D equivalent of run-time DLLs / Plugins

[Ali Çehreli via Digitalmars-d-learn]

On 02/29/2016 02:40 PM, Chris Katko wrote:

> I want
> to link to piece of D code at run-time. I want my D program to load,
> scan for files which are whatever D-equivalent of a DLL/SO is, and load
> those as well. Calling library functions, and having them call my core
> functions.

It's the same as in C. Assuming that you have a ./libxyz.so that 
contains library_function() of type 'int library_func(int)', the 
following works:

import std.stdio;
import core.sys.linux.dlfcn;

extern(C) int library_func(int);
alias FuncType = int function(int);

int main()
{
     void * lib = dlopen("./libxyz.so", RTLD_NOW);

     if (!lib) {
         stderr.writefln("Failed to open library");
         return 1;
     }

     auto func = cast(FuncType)dlsym(lib, "library_func");

     if (!func) {
         stderr.writefln("Failed to find function");
         return 1;
     }

     writefln("Result: %s", func(10));

     return 0;
}

Ali