> On Apr 29, 2015, at 10:04 AM, Eric Christopher <[email protected]> wrote:
>
>
>
> On Wed, Apr 29, 2015 at 9:58 AM Eric Christopher <[email protected]
> <mailto:[email protected]>> wrote:
> On Wed, Apr 29, 2015 at 8:20 AM Adrian Prantl <[email protected]
> <mailto:[email protected]>> wrote:
>
> > On Apr 28, 2015, at 6:26 PM, David Blaikie <[email protected]
> > <mailto:[email protected]>> wrote:
>
> > Could you revert & I'll look into getting you a reduced test
> > case/demonstration of the issue? (can you run GDB 7.5? Perhaps a simple
> > test case would demonstrate the issue if you're lucky, otherwise I can
> > reduce one from the failing test case)
>
> I reverted the commit in r236110. I probably won’t need a reduction — my
> guess from the log is that gdb expects a local variable to be present.
>
> My suggestion is to emit local artificial shadow variables and then weaken
> the Verifier to not verify artificial variables. In a next step, we could use
> the new debugger tuning target feature to make the artificial local variables
> and the weakened verifier a gdb-specific behavior, file a bug against gdb,
> and eventually remove it altogether.
>
>
> FWIW I don't want to use the "tuning" parameters to also affect correctness.
>
> OK. Dave and I debated this a little in person, here's a proposal:
>
> by default it will have the gdb specific behavior, but if you're tuning for
> lldb (or any other debugger I guess?) it won't be there.
>
> Thoughts?
I think it’s a fair assumption that many debuggers won’t deal very well with
anonymous local variables, from that perspective this is the right decision.
(Nitpick: If it is only needed for GDB then it doesn’t seem right to make it
the global default, because tuning for gdb will be the default on all
non-lldb/sce platforms anyway.)
I really want to push towards making the debug info handling stricter, so I’m
unhappy about having the frontend willfully emit broken IR at the moment. But,
I also haven’t found a way to emit the local shadow variables in a way that
makes the verifier happy and isn’t entirely gross in other respects. I’ll keep
looking for a better way to emit this without having to relax the verifier.
-- adrian
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