https://gcc.gnu.org/g:1fb5abc3919f376f3dedccad636eba4a4ad7e4a7
commit r16-330-g1fb5abc3919f376f3dedccad636eba4a4ad7e4a7
Author: Patrick Palka <ppa...@redhat.com>
Date: Thu May 1 10:58:50 2025 -0400
c++: more overeager use of deleted function before ADL [PR119034]
The PR68942 fix used the tf_conv flag to disable mark_used when
substituting a FUNCTION_DECL callee of an ADL-enabled call. In this
slightly more elaborate testcase, we end up prematurely calling
mark_used anyway on the FUNCTION_DECL directly from the CALL_EXPR case
of tsubst_expr during partial instantiation, leading to a bogus "use of
deleted function" error.
This patch fixes the general problem in a more robust way by ensuring
the callee of an ADL-enabled call is wrapped in an OVERLOAD, so that
tsubst_expr leaves it alone.
PR c++/119034
PR c++/68942
gcc/cp/ChangeLog:
* pt.cc (tsubst_expr) <case CALL_EXPR>: Revert PR68942 fix.
* semantics.cc (finish_call_expr): Ensure the callee of an
ADL-enabled call is wrapped in an OVERLOAD.
gcc/testsuite/ChangeLog:
* g++.dg/template/koenig13.C: New test.
Reviewed-by: Jason Merrill <ja...@redhat.com>
Diff:
---
gcc/cp/pt.cc | 8 +-------
gcc/cp/semantics.cc | 8 ++++++++
gcc/testsuite/g++.dg/template/koenig13.C | 16 ++++++++++++++++
3 files changed, 25 insertions(+), 7 deletions(-)
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index b45af9360ade..7b296d14a09b 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -21335,13 +21335,7 @@ tsubst_expr (tree t, tree args, tsubst_flags_t
complain, tree in_decl)
/* Avoid error about taking the address of a constructor. */
function = TREE_OPERAND (function, 0);
- tsubst_flags_t subcomplain = complain;
- if (koenig_p && TREE_CODE (function) == FUNCTION_DECL)
- /* When KOENIG_P, we don't want to mark_used the callee before
- augmenting the overload set via ADL, so during this initial
- substitution we disable mark_used by setting tf_conv (68942).
*/
- subcomplain |= tf_conv;
- function = tsubst_expr (function, args, subcomplain, in_decl);
+ function = tsubst_expr (function, args, complain, in_decl);
if (BASELINK_P (function))
qualified_p = true;
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 1aa35d3861ea..43a0eabfa127 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -3325,6 +3325,14 @@ finish_call_expr (tree fn, vec<tree, va_gc> **args, bool
disallow_virtual,
if (type_dependent_expression_p (fn)
|| any_type_dependent_arguments_p (*args))
{
+ if (koenig_p
+ && TREE_CODE (orig_fn) == FUNCTION_DECL
+ && !fndecl_built_in_p (orig_fn))
+ /* For an ADL-enabled call where unqualified lookup found a
+ single non-template function, wrap it in an OVERLOAD so that
+ later substitution doesn't overeagerly mark the function as
+ used. */
+ orig_fn = ovl_make (orig_fn, NULL_TREE);
result = build_min_nt_call_vec (orig_fn, *args);
SET_EXPR_LOCATION (result, cp_expr_loc_or_input_loc (fn));
KOENIG_LOOKUP_P (result) = koenig_p;
diff --git a/gcc/testsuite/g++.dg/template/koenig13.C
b/gcc/testsuite/g++.dg/template/koenig13.C
new file mode 100644
index 000000000000..364bc929579e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/koenig13.C
@@ -0,0 +1,16 @@
+// PR c++/119034
+// { dg-do compile { target c++14 } }
+// A version of koenig12.C involving partial instantiation via a generic
lambda.
+
+void foo(...) = delete;
+
+template <class T> void lookup(T t) { [](auto u) { foo(u); }(t); }
+
+namespace N {
+ struct A { };
+ int foo(A);
+}
+
+int main() {
+ lookup(N::A{});
+}
