Question about struct type* ownership

[Tom Tromey]

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.

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.

Tom