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Yes. 1st restriction above is more for business reasons, so that there are no ways to circumvent the app store, while 2nd is a technical restriction on 3rd part
by codedivine 14y ago
Yes. 1st restriction above is more for business reasons, so that there are no ways to circumvent the app store, while 2nd is a technical restriction on 3rd party apps for security purposes. Apple apps (like Safari) can obviously do JIT compilation.
However, I speculate even the 2nd restriction is partly for business reasons because it prevents some third-party toolkits (such as those compiling to LLVM) from achieving high performance. You might remember that Adobe was compiling Flash to LLVM to allow devs to port their Flash apps to iOS, but since LLVM cannot do proper JIT compilation on iOS, it will reduce performance.
FWIW: WinRT imposes both the restrictions above. Android technically doesn't impose either for sideloaded apps. But if you want to distribute app through Google Play, the 1st restriction is indeed imposed.
- mistercow 14y ago>Apple apps (like Safari) can obviously do JIT compilation. I hadn't considered this before, but that means that you could potentially use JS as an intermediate representation for other languages in order to leverage Safari's JIT under iOS. Probably too inefficient to be worthwhile for any language that isn't a dialect of JS, but an intriguing concept nonetheless.
- nickmain 14y agoThe ability to execute from writable memory is enforced at the process level, and only Safari and a few other Apple apps get that permission. Javascript in Safari is jitted - but JS in a UIWebView used by a third-party app is not.
- jmccaffrey 14y agoGotta love android, you can cheerfully mprotect away the write-protection on executable pages. I've done some dynamic stub code removal that way. Worst case, you can only hose your own process.
- mistercow 14y agoWell that's a relief. Now I don't have to feel bad about not turning that idea into a proof of concept.