Calling C/C++ functions in dynamic and static libraries in D

Question

I'm having trouble wrapping my head around how to interface with C/C++ libraries, both static (.lib/.a) and dynamic (.dll/.so), in D. From what I understand, it's possible to tell the DMD compiler to link with .lib files, and that you can convert .dll files to .lib with the implib tool that Digital Mars provides. In addition, I've come across this page, which implies being able to call functions in .dlls by converting C header files to D interface files. Are both of these methods equivalent? Would these same methods work for Unix library files? Also, how would one reference functions, enums, etc from these libraries, and how would one tell their D compiler to link with these libs (I'm using VisualD, specifically)? If anyone could provide some examples of referencing .lib, .dll, .a, and .so files from D code, I'd be most grateful.

Answer 1

Note you are dealing with three phases for generating an executable. During compilation you are creating object files (.lib/.a are just archives of object files). Once these files are created you use a Linker to put all the pieces together. When dealing with dynamic libraries (.dll, .so) there is the extra step of loading the library when the program starts/during run-time.

During compilation the compiler only needs to be aware of what you are using, it doesn't care if it is implemented. This is where the D interface files come in and are kind of equivalent to Header Files in this respect. Enumerations are declared in the D interface file and must also be defined because they only exist at compile time. Functions and variables can just be declared with no body.

int myFunction(char* str);

The guide for converting a header file to D is in the page you referenced. These files can then be passed to the compiler or exist in the Include Path.

When the linker runs is when you'll need the .lib/.a file. These files can be passed to the compiler which will forward them to the Linker or you can use pragma(lib, "my.lib"); in your program. In both cases the linker must be able to finding at link time (compilation).

In Linux I don't believe there is a difference for linking dynamic and static. In Windows you don't even need the D interface file. Instead you must obtain the function through system calls. I'm really not that familiar with this area, but I suggest Loading Plugins (DLLs) on-the-fly

Update: I can't help much with VisualD, but there is D for .NET Programmers.