From: Marek Polacek <polacek@redhat.com>
To: GCC Patches <gcc-patches@gcc.gnu.org>, Jason Merrill <jason@redhat.com>
Subject: C++ PATCH for c++/88538 - braced-init-list in template-argument-list
Date: Mon, 07 Jan 2019 23:56:00 -0000 [thread overview]
Message-ID: <20190107235642.GI28316@redhat.com> (raw)
At the risk of seeming overly eager, I thought it would be reasonable to
go with the following: enabling braced-init-list as a template-argument.
As the discussion on the reflector clearly indicates, this was the intent
from the get-go.
I know, it's not a regression. But I restricted the change to C++20, and it
should strictly allow code that wasn't accepted before -- when a template
argument starts with {. Perhaps we could even drop the C++20 check.
What's your preference?
Bootstrapped/regtested on x86_64-linux, ok for trunk?
2019-01-07 Marek Polacek <polacek@redhat.com>
PR c++/88538 - braced-init-list in template-argument-list.
* parser.c (cp_parser_template_argument): Handle braced-init-list when
in C++20.
* g++.dg/cpp2a/nontype-class11.C: New test.
diff --git gcc/cp/parser.c gcc/cp/parser.c
index bca1739ace3..7de2ee28b20 100644
--- gcc/cp/parser.c
+++ gcc/cp/parser.c
@@ -16892,7 +16892,18 @@ cp_parser_template_argument (cp_parser* parser)
return argument;
}
/* It must be a non-type argument. In C++17 any constant-expression is
- allowed. */
+ allowed. In C++20, we can encounter a braced-init-list. */
+ if (cxx_dialect >= cxx2a
+ && cp_lexer_next_token_is (parser->lexer, CPP_OPEN_BRACE))
+ {
+ cp_parser_parse_tentatively (parser);
+ bool expr_non_constant_p;
+ argument = cp_parser_braced_list (parser, &expr_non_constant_p);
+ if (cp_parser_parse_definitely (parser))
+ /* Yup, it was a braced-init-list. */
+ return argument;
+ }
+
if (cxx_dialect > cxx14)
goto general_expr;
diff --git gcc/testsuite/g++.dg/cpp2a/nontype-class11.C gcc/testsuite/g++.dg/cpp2a/nontype-class11.C
new file mode 100644
index 00000000000..8a06d23904b
--- /dev/null
+++ gcc/testsuite/g++.dg/cpp2a/nontype-class11.C
@@ -0,0 +1,21 @@
+// PR c++/88538
+// { dg-do compile { target c++2a } }
+
+struct S {
+ unsigned a;
+ unsigned b;
+ constexpr S(unsigned _a, unsigned _b) noexcept: a{_a}, b{_b} { }
+};
+
+template <S p>
+void fnc()
+{
+}
+
+template<S s> struct X { };
+
+void f()
+{
+ fnc<{10,20}>();
+ X<{1, 2}> x;
+}
next reply other threads:[~2019-01-07 23:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-07 23:56 Marek Polacek [this message]
2019-01-08 2:53 ` Jason Merrill
2019-01-08 15:42 ` Marek Polacek
2019-01-08 20:46 ` Jason Merrill
2019-01-08 22:35 ` Marek Polacek
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