Hi,
we got a couple of duplicates of this. The issue is that things like:
struct A {};
void foo() { decltype(A()); }
are turned by finish_decltype_type, called by
cp_parser_simple_declaration via cp_parser_decl_specifier_seq, into
something like:
struct A {};
void foo() { struct A; }
and later check_tag_decl, called via shadow_tag, doesn't see anything
wrong wrt [dcl.dcl]/3, to wit doesn't see a declaration which doesn't
declare anything. "Luckily" we have declares_class_or_enum available and
we can query it to figure out whether a diagnostic is in fact in order.
Tested x86_64-linux.
Thanks,
Paolo.
PS: in fact we issue a permerror, not an error: I did some tests and I
don't think that unconditionally zeroing the type even if we end up only
emitting a warning can cause problems. But please double check, thanks!
//////////////////////////////
/cp
2013-07-07 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/51786
* parser.c (cp_parser_simple_declaration): Before calling shadow_tag
also check declares_class_or_enum.
/testsuite
2013-07-07 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/51786
* g++.dg/cpp0x/pr51786.C: New.
* g++.dg/cpp0x/auto30.C: Update.
Index: cp/parser.c
===================================================================
--- cp/parser.c (revision 200742)
+++ cp/parser.c (working copy)
@@ -11009,11 +11009,19 @@ cp_parser_simple_declaration (cp_parser* parser,
/* Issue an error message if no declarators are present, and the
decl-specifier-seq does not itself declare a class or
- enumeration. */
+ enumeration: [dcl.dcl]/3. */
if (!saw_declarator)
{
if (cp_parser_declares_only_class_p (parser))
- shadow_tag (&decl_specifiers);
+ {
+ if (!declares_class_or_enum
+ && decl_specifiers.type != error_mark_node)
+ /* Ensure an error is issued anyway when finish_decltype_type,
+ called via cp_parser_decl_specifier_seq, returns something
+ sensible (c++/51786). */
+ decl_specifiers.type = NULL_TREE;
+ shadow_tag (&decl_specifiers);
+ }
/* Perform any deferred access checks. */
perform_deferred_access_checks (tf_warning_or_error);
}
Index: testsuite/g++.dg/cpp0x/auto30.C
===================================================================
--- testsuite/g++.dg/cpp0x/auto30.C (revision 200742)
+++ testsuite/g++.dg/cpp0x/auto30.C (working copy)
@@ -6,4 +6,4 @@ struct A
auto friend struct B; // { dg-error "multiple types|can only be
specified|friend" }
};
-auto int; // { dg-error "multiple types|can only be specified for variables" }
+auto int; // { dg-error "multiple types|does not declare anything" }
Index: testsuite/g++.dg/cpp0x/pr51786.C
===================================================================
--- testsuite/g++.dg/cpp0x/pr51786.C (revision 0)
+++ testsuite/g++.dg/cpp0x/pr51786.C (working copy)
@@ -0,0 +1,8 @@
+// PR c++/51786
+// { dg-do compile { target c++11 } }
+
+enum E {};
+struct A {};
+
+void foo() { decltype(E{}); } // { dg-error "does not declare anything" }
+void bar() { decltype(A{}); } // { dg-error "does not declare anything" }
