[Lldb-commits] [PATCH] D68655: Trust the arange accelerator tables in dSYMs

[Pavel Labath via Phabricator via lldb-commits]

labath added a comment.

In D68655#4048009 <https://reviews.llvm.org/D68655#4048009>, @jasonmolenda wrote:

> In D68655#4047126 <https://reviews.llvm.org/D68655#4047126>, @labath wrote:
>
>> In D68655#4045895 <https://reviews.llvm.org/D68655#4045895>, @jasonmolenda wrote:
>>
>>> Both have to be written by the dwarf linker to be correct, but only the former is written ONLY by the dwarf linker.
>>
>> I don't think that's right:
>>
>>   $ clang -c -x c - -o - -gdwarf-aranges -g <<<"void f(){}" | llvm-readelf - --sections | grep aranges
>>     [ 6] .debug_aranges    PROGBITS        0000000000000000 0000a0 000030 00      0   0  1
>>     [ 7] .rela.debug_aranges RELA          0000000000000000 000380 000030 18   I 20   6  8
>
> Ah thanks Pavel, clang on Darwin doesn't emit this in .o files.

It does. It just doesn't do it by default -- same as on linux (but not on PS4 I believe). You have to use the -gdwarf-aranges flag explicitly (which, quite possibly, noone does),

> So in this case, the .o file has a DW_TAG_compile_unit with a DW_AT_ranges and a .debug_aranges, both generated pre-link-time by the compiler.

Yes.

> And Greg is saying that the DW_AT_ranges list in the final executable will be better than the .debug_aranges?  I don't know how strongly he asserts this - today if a .debug_aranges has an entry, we don't look at DW_TAG_compile_unit's DW_AT_ranges, or create the ranges ourself via the line table; the debug_aranges is trusted above the other methods if it includes CU.

That I don't know. Personally, I would expect the two to be equivalent, except that the debug_aranges could theoretically be faster to parse (and takes up more space).


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