[llvm-dev] ORC JIT Weekly #44 -- MachO debugging support enabled

[David Blaikie via llvm-dev]

Awesome!

On Sun, Nov 14, 2021 at 11:26 PM Lang Hames <lhames at gmail.com> wrote:

> Hi All,
>
> OrcRTBridge cleanup has been set aside briefly. Instead of working on that
>> I'm going to take a shot at getting MachO debugging support working in time
>> for the dev meeting.
>
>
> Success! MachO debugging support has landed in [1] (with an obligatory
> round of revert/reapply for bot failures). This support ended up being
> easier to implement than I had hoped, largely thanks to all the
> infrastructure put in place by Stefan Granitz's earlier work on ELF
> debugging, as well as some help from Fred Riss and Jim Ingham. Thanks
> everyone!
>
> The new support has been enabled in the llvm-jitlink tool (we should be
> able to add it to lli soon too). If you want to test it out on Darwin you
> can run:
>
> % clang -O0 -g -c -o my-program.o my-program.c
>
> % lldb llvm-jitlink
> (lldb) settings set plugin.jit-loader.gdb.enable on
> (lldb) b <location in my-program.c>
> (lldb) run my-program.o
>
> If you set a breakpoint on main beware that you'll hit it twice: First
> llvm-jitlink's own main, and then then my-program.o's. Either way, once you
> hit your breakpoint you should then be able to step through JIT'd code.
>
> This is brand new, so please let me know if you run into any issues with
> it. Bug reports are very welcome.
>
> Enabling the support in your own JIT should be relatively straightforward.
> You just need to include llvm/ExecutionEngine/Orc/DebuggerSupportPlugin.h,
> then install the GDBJITDebugInfoRegistrationPlugin in your object linking
> layer. You can see llvm-jitlink's code for this at [2]:
>
>  ObjLayer.addPlugin(ExitOnErr(
>         GDBJITDebugInfoRegistrationPlugin::Create(this->ES, *MainJD, TT)));
>
> In the future we'll try to merge the ELF DebugObjectManagerPlugin and the
> new GDBJITDebugInfoRegistrationPlugin so that you only have to enable the
> one plugin regardless of platform.
>
> -- Lang.
>
> [1]
> https://github.com/llvm/llvm-project/commit/e1933a0488a50eb939210808fc895d374570d891
> [2]
> https://github.com/llvm/llvm-project/blob/0d1d058544446b5fc74e70827a021a017facc56a/llvm/tools/llvm-jitlink/llvm-jitlink.cpp#L1000
>
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