Patchwork C++0x, implement final on classes

login
register
mail settings
Submitter ville
Date May 14, 2011, 2:56 p.m.
Message ID <87liy9nxf1.wl%ville@ville-laptop>
Download mbox | patch
Permalink /patch/95559/
State New
Headers show

Comments

ville - May 14, 2011, 2:56 p.m.
At Sat, 14 May 2011 09:01:39 +0200,
Paolo Carlini wrote:
> ... I'm wondering if wouldn't be more appropriate for the new testcase to be in /cpp0x, with a name like final.C

There are probably other tests there that need moving too,
if such moving is done. I don't have a strong opinion
either way, but maybe the moving should be done separately?

The last patch contained a ligature in the grammar comment 
for class-virt-specifier.. fixed below.
Jason Merrill - May 14, 2011, 4:41 p.m.
On 05/14/2011 10:56 AM, Ville Voutilainen wrote:
> At Sat, 14 May 2011 09:01:39 +0200,
> Paolo Carlini wrote:
>> ... I'm wondering if wouldn't be more appropriate for the new testcase to be in /cpp0x, with a name like final.C
>
> There are probably other tests there that need moving too,
> if such moving is done. I don't have a strong opinion
> either way, but maybe the moving should be done separately?

Paolo is right, C++0x tests go in cpp0x.  I'll move this and your 
earlier one.

Jason
ville - May 14, 2011, 4:42 p.m.
On 14 May 2011 19:41, Jason Merrill <jason@redhat.com> wrote:
> Paolo is right, C++0x tests go in cpp0x.  I'll move this and your earlier
> one.

Duly noted, I'll keep that in mind for subsequent ones. Is the patch
otherwise ok?
Jason Merrill - May 14, 2011, 6:15 p.m.
On 05/14/2011 12:42 PM, Ville Voutilainen wrote:
> On 14 May 2011 19:41, Jason Merrill<jason@redhat.com>  wrote:
>> Paolo is right, C++0x tests go in cpp0x.  I'll move this and your earlier
>> one.
>
> Duly noted, I'll keep that in mind for subsequent ones. Is the patch
> otherwise ok?

Yes, and I've applied it.

Jason
ville - May 14, 2011, 6:19 p.m.
On 14 May 2011 21:15, Jason Merrill <jason@redhat.com> wrote:
> On 05/14/2011 12:42 PM, Ville Voutilainen wrote:
>> Duly noted, I'll keep that in mind for subsequent ones. Is the patch
>> otherwise ok?
> Yes, and I've applied it.

Cool, thanks! I'm not quite sure whether there are ambiguities in the case
of elaborate-specifiers, but I suppose those can be fixed later. Should these
facilities be somehow flagged 0x-only? I haven't done that at all..

Somebody should probably update the C++0x status page, and refer to N3206
rather than to N2928 for explicit virtual overrides, and mark it done?
Jason Merrill - May 14, 2011, 10:49 p.m.
On 05/14/2011 02:19 PM, Ville Voutilainen wrote:
> Cool, thanks! I'm not quite sure whether there are ambiguities in the case
> of elaborate-specifiers, but I suppose those can be fixed later.

Good point.  In the case that 
!cp_parser_next_token_starts_class_definition_p, we should rewind to 
before what we parsed as virt-specifiers.

> Should these
> facilities be somehow flagged 0x-only? I haven't done that at all..

Yes, we should maybe_warn_cpp0x about them.

> Somebody should probably update the C++0x status page, and refer to N3206
> rather than to N2928 for explicit virtual overrides, and mark it done?

Will do.

Jason
Jason Merrill - May 14, 2011, 10:52 p.m.
On 05/14/2011 06:49 PM, Jason Merrill wrote:
> On 05/14/2011 02:19 PM, Ville Voutilainen wrote:
>> Cool, thanks! I'm not quite sure whether there are ambiguities in the
>> case
>> of elaborate-specifiers, but I suppose those can be fixed later.
>
> Good point. In the case that
> !cp_parser_next_token_starts_class_definition_p, we should rewind to
> before what we parsed as virt-specifiers.

cp_lexer_token_position and cp_lexer_set_token_position should be useful 
for this.

Jason

Patch

diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index 293dd1c..40a7643 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -1268,6 +1268,10 @@  check_bases (tree t,
 
       gcc_assert (COMPLETE_TYPE_P (basetype));
 
+      if (CLASSTYPE_FINAL (basetype))
+        error ("cannot derive from %<final%> base %qT in derived type %qT",
+               basetype, t);
+
       /* If any base class is non-literal, so is the derived class.  */
       if (!CLASSTYPE_LITERAL_P (basetype))
         CLASSTYPE_LITERAL_P (t) = false;
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 1705232..901a17d 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -1321,6 +1321,7 @@  struct GTY(()) lang_type_class {
   unsigned has_complex_move_ctor : 1;
   unsigned has_complex_move_assign : 1;
   unsigned has_constexpr_ctor : 1;
+  unsigned is_final : 1;
 
