On 4/6/22 11:11, Patrick Palka wrote:
We were attempting to issue a -Wctad-maybe-unsupported warning even when
complain=tf_none, which led to a crash in the first testcase below and a
bogus error during SFINAE in the second testcase.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk/11?
OK.
PR c++/105143
gcc/cp/ChangeLog:
* pt.cc (do_class_deduction): Check complain before issuing a
-Wctad-maybe-unsupported warning.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/nodiscard1.C: New test.
* g++.dg/warn/Wctad-maybe-unsupported4.C: New test.
---
gcc/cp/pt.cc | 2 +-
gcc/testsuite/g++.dg/cpp2a/nodiscard1.C | 13 +++++++++++++
.../g++.dg/warn/Wctad-maybe-unsupported4.C | 12 ++++++++++++
3 files changed, 26 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/nodiscard1.C
create mode 100644 gcc/testsuite/g++.dg/warn/Wctad-maybe-unsupported4.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 1f0231f70e6..1805fa68440 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -30075,7 +30075,7 @@ do_class_deduction (tree ptype, tree tmpl, tree init,
/* If CTAD succeeded but the type doesn't have any explicit deduction
guides, this deduction might not be what the user intended. */
- if (fndecl != error_mark_node && !any_dguides_p)
+ if ((complain & tf_warning) && fndecl != error_mark_node && !any_dguides_p)
{
if ((!DECL_IN_SYSTEM_HEADER (fndecl)
|| global_dc->dc_warn_system_headers)
diff --git a/gcc/testsuite/g++.dg/cpp2a/nodiscard1.C
b/gcc/testsuite/g++.dg/cpp2a/nodiscard1.C
new file mode 100644
index 00000000000..c3c5094b619
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/nodiscard1.C
@@ -0,0 +1,13 @@
+// PR c++/105143
+// { dg-do compile { target c++20 } }
+// We used to crash here with "Error reporting routines re-entered".
+
+template<class...> struct A { };
+
+template<A V> using type = int;
+
+template<A V> [[nodiscard]] type<V> get();
+
+int main() {
+ get<{}>(); // { dg-warning "nodiscard" }
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wctad-maybe-unsupported4.C
b/gcc/testsuite/g++.dg/warn/Wctad-maybe-unsupported4.C
new file mode 100644
index 00000000000..0d0e2fb45eb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wctad-maybe-unsupported4.C
@@ -0,0 +1,12 @@
+// PR c++/105143
+// { dg-do compile { target c++17 } }
+// { dg-additional-options "-Werror=ctad-maybe-unsupported" }
+
+template<class...> struct A { };
+
+template<template<class...> class TT> auto f(...) -> decltype(TT()); // #1
+template<template<class...> class TT> void f(int); // #2
+
+int main() {
+ f<A>(0); // Calls #2 without issuing a -Wctad-maybe-unsupported diagnostic.
+}
