We help IT Professionals succeed at work.
Get Started
Troubleshooting Question

COM Interop, pure function call on exit

Last Modified: 2020-10-31
A program written by another company allows for add-ins to be written which communicate via COM interop.

Their program appears to be written in C++, and uses managed code according to Process Explorer.

Our Add-In is written in C#. We compile and register our Add-In as a COM object during compile with Visual Studio.

We found their program will crash on exit with a Pure Function Call error when our Add-In is used.

However, the program will NOT crash if we call Marshal.ReleaseComObject() on every object, and then in the OnDisconnect() method we call GC.Collect(); followed by GC.WaitForPendingFinalizers().

I'm trying to understand why this is.

I did find one comment:

"A common approach for releasing unmanaged objects is to set the RCW reference to null, and call System.GC.Collect followed by System.GC.WaitForPendingFinalizers."

Why would this be necessary to prevent a Pure Function Call error on exit?

Examining the call stack of the crash shows it's attempting to perform some sort of RCW release when it encounters the crash.
Watch Question
Top Expert 2015
This problem has been solved!
Unlock 1 Answer and 1 Comment.
See Answer
Why Experts Exchange?

Experts Exchange always has the answer, or at the least points me in the correct direction! It is like having another employee that is extremely experienced.

Jim Murphy
Programmer at Smart IT Solutions

When asked, what has been your best career decision?

Deciding to stick with EE.

Mohamed Asif
Technical Department Head

Being involved with EE helped me to grow personally and professionally.

Carl Webster
CTP, Sr Infrastructure Consultant

An Experts Exchange subscription includes unlimited access to online courses.

Get Started
Ask ANY Question

Connect with Certified Experts to gain insight and support on specific technology challenges including:

  • Troubleshooting
  • Research
  • Professional Opinions
Did You Know?

We've partnered with two important charities to provide clean water and computer science education to those who need it most. READ MORE