Re: [PATCH] gdb: tighten assertions in set_type_vptr_*

[Kevin Buettner <kevinb@redhat.com>]

On Mon, 26 Jan 2026 10:54:00 -0500
Simon Marchi <simon.marchi@efficios.com> wrote:

> From: Simon Marchi <simon.marchi@efficios.com>
> To: gdb-patches@sourceware.org
> Cc: Simon Marchi <simon.marchi@polymtl.ca>
> Subject: [PATCH] gdb: tighten assertions in set_type_vptr_*
> Date: Mon, 26 Jan 2026 10:54:00 -0500
> 
> From: Simon Marchi <simon.marchi@polymtl.ca>
> 
> In C++, only structures and classes (represented by TYPE_CODE_STRUCT)
> can participate in inheritance.  I therefore think it does not make
> sense to allow for TYPE_CODE_UNION in set_type_vptr_basetype and
> set_type_vptr_fieldno.  Remove the possibility for the type to be a
> union in these functions.
> 
> Also, for the same reason, add an assertion that checks the type of
> basetype in set_type_vptr_basetype.
> 
> I did not change the getters (internal_type_vptr_fieldno and
> internal_type_vptr_basetype), because it seems like they are called by
> code that handles similarly both structures and unions.  Making those
> stricter would require adding conditions in those callers, which doesn't
> look like an improvement.  For unions, they will correctly return an
> "invalid" value.
> 
> Change allocate_cplus_struct_type to not use set_type_vptr_fieldno to
> initialize the field to -1, otherwise it would trip the assertion when
> initializing for a union type.

Makes sense to me...

Approved-by: Kevin Buettner <kevinb@redhat.com>