Re: [PATCH] gdb: fix gdbarch_tdep ODR violation

[John Baldwin <jhb@FreeBSD.org>]

On 11/12/21 12:42 PM, Simon Marchi via Gdb-patches wrote:
> I would like to be able to use non-trivial types in gdbarch_tdep types.
> This is not possible at the moment (in theory), because of the one
> definition rule.
> 
> To allow it, rename all gdbarch_tdep types to <arch>_gdbarch_tdep, and
> make them inherit from a gdbarch_tdep base class.  The inheritance is
> necessary to be able to pass pointers to all these <arch>_gdbarch_tdep
> objects to gdbarch_alloc, which takes a pointer to gdbarch_tdep.
> 
> These objects are never deleted through a base class pointer, so I
> didn't include a virtual destructor.  In the future, if gdbarch objects
> deletable, I could imagine that the gdbarch_tdep objects could become
> owned by the gdbarch objects, and then it would become useful to have a
> virtual destructor (so that the gdbarch object can delete the owned
> gdbarch_tdep object).  But that's not necessary right now.
> 
> It turns out that RISC-V already has a gdbarch_tdep that is
> non-default-constructible, so that provides a good motivation for this
> change.
> 
> Most changes are fairly straightforward, mostly needing to add some
> casts all over the place.  There is however the xtensa architecture,
> doing its own little weird thing to define its gdbarch_tdep.  I did my
> best to adapt it, but I can't test those changes.

I haven't reviewed in detail, but I'm a big fan of this change.  If nothign
else it makes it easier to debug gdb itself since 'p (gdbarch_tdep *)foo'
will no longer be ambiguous.

-- 
John Baldwin