On 6/6/25 12:35 PM, Jakub Jelinek wrote:
Hi!
While the
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p2786r13.html#c03-compatibility-changes-for-annex-c-diff.cpp03.dcl.dcl
hunk dropped because
struct C {}; struct C {} final {};
is actually not valid C++98 (which didn't have list initialization), we
actually also reject
struct D {}; struct D {} override {};
and that IMHO is valid all the way from C++11 onwards.
I don't see how it could be, and other compilers agree with me. Since
the testcases don't put {} between the class name and the contextual
keyword, I think this is just a typo in the comment.
Especially in the light of P2786R13 adding new contextual keywords, I think
it is better to use a separate routine for parsing the
class-virt-specifier-seq (in C++11, there was export next to final),
class-virt-specifier (in C++14 to C++23) and
class-property-specifier-seq (in C++26) instead of using the same function
for virt-specifier-seq and class-property-specifier-seq.
Tested on x86_64-linux and i686-linux, ok for trunk?
2025-06-06 Jakub Jelinek <ja...@redhat.com>
PR c++/120569
* parser.cc (cp_parser_class_virt_specifier_seq_opt): New function.
Let's refer to the new non-terminal rather than the old one, both in the
name and comment of this function.
(cp_parser_class_head): Use it instead of
cp_parser_virt_specifier_seq_opt. Don't diagnose VIRT_SPEC_OVERRIDE
here. Formatting fix.
* g++.dg/cpp0x/override2.C: Expect different diagnostics with
override or duplicate final.
* g++.dg/cpp0x/override5.C: New test.
* g++.dg/cpp0x/duplicate1.C: Expect different diagnostics with
duplicate final.
--- gcc/cp/parser.cc.jj 2025-06-02 11:00:14.000000000 +0200
+++ gcc/cp/parser.cc 2025-06-06 17:20:16.344079071 +0200
@@ -28005,6 +28005,57 @@ cp_parser_class_specifier (cp_parser* pa
return type;
}
+/* Parse an (optional) class-virt-specifier-seq.
+
+ class-virt-specifier-seq:
+ class-virt-specifier class-virt-specifier-seq [opt]
+
+ class-virt-specifier:
+ final
+
+ Returns a bitmask representing the class-virt-specifiers. */
+
+static cp_virt_specifiers
+cp_parser_class_virt_specifier_seq_opt (cp_parser *parser)
+{
+ cp_virt_specifiers virt_specifiers = VIRT_SPEC_UNSPECIFIED;
+
+ while (true)
+ {
+ cp_token *token;
+ cp_virt_specifiers virt_specifier;
+
+ /* Peek at the next token. */
+ token = cp_lexer_peek_token (parser->lexer);
+ /* See if it's a class-virt-specifier. */
+ if (token->type != CPP_NAME)
+ break;
+ if (id_equal (token->u.value, "final"))
+ {
+ maybe_warn_cpp0x (CPP0X_OVERRIDE_CONTROLS);
+ virt_specifier = VIRT_SPEC_FINAL;
+ }
+ else if (id_equal (token->u.value, "__final"))
+ virt_specifier = VIRT_SPEC_FINAL;
+ else
+ break;
+
+ if (virt_specifiers & virt_specifier)
+ {
+ gcc_rich_location richloc (token->location);
+ richloc.add_fixit_remove ();
+ error_at (&richloc, "duplicate class-virt-specifier");
And here let's name the actual duplicate specifier rather refer to the
grammar.
+ cp_lexer_purge_token (parser->lexer);
+ }
+ else
+ {
+ cp_lexer_consume_token (parser->lexer);
+ virt_specifiers |= virt_specifier;
+ }
+ }
+ return virt_specifiers;
+}
+
/* Parse a class-head.
