[PATCH] D67097: [DWARF] Check for format mismatch between CU and Range List Table.

Wed Sep 4 14:21:30 PDT 2019

dblaikie added a comment.

In D67097#1657964 <https://reviews.llvm.org/D67097#1657964>, @probinson wrote:

> In D67097#1656268 <https://reviews.llvm.org/D67097#1656268>, @dblaikie wrote:
>
> > I'm not sure if using "OffsetIn" in the diagnostic is the right thing to do.
> >
> > Honestly the fact that DWARFv5 specifies that the "rnglist base address" (& loclist bast address, and str_offsets base) point to the beginning of the list rather than the start of the header is super quirky and I don't think it's helpful to users to highlight that. (though I doubt DWARFvNext would bother fixing this - it'sjust quirky, not super problematic for any practical reasons I can think of)
>
>
> IIRC this is one of Cary's, and argued that it could be directly used to index into section, instead of you having to step past the header to use it.  Anyway we let him get away with it, for better or worse.

Meh, I can't imagine the (Start+Header)[N] would be too expensive (& Start+Header could be computed once/ahead of time easily enough).

> It would have to be essentially unusable or horribly inefficient, for the committee to be willing to change it now.

Not sure what would be unusable or inefficient about it - could you explain more?

I'd figure if DWARFvNext changed the semantics of the various *_base attributes, then an implementation would look at the CU version to decide whether it should walk backwards to find the header, or forwards to find the list.

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https://reviews.llvm.org/D67097