Re: Question about struct type* ownership

["Jan Vraný via Gdb" <gdb@sourceware.org>]

On Wed, 2025-01-08 at 17:30 -0700, Tom Tromey wrote:
> Jan> Let's say I'd like to create new function type "int(struct s)",
> where
> Jan> type "int" is arch-owned and "struct s" is objfile-owned. Am I
> correct
> Jan> thinking that resulting function type should be objfile-owned? 
> 
> Yes, in particular by the same objfile that owns "struct s".
> 
> Jan> Generally speaking, if composing new type out of other types, if
> at
> Jan> least one of the types is objfile-owned then the new type must
> by
> Jan> also objfile-owned (by that very objfile), right? 
> 
> Yes.
> 
> Jan> Looking at lookup_function_type_with_arguments, it allocated new
> Jan> function type is always "owned" by whoever "owns" the return
> type
> Jan> (first param to lookup_function_type_with_arguments). So if I'm
> correct
> Jan> about the above, I'd have to extend
> lookup_function_type_with_arguments
> Jan> to pass down type allocator (like in create_array_type). Or is
> there
> Jan> a better way?
> 
> It's new territory, so just whatever looks reasonably clean.  I think
> in
> the past this wasn't an issue because essentially only symbol readers
> made types.

OK, I'll refactor the code a bit then. Thanks!

> 
> Jan> Also, when experimenting with the example above, I realized
> that 
> Jan> the arch-owner of "int" struct type* is a different struct
> gdbarch *
> Jan> then gdbarch associated with objfile-owner of "struct s" type
> Jan> (i mean, pointer values are different).
> Jan> While I would think it is okay to compose new type from types
> owned by 
> Jan> two distinct gdbarchs from lifecycle POV, it still puzzles me
> why
> Jan> there are two different gdbarch instances (both are i386:x86-
> 64)?
> 
> Offhand I don't know but there are a lot of ways a gdbarch can be
> initialized.  Maybe they have different registers available.

OK, so I'll assume this is normal. Thanks! 

Jan