c++: Check attributes on friend declarations [PR99032]

This patch implements [dcl.attr.grammar]/5: "If an attribute-specifier-seq
appertains to a friend declaration ([class.friend]), that declaration shall
be a definition."

This restriction applies to C++11-style attributes as well as GNU
attributes with the exception that we allow GNU attributes that require
a type, such as vector_size to continue accepting code as in attrib63.C.
There are various forms of friend declarations, we have friend
templates, C++11 extended friend declarations, and so on.  In some cases
we already ignore the attribute and warn that it was ignored.  But
certain cases weren't diagnosed, and with this patch we'll give a hard
error.  I tried hard not to emit both a warning and error and I think it
worked out.

Jason provided the cp_parser_decl_specifier_seq hunk to detect using
standard attributes in the middle of decl-specifiers, which is invalid.

Co-authored-by: Jason Merrill <jason@redhat.com>
gcc/cp/ChangeLog:

	PR c++/99032
	* cp-tree.h (any_non_type_attribute_p): Declare.
	* decl.c (grokdeclarator): Diagnose when an attribute appertains to
	a friend declaration that is not a definition.
	* decl2.c (any_non_type_attribute_p): New.
	* parser.c (cp_parser_decl_specifier_seq): Diagnose standard attributes
	in the middle of decl-specifiers.
	(cp_parser_elaborated_type_specifier): Diagnose when an attribute
	appertains to a friend declaration that is not a definition.
	(cp_parser_member_declaration): Likewise.

gcc/testsuite/ChangeLog:

	PR c++/99032
	* g++.dg/cpp0x/friend7.C: New test.
	* g++.dg/cpp0x/gen-attrs-4.C: Add dg-error.
	* g++.dg/cpp0x/gen-attrs-39-1.C: Likewise.
	* g++.dg/cpp0x/gen-attrs-74.C: New test.
	* g++.dg/ext/attrib63.C: New test.

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 122dadf976fd7d4738eb11cb198aa206bcadc484..580db914d406ea144b1a57ee2eb862aa97c289bd 100644 (file)
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6763,6 +6763,7 @@ extern tree grokbitfield (const cp_declarator *, cp_decl_specifier_seq *,
                          tree, tree, tree);
 extern tree splice_template_attributes         (tree *, tree);
 extern bool any_dependent_type_attributes_p    (tree);
+extern bool any_non_type_attribute_p           (tree);
 extern tree cp_reconstruct_complex_type                (tree, tree);
 extern bool attributes_naming_typedef_ok       (tree);
 extern void cplus_decl_attributes              (tree *, tree, int);

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index bc3928d7f85dc4e0dac1f847f7de417d014044b4..17511f09e792df43d97a4b523d067940c0343749 100644 (file)
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -13741,6 +13741,11 @@ grokdeclarator (const cp_declarator *declarator,
 
        if (friendp)
          {
+           if (attrlist && !funcdef_flag
+               /* Hack to allow attributes like vector_size on a friend.  */
+               && any_non_type_attribute_p (*attrlist))
+             error_at (id_loc, "attribute appertains to a friend "
+                       "declaration that is not a definition");
            /* Friends are treated specially.  */
            if (ctype == current_class_type)
              ;  /* We already issued a permerror.  */

diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index 89f874a32cc95f1fe9496481fd603df684951853..8e4dd6b544a3fba1915c6df1bdc3c2cc91e5cd74 100644 (file)
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -1331,6 +1331,20 @@ any_dependent_type_attributes_p (tree attrs)
   return false;
 }
 
+/* True if ATTRS contains any attribute that does not require a type.  */
+
+bool
+any_non_type_attribute_p (tree attrs)
+{
+  for (tree a = attrs; a; a = TREE_CHAIN (a))
+    {
+      const attribute_spec *as = lookup_attribute_spec (get_attribute_name (a));
+      if (as && !as->type_required)
+       return true;
+    }
+  return false;
+}
+
 /* Return true iff ATTRS are acceptable attributes to be applied in-place
    to a typedef which gives a previously unnamed class or enum a name for
    linkage purposes.  */

