The .NET Framework helps developer boost their productivity by giving them a set of tools and libraries they need to quickly start implementing the core of their software without loosing time on details. The idea behind the Common Language Infrastructure (CLI) is to allow programming languages to interoperate by sharing code through libraries.
To take advantage of these libraries, a lot of languages got their .NET implementation counterparts, with for example: IronPython, IronRuby, or IronScheme. See http://en.wikipedia.org/wiki/List_of_CLI_languages#CLI_languages for more implementations.
Most of these languages when interpreted are implemented in .NET languages and can easily interact with the underlying platform. For compiled languages they generate IL and the result is a .NET assembly.
In the same way you can dynamically load symbols from a shared library, there are times you would like to be able to interact with the .NET Framework from non .NET languages such as C, C++, Java, Perl or PHP.
Through a short series of articles I am going to show you how to achieve this goal and get the power of .NET in all your favorite languages in less than 500 lines of code.
Back to the origin…
Like for software components at a higher level, the best way to make programming languages interoperate with each other is to define some kind of interfaces. If we look what has been done in the past with native languages we can consider as part of this interface: the processor architecture and its instruction set, the binary format with the way symbols are exported, the type sizes and the conventions to call code.
Assuming that your binaries respect this same interface they can freely share symbols. We are going to respect this interface in order to build a bridge library between the native and the .NET worlds. This native library would be then accessible from non .NET languages.
Did I already tell you how much I like C++? (cf. http://blogs.msdn.com/b/doriancorompt/archive/2012/04/25/6-sequences-being-lazy-is-allowed.aspx)
But don’t worry I have good news for you, a nice version of C++ exists in this world! It is C++/CLI! As you probably guessed this version of C++ is targeting the Common Language Infrastructure. Besides the fact it fills some C++ lacks such as automatic memory management and boilerplate code generation for data member accessors, one of the good thing is that it provides you a seamless and simple way to mix native and managed code. Moreover once compiled the binary has both native and managed sections and can export native symbols such as functions using CLR objects.
As a solution for our problem I then suggests to use C++/CLI to build an interoperability DLL, whose functions are dynamically loadable by non .NET languages and which will allow us to use the .NET Framework.
Bridge the two worlds
Exporting the API
To export our DLL symbols we define a macro CLR_API:
Notice that we use extern “C” to avoid C++ symbol names mangling.
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