Re: pahole and gcc-14 issues

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Mon, Apr 28, 2025 at 04:21:14PM +0100, Alan Maguire wrote:
> In the bad case, the bpf_prog active member:
 
> <2><3d594>: Abbrev Number: 4 (DW_TAG_member)
>     <3d595>   DW_AT_name        : (indirect string, offset: 0x3b976): active
>     <3d599>   DW_AT_decl_file   : 125
>     <3d59a>   DW_AT_decl_line   : 1654
>     <3d59c>   DW_AT_decl_column : 17
>     <3d59d>   DW_AT_type        : <0x4bd05>
 
> ...is a pointer:
> 
>  <1><4bd05>: Abbrev Number: 58 (DW_TAG_pointer_type)
>     <4bd06>   DW_AT_byte_size   : 8
>     <4bd07>   DW_AT_address_class: 2
>     <4bd08>   DW_AT_type        : <0x301cd>
 
> ...which points at an int
 
>  <1><301cd>: Abbrev Number: 214 (DW_TAG_base_type)
>     <301cf>   DW_AT_byte_size   : 4
>     <301d0>   DW_AT_encoding    : 5     (signed)
>     <301d1>   DW_AT_name        : int
>     <301d5>   DW_AT_name        : int
 
> ...but note the the DW_AT_address_class attribute in the latter case and
> the two DW_AT_name values. We don't use that address attribute in pahole
> as far as I can see, but it might be enough to cause problems.

Looks like broken DWARF, there should be just one DW_AT_name per
DW_TAG_base_type, what is the language for the CU where the bad cases
appear? Is some sort of LTO being used?

- Arnaldo