReference(os.path.join(bin_dir,'LeakingExceptions'))fromLeakingExceptionsimportExceptionThrowerthrower=ExceptionThrower()whileTrue:try:thrower.ThrowException()except:pass

• in the task manager you can then watch the application to accumulate memory and never release it