Managed/Native Debugging in C#/C++

I had a problem debugging my solution consisting of C#, C++/CLI, and native C++ projects. I was not able to get breakpoints working in the native C++ parts – after running the solution with breakpoints set, they were turning gray with warning sign, and their tooltip stated that “The breakpoint will not currently be hit. No symbols have been loaded for this document.” despite all debug properties were set right on those projects and all debugging symbols existed. After fighting it for a few hours and almost giving up, I started to think that the problem might not be with the native C++ projects, but rather somewhere else, e.g. in the StartUp project, which is C#. Checked that project’s properties, and guess what! Debug > Enable unmanged code debugging option was off!!! Switched it on, and voila – breakpoints work fine in native C++ DLL now!!! :)

Exceptions in C++

In Google C++ Style Guide they state that they are not using exceptions in C++ code at Google. They have reasons for it (“historical” mostly, as usual), but I do not necessarily agree with their view on it. Anyway, exceptions are quite a controversial topic in C++ community, and a must-read C++ Exceptions: Pros and Cons article at CodeProject goes deeper into the subject.

Personally I think that exceptions are really great, although I see how people can get things messy/wrong when using exceptions in inappropriate contexts and/or in inappropriate ways. Recipe to avoid problems? My own short list:

• Use exceptions when they are really needed, i.e. when something exceptional happened
• Understand Exception guarantees AKA Abrahams guarantees (see more at Exception-Safety in Generic Components – Lessons Learned from Specifying Exception-Safety for the C++ Standard Library by David Abrahams)
• Follow Resource Acquisition Is Initialization AKA Resource Initialization Is Acquisition (or RAII/RIIA in short) principle

Problem with C++/CLI + ATL Combo

Exactly… Wanted to use ATL (for CComPtr class and some other things) in my C++/CLI project (VS2008 with or without SP1) and… got nice assert on _CrtIsValidHeapPointer(pUserData) in dbgheap.c. Cool! Exactly that was missing to make my day better!

Some investigation, and I had answer to my problem. Actually two answers. Both pretty simple:

1. As I had /NOENTRY specified in the No Entry Point item in the Linker/Advanced section of the project settings, I could add __DllMainCRTStartup@12 to the Force Symbol References item in the Linker/Input section of the project settings
2. Alternatively, I could set No Entry Point item in the Linker/Advanced section of the project settings to No (as I said, I had /NOENTRY there)

I have tried both solutions, and both worked; I settled on the latter as more intuitive and clean. Always live, always learn…

marshal_as String Arrays

Giovanni Dicanio developed an extension (template specialization) to marshal_as<> library of Visual C++ 2008, to convert Unicode string arrays between managed (CLR) and native (STL/C++) code. The code is available at marshal_as String Arrays.

Arrays in C++/CLI

Nishant Sivakumar has pretty deep introduction of C++/CLI arrays (see also his blog for more interesting stuff about mainly C++/CLI).