Runtime.loadLibrary/unloadLibrary need .getSymbol()

[dlangBugzillaToGithub]

Alvaro reported this on 2011-03-27T14:46:07Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=5789

CC List

• Walter Bright (@WalterBright)
• Martin Nowak (@MartinNowak)
• Vruyr Gyolchanyan

Description

Runtime.loadLibrary()/unloadLibrary() are very handy to load DLLs in a platform independent way, without using directly the platform's LoadLibrary()/UnloadLibrary() or dlopen()/dlclose().

But these two are missing a third very important function: a function to load the address of a given symbol in the shared library. E.g. the equivalent GetProcAddress() in Windows or dlsym() in Linux.

To keep the current simplicity in Phobos, where the library is just referenced by a void*, the new functions could be:

  void* Runtime.getLibrarySymbol(void* libhandle, string symbol);

Libraries such as gtkD are currently doing a lot of dynamic loading and use platform specific functions with version(Windows){...}else{...} conditions. That could be avoided and simplified with the above.

--

Anyway I'd favor a little DynLibrary class allowing:

  auto lib = new DynLibrary("mylib");  // ".dll" or ".so" autoappended
  Function f = lib["main_function"];

BTW, autoappending the extension in Runtime.loadLibrary() would be great to ease program portability. Not sure if it's already like that.

--


Also (this could be a different request report) it would be great to have an additional function in dynamic libraries: a "factory" function to create objects from classes defined inside the DLL (great for plugins for example).

There is already Object.factory("module.Class"); which works great but only locally. Can't that be supported for loaded libraries?

either with a new call:

  Runtime.libraryFactory(void* libhandle, string classname);

or

  lib.factory("class");

or just making the library, in its init code, add its classes to the calling runtime so that Object.factory("mydll.Classname") does it.

[dlangBugzillaToGithub]

code (@MartinNowak) commented on 2014-06-15T19:40:38Z

There is a pull request for this issue this which needs some more work to get accepted.
https://github.com/D-Programming-Language/druntime/pull/617