Re: [PATCH][gdb/symtab] Force usage of all_comp_units.size (CU/TU/CUTU)

[Tom de Vries via Gdb-patches <gdb-patches@sourceware.org>]

On 7/14/22 16:43, Tom de Vries wrote:
> It's hard to produce a test-case for this, but let's try at least to trigger
> the complaint somehow.  We start out by creating an exec with .debug_types and
> .debug_names:
> ...
> $ gcc -g ~/hello.c -fdebug-types-section
> $ gdb-add-index -dwarf-5 a.out
> ...
> and verify that we don't see any complaints:
> ...
> $ gdb -q -batch -iex "set complaints 100" ./a.out
> ...
> 
> We look at the CU and TU table using readelf -w and conclude that we have
> nr_cus == 6 and nr_tus == 1.
> 
> Now override ull in dw2_debug_names_iterator::next for the DW_IDX_compile_unit
> case to 6, and we have:
> ...
> $ gdb -q -batch -iex "set complaints 100" ./a.out
> During symbol reading: .debug_names entry has bad CU index 6 [in module a.out]
> ...
> 
> [ After this, it still crashes because this code in
> dw2_debug_names_iterator::next:
> ...
>    /* Skip if already read in.  */
>    if (m_per_objfile->symtab_set_p (per_cu))
>      goto again;
> ...
> is called with per_cu == nullptr, but I consider this a separate issue. ]
> 
> Now revert the fix (all_comp_units.size (CU) -> all_comp_units.size (CUTU))
> and observe that the complaint disappears, so we've confirmed that the fix is
> required.

I've submitted a test-case for this here ( 
https://sourceware.org/pipermail/gdb-patches/2022-August/191274.html ).

Thanks,
- Tom