From: Jason Merrill <jason@redhat.com>
Date: Fri, 9 May 2025 15:05:13 +0000 (-0400)
Subject: c++: CWG2369 workaround and ... [PR120185]
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=21842fe301caa5dbc69a69033cdc17bb29b8c399;p=thirdparty%2Fgcc.git

c++: CWG2369 workaround and ... [PR120185]

My r16-479 adjustment to the PR99599 workaround broke on a class with a
varargs constructor.

It also occurred to me that we don't need to do non-dep conversion checking
in two phases when concepts aren't supported.

	PR c++/99599
	PR c++/120185

gcc/cp/ChangeLog:

	* class.cc (type_has_converting_constructor): Handle null parm.
	* pt.cc (fn_type_unification): Skip early non-dep checking if
	no concepts.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/concepts-nondep6.C: New test.
---

diff --git a/gcc/cp/class.cc b/gcc/cp/class.cc
index 370bfa35f9e..2764bb52ddd 100644
--- a/gcc/cp/class.cc
+++ b/gcc/cp/class.cc
@@ -5744,6 +5744,9 @@ type_has_converting_constructor (tree t)
     {
       tree fn = *iter;
       tree parm = FUNCTION_FIRST_USER_PARMTYPE (fn);
+      if (parm == NULL_TREE)
+	/* Varargs.  */
+	return true;
       if (parm == void_list_node
 	  || !sufficient_parms_p (TREE_CHAIN (parm)))
 	/* Can't accept a single argument, so won't be considered for
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 0694c28cde3..09f74a2814b 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -23254,7 +23254,7 @@ fn_type_unification (tree fn,
      conversions that we know are not going to induce template instantiation
      (PR99599).  */
   if (strict == DEDUCE_CALL
-      && incomplete
+      && incomplete && flag_concepts
       && check_non_deducible_conversions (parms, args, nargs, fn, strict, flags,
 					  convs, explain_p,
 					  /*noninst_only_p=*/true))
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-nondep6.C b/gcc/testsuite/g++.dg/cpp2a/concepts-nondep6.C
new file mode 100644
index 00000000000..7adf6ecfb86
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-nondep6.C
@@ -0,0 +1,12 @@
+// PR c++/120185
+
+struct A {
+  A(...);
+};
+
+template <class T> void f(A, T) { }
+
+int main()
+{
+  f(42, 24);
+}