[PATCH] D65035: [DebugInfo] Don't emit incorrect descriptions of thunk params (PR42627)

[Adrian Prantl via Phabricator via llvm-commits]

aprantl added a comment.

In D65035#1615910 <https://reviews.llvm.org/D65035#1615910>, @dblaikie wrote:

> In D65035#1615906 <https://reviews.llvm.org/D65035#1615906>, @vsk wrote:
>
> > In D65035#1615888 <https://reviews.llvm.org/D65035#1615888>, @dblaikie wrote:
> >
> > > In D65035#1615833 <https://reviews.llvm.org/D65035#1615833>, @aprantl wrote:
> > >
> > > > In D65035#1615819 <https://reviews.llvm.org/D65035#1615819>, @dblaikie wrote:
> > > >
> > > > > In D65035#1615787 <https://reviews.llvm.org/D65035#1615787>, @aprantl wrote:
> > > > >
> > > > > > It's likely better for the tools to know where each function starts *and ends*.
> > > > >
> > > > >
> > > > > __attribute__((nodebug)) breaks that invariant (& I think there's other functions we emit without debug info too - maybe some things to do with global ctors?)
> > > >
> > > >
> > > > Correct, and the tools need to fall back to heuristics in these cases. I don't know whether this causes any problems in practice.
> > > >
> > > > >> More importantly though, if we don't generate debug info for the thunk, can we describe the function itself after it became inlined into the thunk?
> > > > > 
> > > > > Not really, no - and GCC doesn't describe the inlining either. A backtrace would demangle the name of the thunk & that's about all it could show there.
> > > >
> > > > *That* sounds like a good reason to keep the debug info for the thunks around.
> > >
> > >
> > > Not sure I follow why demangling the symbol would result in a worse user experience than the debug info? About the only thing in the debug info is the mangled name that's in the symbol table too.
> >
> >
> > Oh, wouldn't the debugger lose the ability to synthesize an [inlined] frame for whatever is inlined into the thunk?
>
>
> True, true - you'd lose any variable descriptions etc. Fair point.


That's what I meant. Sorry for not expressing that better!


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