class-head:
@@ -28195,12 +28246,10 @@ cp_parser_class_head (cp_parser* parser,
pop_deferring_access_checks ();
if (id)
- {
- cp_parser_check_for_invalid_template_id (parser, id,
- class_key,
- type_start_token->location);
- }
- virt_specifiers = cp_parser_virt_specifier_seq_opt (parser);
+ cp_parser_check_for_invalid_template_id (parser, id,
+ class_key,
+ type_start_token->location);
+ virt_specifiers = cp_parser_class_virt_specifier_seq_opt (parser);
/* If it's not a `:' or a `{' then we can't really be looking at a
class-head, since a class-head only appears as part of a
@@ -28216,13 +28265,6 @@ cp_parser_class_head (cp_parser* parser,
/* At this point, we're going ahead with the class-specifier, even
if some other problem occurs. */
cp_parser_commit_to_tentative_parse (parser);
- if (virt_specifiers & VIRT_SPEC_OVERRIDE)
- {
- cp_parser_error (parser,
- "cannot specify %<override%> for a class");
- type = error_mark_node;
- goto out;
- }
/* Issue the error about the overly-qualified name now. */
if (qualified_p)
{
--- gcc/testsuite/g++.dg/cpp0x/override2.C.jj 2020-01-12 11:54:37.089403210
+0100
+++ gcc/testsuite/g++.dg/cpp0x/override2.C 2025-06-06 17:13:18.239613567
+0200
@@ -23,9 +23,9 @@ struct D5 : B3<D5> {};
struct D6 : B4<D6> {}; // { dg-error "cannot derive from 'final' base" }
-struct B6 final final {}; // { dg-error "duplicate virt-specifier" }
+struct B6 final final {}; // { dg-error "duplicate class-virt-specifier" }
-struct B7 override {}; // { dg-error "cannot specify 'override' for a class" }
+struct B7 override {}; // { dg-error "variable 'B7 override' has initializer but
incomplete type" }
namespace N
{
@@ -45,7 +45,7 @@ int main()
struct B2 final; // { dg-error "redeclaration" }
struct B2 override; // { dg-message "previously declared here" }
struct B2 final {}; // { dg-error "redefinition" }
- struct B2 override {}; // { dg-error "cannot specify 'override' for a class"
}
+ struct B2 override {}; // { dg-error "redeclaration of 'main\\\(\\\)::B2
override'" }
B2 override{}; // { dg-error "redeclaration" }
struct foo final {}; // { dg-message "previous definition" }
struct foo final {}; // { dg-error "redefinition" }
--- gcc/testsuite/g++.dg/cpp0x/override5.C.jj 2025-06-06 17:08:53.022001764
+0200
+++ gcc/testsuite/g++.dg/cpp0x/override5.C 2025-06-06 17:24:57.683354950
+0200
@@ -0,0 +1,26 @@
+// PR c++/120569
+// { dg-do compile }
+// { dg-options "" }
+// { dg-additional-options "-pedantic" { target c++14 } }
+
+namespace U {
+ struct A {};
+ struct A override {}; // { dg-warning "extended initializer lists only
available with" "" { target c++98_only } }
+}
+namespace V {
+ template <int N>
+ struct B {};
+ template <int N>
+ struct B<N> override {}; // { dg-warning "extended initializer lists only available
with" "" { target c++98_only } }
+} // { dg-warning "variable templates only available with"
"" { target c++11_down } .-1 }
+struct C {
+ struct D {};
+ struct D override {}; // { dg-warning "extended initializer lists only
available with" "" { target c++98_only } }
+}; // { dg-warning "non-static data member initializers only
available with" "" { target c++98_only } .-1 }
+namespace W {
+ struct E { struct F {}; };
+ struct E::F override {}; // { dg-warning "extended initializer lists only available
with" "" { target c++98_only } }
+}
+template <int N>
+struct V::B<N> override {}; // { dg-warning "extended initializer lists only available
with" "" { target c++98_only } }
+ // { dg-warning "variable templates only available with"
"" { target c++11_down } .-1 }
--- gcc/testsuite/g++.dg/cpp0x/duplicate1.C.jj 2020-01-14 20:02:46.724610718
+0100
+++ gcc/testsuite/g++.dg/cpp0x/duplicate1.C 2025-06-06 18:28:14.178916305
+0200
@@ -6,7 +6,7 @@ struct A
virtual void foo() const;
};
-struct B final final : A /* { dg-error "duplicate virt-specifier" }
+struct B final final : A /* { dg-error "duplicate class-virt-specifier" }
{ dg-begin-multiline-output "" }
struct B final final : A
^~~~~
Jakub
