On Fri, Feb 14, 2025 at 09:30:34AM -0500, Patrick Palka wrote:
> On Thu, 13 Feb 2025, Marek Polacek wrote:
>
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> >
> > -- >8 --
> > Here we have:
> >
> > template<typename T>
> > struct X{
> > T val;
> > decltype(auto) value(){
> > return (val);
> > }
> > };
> >
> > where the return type of value should be 'int &' since '(val)' is an
> > expression, not a name, and decltype(auto) performs the type deduction
> > using the decltype rules.
> >
> > The problem is that we weren't propagating REF_PARENTHESIZED_P
> > correctly: the return value of finish_non_static_data_member in this
> > test was a REFERENCE_REF_P, so we didn't set the flag. We should
> > use force_paren_expr like below.
> >
> > PR c++/116379
> >
> > gcc/cp/ChangeLog:
> >
> > * pt.cc (tsubst_expr) <COMPONENT_REF>: Use force_paren_expr to set
> > REF_PARENTHESIZED_P.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/cpp1y/decltype-auto9.C: New test.
> > ---
> > gcc/cp/pt.cc | 4 ++--
> > gcc/testsuite/g++.dg/cpp1y/decltype-auto9.C | 15 +++++++++++++++
> > 2 files changed, 17 insertions(+), 2 deletions(-)
> > create mode 100644 gcc/testsuite/g++.dg/cpp1y/decltype-auto9.C
> >
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index a2fc8813e9d..5706a3987c3 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -21712,8 +21712,8 @@ tsubst_expr (tree t, tree args, tsubst_flags_t
> > complain, tree in_decl)
> > {
> > r = finish_non_static_data_member (member, object, NULL_TREE,
> > complain);
> > - if (TREE_CODE (r) == COMPONENT_REF)
> > - REF_PARENTHESIZED_P (r) = REF_PARENTHESIZED_P (t);
> > + if (REF_PARENTHESIZED_P (t))
> > + force_paren_expr (r);
>
> Looks like this is the first use of force_paren_expr whose result we
> ignore. If r is a decl then force_paren_expr returns a new tree
> wrapping it, which we'd lose by ignoring the result -- or is that not
> possible at this call site?
I don't see how finish_non_static_data_member would return a DECL.
But I can add "r = " if preferred ;-).
Marek
