On Thu, Aug 25, 2022 at 09:25:43AM -0400, Jason Merrill wrote:
> On 8/24/22 17:30, Marek Polacek wrote:
> > On Tue, Aug 23, 2022 at 05:27:00PM -0400, Jason Merrill wrote:
> > > On 8/23/22 09:39, Marek Polacek wrote:
> > > > + tree arg = CALL_EXPR_ARG (fn, 0);
> > > > + extract_op (arg);
> > > > + if (TREE_CODE (arg) == ADDR_EXPR)
> > > > + arg = TREE_OPERAND (arg, 0);
> > > > + tree type = TREE_TYPE (lhs);
> > > > + lhs = maybe_undo_parenthesized_ref (lhs);
> > > > + STRIP_ANY_LOCATION_WRAPPER (lhs);
> > > > + const bool print_var_p = (DECL_P (lhs)
> > > > + || REFERENCE_REF_P (lhs)
> > > > + || TREE_CODE (lhs) == COMPONENT_REF);
> > >
> > > Why include REFERENCE_REF_P and COMPONENT_REF? Reference refs should be
> > > stripped before this test, member refs aren't variables.
> >
> > I'm checking REFERENCE_REF_P and COMPONENT_REF to say "moving a variable"
> > in #1 and #3. The REFERENCE_REF_P check means that we also say "variable"
> > for #2. Sure, "A variable is introduced by the declaration of a reference
> > other than a non-static data member", but I'm not sure if users care about
> > that here?
> >
> > If I strip REFERENCE_REFs before the check then the result will be the
> > same.
>
> That's what I was suggesting, yes: Strip the REFERENCE_REF so DECL_P can see
> the decl.
Ok, I've added the REFERENCE_REF stripping. But I've still left the
COMPONENT_REF in. Perhaps we could say "moving a member" to itself for
COMPONENT_REFs. Or just say "moving 'x' of type 'int' to itself" and
avoid all of this. :)
> I don't see where COMPONENT_REF comes in?
For #1 in the test below the COMPONENT_REF was created in finish_id_expression
-> finish_non_static_data_member -> build_class_member_access_expr and passed
down to maybe_warn_self_move from here:
#0 maybe_warn_self_move (loc=2147483652, lhs=<component_ref 0x7fffea380e10>,
rhs=<indirect_ref 0x7fffea38a220>) at
/home/mpolacek/src/gcc/gcc/cp/typeck.cc:8908
#1 0x0000000000f3d03e in cp_build_modify_expr (loc=2147483652,
lhs=<component_ref 0x7fffea380e10>,
modifycode=NOP_EXPR, rhs=<indirect_ref 0x7fffea38a220>, complain=3)
at /home/mpolacek/src/gcc/gcc/cp/typeck.cc:9161
#2 0x0000000000f3e461 in build_x_modify_expr (loc=2147483652,
lhs=<component_ref 0x7fffea380e10>,
modifycode=NOP_EXPR, rhs=<indirect_ref 0x7fffea38a220>, lookups=<tree 0x0>,
complain=3)
at /home/mpolacek/src/gcc/gcc/cp/typeck.cc:9446
#3 0x0000000000d92d4e in cp_parser_assignment_expression
(parser=0x7fffea236850, pidk=0x0, cast_p=false,
decltype_p=false) at /home/mpolacek/src/gcc/gcc/cp/parser.cc:10461
> > Or I could keep only the DECL_P check, but then we'll say "moving
> > an expression" for #1 and #2, which seems strange.
> >
> > struct S {
> > int x;
> > int &r;
> > void foo () {
> > x = std::move (x); // #1
> > r = std::move (r); // #2
> > };
> > };
> >
> > void
> > foo (int &r)
> > {
> > r = std::move (r); // #3
> > }
Marek
