[Mono-list] Managed C++ assemblies and Mono

Patrick Hartling patrick@vrac.iastate.edu
Fri, 10 Jan 2003 16:31:09 -0600

Jason Whittington wrote:
>>I would agree that for a native C interface (e.g., GTK+), that would
> be
>>better.  From what I have seen of P/Invoke, however, it seems
> undesirable
>>for use with a C++ API due to all the static methods.  
> There's really no other practical way to do interop. This is due to a
> weakness in C++, not a weakness in .NET.  C++ was written with
> source-code compatibility in mind, not binary compatibility.  As a
> result, C++ compilers are free to handle virtual dispatch and name
> mangling however they like, making binary interop infeasible. 
> As for your desire that things be more OO in nature, get over it :).

Would that I could, but that's not an option.  I have 500,000+ lines of 
extant C++ code representing 6 years of work that I cannot rewrite to be 
less object oriented.

> P/Invoke is actually way nicer to work with than, say, JNI.  Similar
> issues.

That is very true.  I tried JNI for a different project a while ago, and 
it hurt.  P/Invoke is leaps and bounds better.

>> What it really
>>comes down to is that I want to write a class in C# that implements an
>>interface defined in unmanaged C++.  An instance of the C# class would
> be
>>passed through to unmanaged C++ code.  There are a lot of details
>>involved with this, but the inherent object-oriented nature does not
> seem
>>to lend itself well to the structure of P/Invoke-style code.
> Easier to say than to actually do. For this to work the runtime and the
> C++ compiler would have to agree on a tightly-specified binary interface
> contract. This has been done before; it was called COM (XPCOM on
> Linux)[1]. COM interop is even more complex than P/Invoke, especially
> when you start passing interface references around instead of flat data
> structures.  Lifetime management and managed/unmanaged interaction turns
> into a horrible sticky quagmire. Check out Adam Nathan's book[2] or Sam
> Gentile's website [3] for more discussion.

Thanks for the references.  Anything to help me in this quagmire is much 
appreciated.  :)


> Jason
> [1]See Chapter 1 of "Essential COM" "COM as a better C++"
> [2] ".NET and COM: The Complete Interopability guide"
> http://www.amazon.com/exec/obidos/tg/detail/-/0672321432/qid=1042230082/
> sr=8-5/ref=sr_8_5/104-6049141-7111136?v=glance&s=books&n=507846
> [3] http://radio.weblogs.com/0105852/
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Patrick L. Hartling                     | Research Assistant, VRAC
patrick@vrac.iastate.edu                | 2624 Howe Hall: 1.515.294.4916
http://www.137.org/patrick/             | http://www.vrac.iastate.edu/