On Fri, Feb 14, 2025 at 11:04:09PM +0100, Jason Merrill wrote:
> On 2/14/25 4:29 PM, Marek Polacek wrote:
> > 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 ;-).
>
> Please.
Done:
Tested x86_64-pc-linux-gnu, applying to trunk.
gcc/cp/ChangeLog:
* pt.cc (tsubst_expr) <COMPONENT_REF>: Assign the result of
force_paren_expr.
---
gcc/cp/pt.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 5706a3987c3..62d91a2dd15 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -21713,7 +21713,7 @@ 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 (REF_PARENTHESIZED_P (t))
- force_paren_expr (r);
+ r = force_paren_expr (r);
RETURN (r);
}
else if (type_dependent_expression_p (object))
base-commit: 1dc4e220ca2272d668ddb3041ccd9e69b968e532
--
2.48.1