   /* When adding a flag here, consider whether or not it ought to
      apply to a template instance if it applies to the template.  If
@@ -1329,7 +1330,7 @@  struct GTY(()) lang_type_class {
   /* There are some bits left to fill out a 32-bit word.  Keep track
      of this by updating the size of this bitfield whenever you add or
      remove a flag.  */
-  unsigned dummy : 3;
+  unsigned dummy : 2;
 
   tree primary_base;
   VEC(tree_pair_s,gc) *vcall_indices;
@@ -1437,6 +1438,11 @@  struct GTY((variable_size)) lang_type {
 #define CLASSTYPE_LAZY_DESTRUCTOR(NODE) \
   (LANG_TYPE_CLASS_CHECK (NODE)->lazy_destructor)
 
+/* Nonzero means that NODE (a class type) is final */
+#define CLASSTYPE_FINAL(NODE) \
+  (LANG_TYPE_CLASS_CHECK (NODE)->is_final)
+
+
 /* Nonzero means that this _CLASSTYPE node overloads operator=(X&).  */
 #define TYPE_HAS_COPY_ASSIGN(NODE) (LANG_TYPE_CLASS_CHECK (NODE)->has_copy_assign)
 
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index fa6cd83..a77d4ff 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -17082,10 +17082,13 @@  cp_parser_class_specifier (cp_parser* parser)
 
    class-head:
      class-key identifier [opt] base-clause [opt]
-     class-key nested-name-specifier identifier base-clause [opt]
+     class-key nested-name-specifier identifier class-virt-specifier [opt] base-clause [opt]
      class-key nested-name-specifier [opt] template-id
        base-clause [opt]
 
+   class-virt-specifier:
+     final
+
    GNU Extensions:
      class-key attributes identifier [opt] base-clause [opt]
      class-key attributes nested-name-specifier identifier base-clause [opt]
@@ -17117,6 +17120,7 @@  cp_parser_class_head (cp_parser* parser,
   tree id = NULL_TREE;
   tree type = NULL_TREE;
   tree attributes;
+  cp_virt_specifiers virt_specifiers = VIRT_SPEC_UNSPECIFIED;
   bool template_id_p = false;
   bool qualified_p = false;
   bool invalid_nested_name_p = false;
@@ -17260,8 +17264,11 @@  cp_parser_class_head (cp_parser* parser,
   pop_deferring_access_checks ();
 
   if (id)
-    cp_parser_check_for_invalid_template_id (parser, id,
-					     type_start_token->location);
+    {
+      cp_parser_check_for_invalid_template_id (parser, id,
+                                               type_start_token->location);
+      virt_specifiers = cp_parser_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
@@ -17277,6 +17284,13 @@  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)
     {
@@ -17493,6 +17507,8 @@  cp_parser_class_head (cp_parser* parser,
   if (type)
     DECL_SOURCE_LOCATION (TYPE_NAME (type)) = type_start_token->location;
   *attributes_p = attributes;
+  if (type && (virt_specifiers & VIRT_SPEC_FINAL))
+    CLASSTYPE_FINAL (type) = 1;
  out:
   parser->colon_corrects_to_scope_p = saved_colon_corrects_to_scope_p;
   return type;
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 5e24977..5e059e0 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -8209,6 +8209,7 @@  instantiate_class_template_1 (tree type)
       CLASSTYPE_VISIBILITY_SPECIFIED (type) = 1;
       CLASSTYPE_VISIBILITY (type) = CLASSTYPE_VISIBILITY (pattern);
     }
+  CLASSTYPE_FINAL (type) = CLASSTYPE_FINAL (pattern);
 
   pbinfo = TYPE_BINFO (pattern);
 
diff --git a/gcc/testsuite/g++.dg/inherit/base4.C b/gcc/testsuite/g++.dg/inherit/base4.C
new file mode 100644
index 0000000..7f17504
--- /dev/null
+++ b/gcc/testsuite/g++.dg/inherit/base4.C
@@ -0,0 +1,47 @@ 
+// { dg-do compile }
+// { dg-options "--std=c++0x" }
+struct B1 {};
+
+struct B2 final {};
+
+struct D1 : B1 {};
+
+struct D2 : B2 {}; // { dg-error "cannot derive from 'final' base" }
+
+template<class T> struct D3 : T {};
+
+template<class T> struct D4 : T {}; // { dg-error "cannot derive from 'final' base" }
+
+template <class T> struct B3 {};
+
+template <class T> struct B4 final {};
+
+template <class T> struct B5 final {};
+
+struct undeclared<int> final { }; // { dg-error "not a template" }
+
+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 B7 override {}; // { dg-error "cannot specify 'override' for a class" }
+
+int main()
+{
+  D3<B1> d;
+  D4<B2> d2;
+  struct B2 final{}; // { dg-error "previous definition" }
+  B2 final; // { dg-error "has a previous declaration|previously declared here" }
+  B2 final2 = final;
+  struct B2 {}; // { dg-error "redefinition" }
+  struct B2 final; // { dg-error "redeclaration" }
+  struct B2 override; // { dg-error "previously declared here" }
+  struct B2 final {}; // { dg-error "redefinition" }
+  struct B2 override {}; // { dg-error "cannot specify 'override' for a class" }
+  B2 override{}; // { dg-error "redeclaration" }
+  struct foo final {}; // { dg-error "previous definition" }
+  struct foo final {}; // { dg-error "redefinition" }
+  foo final; // { dg-error "conflicting declaration" }
+}