C++ PATCH for c++/83820 - excessive attribute arguments not detected

[Marek Polacek]

While messing with [[noreturn]] I also found out that we don't detect
the case when an attribute specifier that takes no arguments contains
an attribute-argument-clause.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2019-06-16  Marek Polacek  <pola...@redhat.com>

        PR c++/83820 - excessive attribute arguments not detected.
        * parser.c (cp_parser_std_attribute): Detect excessive arguments.

        * g++.dg/cpp0x/gen-attrs-67.C: New test.

diff --git gcc/cp/parser.c gcc/cp/parser.c
index 8f5ae84670a..871bc45da63 100644
--- gcc/cp/parser.c
+++ gcc/cp/parser.c
@@ -26149,6 +26149,20 @@ cp_parser_std_attribute (cp_parser *parser, tree 
attr_ns)
     vec<tree, va_gc> *vec;
     int attr_flag = normal_attr;
 
+    /* Maybe we don't expect to see any arguments for this attribute.  */
+    const attribute_spec *as
+      = lookup_attribute_spec (TREE_PURPOSE (attribute));
+    if (as && as->max_length == 0)
+      {
+       error_at (token->location, "attribute %qE does not take any arguments",
+                 attr_id);
+       cp_parser_skip_to_closing_parenthesis (parser,
+                                              /*recovering=*/true,
+                                              /*or_comma=*/false,
+                                              /*consume_paren=*/true);
+       return error_mark_node;
+      }
+
     if (attr_ns == gnu_identifier
        && attribute_takes_identifier_p (attr_id))
       /* A GNU attribute that takes an identifier in parameter.  */
diff --git gcc/testsuite/g++.dg/cpp0x/gen-attrs-67.C 
gcc/testsuite/g++.dg/cpp0x/gen-attrs-67.C
new file mode 100644
index 00000000000..bbbedd0240a
--- /dev/null
+++ gcc/testsuite/g++.dg/cpp0x/gen-attrs-67.C
@@ -0,0 +1,11 @@
+// PR c++/83820 - excessive attribute arguments not detected.
+// { dg-do compile { target c++11 } }
+
+[[noreturn()]] void f0 (); // { dg-error "attribute .noreturn. does not take 
any arguments" }
+[[noreturn(1)]] void f1 (); // { dg-error "attribute .noreturn. does not take 
any arguments" }
+[[noreturn(1, 2)]] void f2 (); // { dg-error "attribute .noreturn. does not 
take any arguments" }
+[[maybe_unused()]] int f3(); // { dg-error "attribute .maybe_unused. does not 
take any arguments" }
+[[nodiscard()]] int f4(); // { dg-error "attribute .nodiscard. does not take 
any arguments" }
+[[gnu::noinline()]] int f5(); // { dg-error "attribute .noinline. does not 
take any arguments" }
+[[gnu::constructor]] int f6();
+[[gnu::constructor(101)]] int f7();