[Bug gdb/28004] DW_AT_ranges with form DW_FORM_sec_offset problem

["vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=28004

--- Comment #7 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Simon Marchi from comment #6)
> > I've tested a patch with both fixes on openSUSE Leap 15.2 x86_64 (gcc 7.5.0,
> > using .debug_ranges), and on openSUSE Tumbleweed x86_64 (gcc 11.1.1, using
> > .debug_rnglists).
> 
> I took a look, and I agree that adding baseaddr here does not make sense, if
> the goal is checking whether the range beginning is 0.
> 

Ack.

> So in all these ranges generated by gcc:
> 
>              DW_AT_name [DW_FORM_line_strp]   
> ("/build/gcc/src/gcc/libstdc++-v3/src/c++98/bitmap_allocator.cc")
>               DW_AT_comp_dir [DW_FORM_line_strp]       
> ("/build/gcc/src/gcc-build/x86_64-pc-linux-gnu/libstdc++-v3/src/c++98")
>               DW_AT_ranges [DW_FORM_sec_offset] (0x00004b50
>                  [0x0000000000000000, 0x0000000000000056)
>                  [0x00000000000a4790, 0x00000000000a479c)
>                  [0x00000000000a47a0, 0x00000000000a47ac)
>                  [0x00000000000a47b0, 0x00000000000a47c8)
>                  [0x0000000000000000, 0x0000000000000026)
>                  [0x00000000000a47d0, 0x00000000000a47e8)
>                  [0x0000000000000000, 0x0000000000000026)
>                  [0x000000000009916c, 0x00000000000991a1)
>                  [0x00000000000991a1, 0x00000000000991d6)
>                  [0x00000000000b1e10, 0x00000000000b1e5b)
>                  [0x0000000000000000, 0x0000000000000011)
>                  [0x0000000000000000, 0x0000000000000011)
> 
>                  ...
> 
> All those starting from 0 are just bad and should not be considered?
> 

I guess so (The comment does mention that it's not uncommon).

> > /me -> vacation for 1 week.
> 
> Hope you have a good time!

I did :)

I've finally found time to work on the test-case and managed to create a dwarf
assembly test-case for this (with .debug_ranges), so I'll probably submit the
fix + test-case this week. [ Perhaps a .debug_rnglists version can be made
easily as well, but I'll look into that after submission. ]

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