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 41df5dd525f3251a419998e21615ce1c763d8516..c0b579559546f85784e580c3ea8408bc8dbf0541 100644 (file)
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -15146,6 +15146,16 @@ cp_parser_decl_specifier_seq (cp_parser* parser,
       if (!found_decl_spec)
        break;
 
+      if (decl_specs->std_attributes)
+       {
+         error_at (decl_specs->locations[ds_std_attribute],
+                   "standard attributes in middle of decl-specifiers");
+         inform (decl_specs->locations[ds_std_attribute],
+                 "standard attributes must precede the decl-specifiers to "
+                 "apply to the declaration, or follow them to apply to "
+                 "the type");
+       }
+
       decl_specs->any_specifiers_p = true;
       /* After we see one decl-specifier, further decl-specifiers are
         always optional.  */
@@ -19764,11 +19774,15 @@ cp_parser_elaborated_type_specifier (cp_parser* parser,
               && ! processing_explicit_instantiation)
        warning (OPT_Wattributes,
                 "attributes ignored on template instantiation");
+      else if (is_friend && attributes)
+       error ("attribute appertains to a friend declaration that is not "
+              "a definition");
       else if (is_declaration && cp_parser_declares_only_class_p (parser))
        cplus_decl_attributes (&type, attributes, (int) ATTR_FLAG_TYPE_IN_PLACE);
       else
        warning (OPT_Wattributes,
-                "attributes ignored on elaborated-type-specifier that is not a forward declaration");
+                "attributes ignored on elaborated-type-specifier that is "
+                "not a forward declaration");
     }
 
   if (tag_type == enum_type)
@@ -26054,6 +26068,13 @@ cp_parser_member_declaration (cp_parser* parser)
                 error_at (decl_spec_token_start->location,
                           "friend declaration does not name a class or "
                           "function");
+              /* Give an error if an attribute cannot appear here, as per
+                 [dcl.attr.grammar]/5.  But not when declares_class_or_enum:
+                 we ignore attributes in elaborated-type-specifiers.  */
+              else if (!declares_class_or_enum && decl_specifiers.attributes)
+                error_at (decl_spec_token_start->location,
+                          "attribute appertains to a friend declaration "
+                          "that is not a definition");
               else
                 make_friend_class (current_class_type, type,
                                    /*complain=*/true);

diff --git a/gcc/testsuite/g++.dg/cpp0x/friend7.C b/gcc/testsuite/g++.dg/cpp0x/friend7.C
new file mode 100644 (file)
index 0000000..734b367
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/friend7.C
@@ -0,0 +1,40 @@
+// PR c++/99032
+// { dg-do compile { target c++11 } }
+
+class X { };
+template<typename T1, typename T2>
+void foo (T1, T2);
+
+struct S {
+  [[deprecated]] friend void f(); // { dg-error "attribute appertains" }
+  [[deprecated]] friend void f2() { }
+  __attribute__((deprecated)) friend void f3(); // { dg-error "attribute appertains" }
+  friend void f3 [[deprecated]] (); // { dg-error "attribute appertains" }
+  friend void f4 [[deprecated]] () { }
+  [[deprecated]] friend void; // { dg-error "attribute appertains" }
+  __attribute__((deprecated)) friend int; // { dg-error "attribute appertains" }
+  friend __attribute__((deprecated)) int; // { dg-error "attribute appertains" }
+  friend int __attribute__((deprecated)); // { dg-error "attribute appertains" }
+  [[deprecated]] friend X; // { dg-error "attribute appertains" }
+  [[deprecated]] friend class N; // { dg-warning "attribute ignored" }
+  friend class [[deprecated]] N2; // { dg-error "attribute appertains" }
+  friend class __attribute__((deprecated)) N3; // { dg-error "attribute appertains" }
+  [[deprecated]] friend void foo<>(int, int); // { dg-error "attribute appertains" }
+  [[deprecated]] friend void ::foo(int, int); // { dg-error "attribute appertains" }
+  // { dg-bogus "should have" "PR100339" { xfail *-*-* } .-1 }
+};
+
+template<typename T>
+class node { };
+
+template<typename T>
+struct A {
+  [[deprecated]] friend T; // { dg-error "attribute appertains" }
+  [[deprecated]] friend class node<T>; // { dg-warning "attribute ignored" }
+  template<typename>
+  [[deprecated]] friend class A; // { dg-warning "attribute ignored" }
+  template<typename>
+  [[deprecated]] friend void bar () { }
+  template<typename>
+  [[deprecated]] friend void baz (); // { dg-error "attribute appertains" }
+};

