On 11/1/22 13:01, Marek Polacek wrote:
It seems wrong to issue a -Wignored-qualifiers warning for code like:
static_assert(!is_same_v<void(*)(), const void(*)()>);
because there the qualifier matters. Likewise in template
specialization:
template<typename T> struct S { };
template<> struct S<void(*)()> { };
template<> struct S<const void(*)()> { }; // OK, not a redefinition
I'm of the mind that we should disable the warning for template
arguments, as in the patch below.
Hmm, I'm not sure why we would want to treat template arguments
differently from other type-ids. Maybe only warn if funcdecl_p?
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
PR c++/107492
gcc/cp/ChangeLog:
* parser.cc (cp_parser_template_type_arg): Suppress -Wignored-qualifiers
warning.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wignored-qualifiers3.C: New test.
---
gcc/cp/parser.cc | 4 ++++
gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C | 12 ++++++++++++
2 files changed, 16 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index e0e3cf3eaf6..54ad4b98ed3 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -24334,6 +24334,10 @@ cp_parser_template_type_arg (cp_parser *parser)
const char *saved_message = parser->type_definition_forbidden_message;
parser->type_definition_forbidden_message
= G_("types may not be defined in template arguments");
+ /* It's wrong to issue a -Wignored-qualifiers warning for
+ static_assert(!is_same_v<void(*)(), const void(*)()>);
+ because there the qualifier matters. */
+ warning_sentinel w (warn_ignored_qualifiers);
r = cp_parser_type_id_1 (parser, CP_PARSER_FLAGS_NONE, true, false, NULL);
parser->type_definition_forbidden_message = saved_message;
if (cxx_dialect >= cxx14 && !flag_concepts && type_uses_auto (r))
diff --git a/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
b/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
new file mode 100644
index 00000000000..5696feaaefe
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
@@ -0,0 +1,12 @@
+// PR c++/107492
+// { dg-do compile { target c++14 } }
+// { dg-additional-options "-Wignored-qualifiers" }
+
+template<typename T> struct S { };
+template<> struct S<void(*)()> { };
+template<> struct S<const void(*)()> { }; // { dg-bogus "ignored" }
+
+template<typename T, typename U> constexpr bool is_same_v = false;
+template<typename T> constexpr bool is_same_v<T, T> = true;
+
+static_assert( ! is_same_v< void(*)(), const void(*)() >, ""); // { dg-bogus
"ignored" }
base-commit: e7310e24b1c0ca67b1bb507c1330b2bf39e59e32
