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

[Lang Hames via llvm-dev]

> So no JIT for i386?

I didn't realise i386 still used ObjC 1 - all my experiments were on arm64.

i386 support for ObjC would be nice to have, but it's not a blocker for
adding ObjC 2 support.

- Lang.


On Thu, Oct 20, 2016 at 11:57 AM, Steven Wu <stevenwu at apple.com> wrote:

>
>
>
> On Oct 19, 2016, at 11:28 AM, Stanislav Pankevich <s.pankevich at gmail.com>
> wrote:
>
> Hi Lang, Steven,
>
> At this point it seems that the best next step is for Steven to share his
> code, right? Or is there some other work that can be done in parallel?
>
>
> It will take some time to create patch from my existing implementation.
> After that, we still need to correctly register the implementation to objc
> runtime. I dont expect this to be a quick task.
>
>
> Lang? Steven?
>
> Here’s small note about my interest here: Alex Denisov and I are working
> on a tool for mutation testing https://github.com/AlexDenisov/mutang.
> Alex has made fascinating progress towards mutation testing of C++ code and
> we would also like to bring mutation testing to iOS where we are by
> profession. Currently inability to run Objective-C code via JIT is a
> critical dependency for our progress on iOS part so I'll be happy to help
> with this in any way even though my experience with LLVM is very limited.
>
>
> This sounds like an interesting project. Maybe you can generate the object
> file and statically linked the mutated code for now?
>
> Steven
>
>
> Thanks.
>
> Stanislav
>
> On 19 Oct 2016, at 01:49, Lang Hames <lhames at gmail.com> wrote:
>
> 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.
>
>
> So no JIT for i386?
>
> Steven
>
>
> 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
>>>
>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>>
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>>
>
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