[Lldb-commits] [lldb] Improve performance of .debug_names lookups when DW_IDX_parent attributes are used (PR #91808)

[Felipe de Azevedo Piovezan via lldb-commits]

felipepiovezan wrote:

> @felipepiovezan I have another question. For the same example. I see:
> 
> ```
> Name 4 {
>       Hash: 0x2F94396D
>       String: 0x00000049 "_Z9get_statev"
>       Entry @ 0x112 {
>         Abbrev: 0x2
>         Tag: DW_TAG_subprogram
>         DW_IDX_die_offset: 0x00000023
>         DW_IDX_parent: <parent not indexed>
>       }
> ...      
> Name 8 {
>       Hash: 0x2B607
>       String: 0x00000041 "B"
>       Entry @ 0x13b {
>         Abbrev: 0x7
>         Tag: DW_TAG_namespace
>         DW_IDX_type_unit: 0x00
>         DW_IDX_die_offset: 0x00000025
>         DW_IDX_parent: Entry @ 0x112
>       }
> ```
> 
> This seems like a bug no? Looks like it's confusing
> 
> ```
> 0x00000023:   DW_TAG_namespace
>                 DW_AT_name  ("A")
> ```
> 
> In TU 0 With Subprogram at the same (relative offset) in the CU
> 
> ```
> 0x0000006a: Compile Unit: length = 0x0000005c, format = DWARF32, version = 0x0005, unit_type = DW_UT_compile, abbr_offset = 0x0000, addr_size = 0x08 (next unit at 0x000000ca)
> ...
> 0x0000008d:   DW_TAG_subprogram
> ```
> 
> I think it should be pointing to:
> 
> ```
> String: 0x00000023 "A"
>       Entry @ 0x11e {
>         Abbrev: 0x4
>         Tag: DW_TAG_namespace
>         DW_IDX_type_unit: 0x00
>         DW_IDX_die_offset: 0x00000023
>         DW_IDX_parent: <parent not indexed>
>       }
> ```

You are right. The fact that they have the same relative offset tells me that some part of the code is failing to account for TUs. I just checked the printing code in the hope that it was a mistake while dumping, but it doesn't seem to be...

https://github.com/llvm/llvm-project/pull/91808