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? 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. +} -- 2.36.0.rc0