c++: Parse and ignore attributes on base specifiers [PR110345]

For C++ 26 P2552R3 I went through all the spots (except modules) where
attribute-specifier-seq appears in the grammar and tried to construct
a testcase in all those spots, for now for [[deprecated]] attribute.

This is the third issue I found.

https://eel.is/c++draft/class.derived#general-1 has attribute-specifier-seq
at the start of base-specifier.  The following patch parses it there and
warns about those.

2024-08-20  Jakub Jelinek  <jakub@redhat.com>

	PR c++/110345
	* parser.cc (cp_parser_base_specifier): Parse standard attributes
	at the start and emit a warning if there are any non-ignored ones.

	* g++.dg/cpp0x/gen-attrs-83.C: New test.

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index c43889803482442087fd5f08854bdb56cdfabf74..28ebf2beb60a47463ead7f587a1e5e6427b8bc6b 100644 (file)
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -28995,11 +28995,12 @@ cp_parser_base_clause (cp_parser* parser)
 /* Parse a base-specifier.
 
    base-specifier:
-     :: [opt] nested-name-specifier [opt] class-name
-     virtual access-specifier [opt] :: [opt] nested-name-specifier
-       [opt] class-name
-     access-specifier virtual [opt] :: [opt] nested-name-specifier
-       [opt] class-name
+     attribute-specifier-seq [opt] :: [opt] nested-name-specifier [opt]
+       class-name
+     attribute-specifier-seq [opt] virtual access-specifier [opt] :: [opt]
+       nested-name-specifier [opt] class-name
+     attribute-specifier-seq [opt] access-specifier virtual [opt] :: [opt]
+       nested-name-specifier [opt] class-name
 
    Returns a TREE_LIST.  The TREE_PURPOSE will be one of
    ACCESS_{DEFAULT,PUBLIC,PROTECTED,PRIVATE}_[VIRTUAL]_NODE to
@@ -29017,6 +29018,12 @@ cp_parser_base_specifier (cp_parser* parser)
   bool class_scope_p, template_p;
   tree access = access_default_node;
   tree type;
+  location_t attrs_loc = cp_lexer_peek_token (parser->lexer)->location;
+  tree std_attrs = cp_parser_std_attribute_spec_seq (parser);
+
+  if (std_attrs != NULL_TREE && any_nonignored_attribute_p (std_attrs))
+    warning_at (attrs_loc, OPT_Wattributes,
+               "attributes on base specifiers are ignored");
 
   /* Process the optional `virtual' and `access-specifier'.  */
   while (!done)

diff --git a/gcc/testsuite/g++.dg/cpp0x/gen-attrs-83.C b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-83.C
new file mode 100644 (file)
index 0000000..0ff1965
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-83.C
@@ -0,0 +1,10 @@
+// { dg-do compile { target c++11 } }
+
+struct A {};
+struct B {};
+struct C {};
+struct D : [[]] [[]] A,
+          [[]] virtual public B, [[]] [[]] [[]] public virtual C {};
+struct E : [[gnu::deprecated]] A,                      // { dg-warning "attributes on base specifiers are ignored" }
+          [[gnu::deprecated]] virtual public B,        // { dg-warning "attributes on base specifiers are ignored" }
+          [[gnu::deprecated]] public virtual C {};     // { dg-warning "attributes on base specifiers are ignored" }