[llvm-dev] A question to the DWARF experts on symbol indirection

[via llvm-dev]

> -----Original Message-----
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Tim
> Northover via llvm-dev
> Sent: Wednesday, July 25, 2018 3:07 AM
> To: Nat!
> Cc: LLVM Developers Mailing List
> Subject: Re: [llvm-dev] A question to the DWARF experts on symbol
> indirection
> 
> Hi Nat!,
> 
> On Wed, 25 Jul 2018 at 01:21, Nat! via llvm-dev <llvm-dev at lists.llvm.org>
> wrote:
> > Is it possible to emit DWARF statements, so that in the debugger the
> > parameter _param is hidden and the visibility is a and b, without a
> _param-> prefix ?
> 
> It's certainly possible in LLVM IR. @llvm.dbg.declare and so on can
> associate arbitrary Values in a function with whatever name you want.

DWARF expressions are certainly powerful enough to describe this.

> 
> But it looks like you're trying to convince Clang itself to do that.
> That's likely to be harder since it's not exactly a natural C mapping;
> I suspect a lot depends on just where you're doing your ABI lowering.

Also depends on whether you want your debugger to be able to call these
functions.

My guess is that you want to describe the formal parameter as artificial,
using the proper struct description, so that calls work correctly.
Then create local variables whose storage locations work indirectly off
the (described as artificial) pointer parameter.

Whether you get your modified front-end to do this, or hack up the
backend, up to you.  The question was *can* it be done, and the answer
to that is clearly yes.
--paulr

> Either way you're probably more likely to get a good response if you
> ask the question on the cfe-dev mailing list.
> 
> Cheers.
> 
> Tim.
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