[llvm-dev] Is it possible to execute Objective-C code via LLVM JIT?

[Lang Hames via llvm-dev]

Hi Steven,

That sounds great. The object file parser would definitely be of interest
to JIT clients. Having ObjC 1 support would be nice, but I don't see it as
a blocker to committing what you've got: all code produced by the JIT is
going to be ObjC-2.

Cheers,
Lang.

On Tue, Oct 18, 2016 at 2:22 PM, Steven Wu <stevenwu at apple.com> wrote:

> Hi Stanislav, Lang
>
> I have a version of objc metadata parser based on LLVM which can handle
> objc2 metadata from MachO object and bitcode (bitcode version is even swift
> compatible). I don't know if there is enough interest for me to upstream
> it. It probably requires some work to clean up the interface and complete
> it by adding objc1 support and other object format support.
>
> Steven
>
> On Oct 18, 2016, at 2:10 PM, Lang Hames via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> Hi Stanislav,
>
> I actually looked into this recently. It is possible, but takes some
> non-trivial effort right now: You have to hook into the JIT memory
> allocator, parse the objective C metadata sections in the object file, then
> call the objective C runtime to register any newly added classes, protocols
> and selectors.
>
> I can't release my code as-is: I built it against a hacked up copy of the
> runtime. The right way to do this would be to write parsers for the
> objective C metadata, and an Objective-C registration call that uses the
> parsers and calls the runtime. These should be made available conditionally
> if the objective C runtime headers are available. This is something that
> I'd like to get to eventually, but I have a long to-do list. If you or
> anyone you know is interested in working on it I'd be happy to provide
> pointers and code review.
>
> Cheers,
> Lang.
>
> On Tue, Oct 18, 2016 at 1:33 PM, Stanislav Pankevich via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hello,
>>
>> Is it possible to execute Objective-C code using LLVM JIT?
>>
>> The original point for my research is this topic on StackOverflow:
>>
>> All selectors unrecognised when invoking Objective-C methods using the
>> LLVM ExecutionEngine http://stackoverflow.com/questions/10375324/
>> all-selectors-unrecognised-when-invoking-objective-c-
>> methods-using-the-llvm-exec
>>
>> Running that example with lli produces the following output:
>>
>> 2016-10-18 21:25:58.332 lli[12970:169282] *** NSForwarding: warning:
>> selector (0x10356a38f) for message 'alloc' does not match selector known to
>> Objective C runtime (0x7fff8e93afb5)-- abort
>> 2016-10-18 21:25:58.334 lli[12970:169282] +[NSAutoreleasePool alloc]:
>> unrecognized selector sent to class 0x7fff7a562130
>> 2016-10-18 21:25:58.338 lli[12970:169282] *** Terminating app due to
>> uncaught exception 'NSInvalidArgumentException', reason:
>> '+[NSAutoreleasePool alloc]: unrecognized selector sent to class
>> 0x7fff7a562130'
>>
>> See also additional discussion here: https://twitter.com/sbpa
>> nkevich/status/783363161537798144.
>>
>> Thanks.
>>
>> Stanislav Pankevich
>>
>>
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>>
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