[llvm-dev] Collecting address ranges in DWARFUnit::collectAddressRanges. (original) (raw)

Rafael Avila de Espindola via llvm-dev llvm-dev at lists.llvm.org
Thu Nov 16 15:47:00 PST 2017

David Blaikie via llvm-dev <llvm-dev at lists.llvm.org> writes:

On Thu, Nov 16, 2017 at 11:44 AM Robinson, Paul <paul.robinson at sony.com> wrote:

There's no requirement that DWATranges (or high/lowpc) appear on the skeleton CU rather than the DWO CU. So it's quite possible that to get the address ranges covered by the CU one would need to look in the DWO, I think?

Is that not correct/have I misunderstood something there? The DWO isn't supposed to contain addresses (because it isn't supposed to contain relocations). In DWARF 5 the DWO can have FORMaddrx references to the .debugaddr section in the main .o file, which allows the DWO to contain DIEs/attributes that should have address values, because the actual address values are still in the .o file; but before that anything that's an address really can't go into the DWO. DWOs didn't exist (in a standard form) before DWARF 5, right? Insofar as they did exist (in a non-standard form) they have always supported FORMaddrindex to reference addresses in .debugaddr in the main .o. But the lowpc/highpc/ranges attributes would appear in the .dwo, using a FORMaddrindex/FORMaddrx - so if you want to collect the address range of a CU you might need to load the .dwo to do so. That's the crux of what I was getting at: To get the address range a CU covers, you may need to read the .dwo.

Is it possible to add a test for that? I can confirm that the attached patch causes not failures on llvm, clang or lld tests.

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