diff --git a/gcc/testsuite/g++.dg/cpp0x/gen-attrs-39-1.C b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-39-1.C
index 453fc01a2e994fff433d6636a70421e174c14f42..4010ba7724cf330559adcae46daa55ef595aea91 100644 (file)
--- a/gcc/testsuite/g++.dg/cpp0x/gen-attrs-39-1.C
+++ b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-39-1.C
@@ -2,7 +2,8 @@
 
 int fragile_block(void) {
   typedef 
-  [[gnu::aligned (16)]] // { dg-warning "ignored" }
+  [[gnu::aligned (16)]] // { dg-error "standard attributes in middle of decl-specifiers" }
+// { dg-warning "attribute ignored" "" { target *-*-* } .-1 }
   struct  {
     int i;
   } XmmUint16;

diff --git a/gcc/testsuite/g++.dg/cpp0x/gen-attrs-4.C b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-4.C
index b401c6908e35ea3834e17ede740e8ddd544a80b3..c120aeddf957b4d725ecdcfe8eb6ce093b3e8c2d 100644 (file)
--- a/gcc/testsuite/g++.dg/cpp0x/gen-attrs-4.C
+++ b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-4.C
@@ -13,7 +13,8 @@ int one_third [[noreturn]] [[gnu::unused]] (void);
 int [[gnu::unused]] one_half(); // { dg-warning "ignored" }
 
 static
-[[noreturn]] // { dg-warning "ignored" }
+[[noreturn]] // { dg-error "standard attributes in middle of decl-specifiers" }
+// { dg-warning "attribute ignored" "" { target *-*-* } .-1 }
 void two [[gnu::unused]] (void) {}
 
 

diff --git a/gcc/testsuite/g++.dg/cpp0x/gen-attrs-74.C b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-74.C
new file mode 100644 (file)
index 0000000..7e17bc8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-74.C
@@ -0,0 +1,10 @@
+// { dg-do compile { target c++11 } }
+// A C++11 attribute cannot appear in the middle of the decl-specifier-seq,
+// only before it (in which case it appertains to the declaration) or at
+// the end (in which case it appertains to the type).
+
+struct S {
+  friend [[deprecated]] void; // { dg-error "standard attributes in middle of decl-specifiers" }
+  friend [[deprecated]] int fn(); // { dg-error "standard attributes in middle of decl-specifiers" }
+  // { dg-warning "attribute ignored" "" { target *-*-* } .-1 }
+};

diff --git a/gcc/testsuite/g++.dg/ext/attrib63.C b/gcc/testsuite/g++.dg/ext/attrib63.C
new file mode 100644 (file)
index 0000000..e515a2b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/attrib63.C
@@ -0,0 +1,16 @@
+// { dg-do compile }
+
+#define vector __attribute__((vector_size(16)))
+class A {
+  friend vector float f();
+  __attribute__((deprecated)) friend void f2(); // { dg-error "attribute appertains" }
+  friend __attribute__((deprecated, vector_size(16))) float f3(); // { dg-error "attribute appertains" }
+  friend __attribute__((vector_size(16), deprecated)) float f4(); // { dg-error "attribute appertains" }
+};
+
+vector float vf;
+vector float
+f ()
+{
+  return vf;
+}