Re: [RFA 3/5] Use std::string, std::vector in rust-lang.c

[Tom Tromey <tom@tromey.com>]

>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:

Pedro> There's a GNU extension that I think is meant to make it possible
Pedro> for the debugger to treat uninitialized variables
Pedro> specially (DW_OP_GNU_uninit), though I don't think we do
Pedro> much with it.

There were never any docs for it :(
I think it probably should have been a piece-terminating operation but
it was never clear if this was how it was actually supposed to work.
I stuck a comment in dwarf_expr_require_composition to this effect back
in the day.

Pedro> Not sure gcc emits it, even.

It does, but I don't know under what conditions.
There's code in dwarf2out.c like:

  if (initialized == VAR_INIT_STATUS_UNINITIALIZED)
    add_loc_descr (&result, new_loc_descr (DW_OP_GNU_uninit, 0, 0));

I don't know when that happens though.

Perhaps this could be cleaned up a bit, say by making DW_OP_GNU_uninit a
piece terminator (I forget the official term here) and by changing gcc
to emit a location list that indicates that the object is uninitialized
until after the constructor is run.  It might be a little friendlier to
users, dunno.

Tom