> Could you not do some sort of detection magic, to see if a class name or > class exists prior to manually either calling that functions, or using > NSBundle to load the plugins ?
In practice, "detection magic" is non-trivial :) Figuring out what classes a bundle will create is tricky. You get to load the bundle in memory not as an executable, parse out the mach-o headery bits, figure out which of the images is the one for your process, then parse its objc section to see what it defines. Then (or in parallel) interrogate your current runtime, and make sure there are no collisions with the file you're inspecting and what you've already got loaded. And if there are no collisions, you can try to load the image... ...And then you hope that they aren't doing dynamic class creation, because you'll have a hard time figuring that out. And then you resort to inspecting their symbol table to see if they're making any objc runtime calls, and you hope that they aren't using dyld functions to resolve them, and if they are you then have to check for dyld's entry points too, and you also have to hope that they aren't divining them by fishing them out by manually traversing their in-memory image (which will have some linkage bits for free). ...And then if you're feeling really industrious, you can shim the objc runtime calls to create classes, thinking you'll nail them at load time and do something sensible. Except that they can have a load-time C function detect and/or modify your shim. So then you go and muck with madvise and friends to see who's messing with your bits, only to find that ultimately everything you can do they can undo, and you remember how great protected memory is, and how much nicer it would be if we had even more of it :) I've done stuff that will require one to complete the first paragraph, and a sentence or two from the second, and pieces of the third. It's a tricky problem, and there isn't really a good solution to it. If you're writing an App, and you know for certain that you don't need the user's installed plugins, it's possible a [QCPlugin dontLoadUserPlugins] method would fix you up, but if you're writing middle ware that'll just get in the way of someone else who does need them... -- Christopher Wright christopher_wri...@apple.com
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