c++: Fix up attribute rollbacks in cp_parser_statement

During the OpenMP directives using C++ attribute syntax work, I've noticed
that cp_parser_statement when parsing various block declarations that do
not allow attribute-specifier-seq at the start rolls back the attributes
only if std_attrs is non-NULL (i.e. some attributes have been parsed),
but doesn't roll back if some tokens were parsed as attribute-specifier-seq,
but didn't yield any attributes (e.g. [[]][[]][[]][[]]), which means
we accept those empty attributes even in places where they don't appear
in the grammar.

The following patch fixes that by instead checking if there are any
tokens to roll back.  This makes the parsing handle the first
function the same as the second one (where some attribute appears).

The testcase contains two xfails, using namespace ... apparently
allows attributes at the start and the attributes shall appeartain to
using in that case.  To be fixed incrementally.

2021-07-30  Jakub Jelinek  <jakub@redhat.com>

	* parser.c (cp_parser_statement): Rollback attributes not just
	when std_attrs is non-NULL, but whenever
	cp_parser_std_attribute_spec_seq parsed any tokens.

	* g++.dg/cpp0x/gen-attrs-76.C: New test.

(cherry picked from commit 0ba2003cf306aa98b6ec91c9d849ab9bafcf17c2)

diff --git a/gcc/cp/ChangeLog.omp b/gcc/cp/ChangeLog.omp
index bdf818a78e6f639af00c9c8f44391790e37052d7..c7c267aae693324fadf3c166cbf66af4363395ab 100644 (file)
--- a/gcc/cp/ChangeLog.omp
+++ b/gcc/cp/ChangeLog.omp
@@ -1,3 +1,12 @@
+2021-07-30  Tobias Burnus  <tobias@codesourcery.com>
+
+       Backported from master:
+       2021-07-30  Jakub Jelinek  <jakub@redhat.com>
+
+       * parser.c (cp_parser_statement): Rollback attributes not just
+       when std_attrs is non-NULL, but whenever
+       cp_parser_std_attribute_spec_seq parsed any tokens.
+
 2021-07-30  Tobias Burnus  <tobias@codesourcery.com>
 
        Backported from master:

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 8869a4884b71fc987f6126ed99e681364f66af9c..0e62c5b69fdd3ef75a2bc7c145506cb7be38bff7 100644 (file)
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -11878,6 +11878,7 @@ cp_parser_statement (cp_parser* parser, tree in_statement_expr,
   cp_token *token;
   location_t statement_location, attrs_loc;
   bool in_omp_attribute_pragma = parser->lexer->in_omp_attribute_pragma;
+  bool has_std_attrs;
 
  restart:
   if (if_p != NULL)
@@ -11886,7 +11887,8 @@ cp_parser_statement (cp_parser* parser, tree in_statement_expr,
   statement = NULL_TREE;
 
   saved_token_sentinel saved_tokens (parser->lexer);
-  attrs_loc = cp_lexer_peek_token (parser->lexer)->location;
+  token = cp_lexer_peek_token (parser->lexer);
+  attrs_loc = token->location;
   if (c_dialect_objc ())
     /* In obj-c++, seeing '[[' might be the either the beginning of
        c++11 attributes, or a nested objc-message-expression.  So
@@ -11900,6 +11902,7 @@ cp_parser_statement (cp_parser* parser, tree in_statement_expr,
       if (!cp_parser_parse_definitely (parser))
        std_attrs = NULL_TREE;
     }
+  has_std_attrs = cp_lexer_peek_token (parser->lexer) != token;
 
   if (std_attrs && (flag_openmp || flag_openmp_simd))
     std_attrs = cp_parser_handle_statement_omp_attributes (parser, std_attrs);
@@ -11968,7 +11971,7 @@ cp_parser_statement (cp_parser* parser, tree in_statement_expr,
 
        case RID_NAMESPACE:
          /* This must be a namespace alias definition.  */
-         if (std_attrs != NULL_TREE)
+         if (has_std_attrs)
            {
              /* Attributes should be parsed as part of the
                 declaration, so let's un-parse them.  */
@@ -12073,7 +12076,7 @@ cp_parser_statement (cp_parser* parser, tree in_statement_expr,
     {
       if (cp_lexer_next_token_is_not (parser->lexer, CPP_SEMICOLON))
        {
-         if (std_attrs != NULL_TREE)
+         if (has_std_attrs)
            /* Attributes should be parsed as part of the declaration,
               so let's un-parse them.  */
            saved_tokens.rollback();
@@ -12085,7 +12088,7 @@ cp_parser_statement (cp_parser* parser, tree in_statement_expr,
          if (cp_parser_parse_definitely (parser))
            return;
          /* It didn't work, restore the post-attribute position.  */
-         if (std_attrs)
+         if (has_std_attrs)
            cp_lexer_set_token_position (parser->lexer, statement_token);
        }
       /* All preceding labels have been parsed at this point.  */

diff --git a/gcc/testsuite/ChangeLog.omp b/gcc/testsuite/ChangeLog.omp
index 3e427ca7bc2b41369b5deb99571b4286884c44bc..6437bc32db8e43e0ea957ebca70888e224d85c2d 100644 (file)
--- a/gcc/testsuite/ChangeLog.omp
+++ b/gcc/testsuite/ChangeLog.omp
@@ -1,3 +1,10 @@
+2021-07-30  Tobias Burnus  <tobias@codesourcery.com>
+
+       Backported from master:
+       2021-07-30  Jakub Jelinek  <jakub@redhat.com>
+
+       * g++.dg/cpp0x/gen-attrs-76.C: New test.
+
 2021-07-30  Tobias Burnus  <tobias@codesourcery.com>
 
        Backported from master:

diff --git a/gcc/testsuite/g++.dg/cpp0x/gen-attrs-76.C b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-76.C
new file mode 100644 (file)
index 0000000..cbda8de
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-76.C
@@ -0,0 +1,31 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wno-attributes" }
+
+namespace N {}
+namespace O { typedef int T; };
+
+void
+foo ()
+{
+  [[]] asm ("");                               // { dg-error "expected" }
+  [[]] __extension__ asm ("");                 // { dg-error "expected" }
+  __extension__ [[]] asm ("");                 // { dg-error "expected" }
+  [[]] namespace M = ::N;                      // { dg-error "expected" }
+  [[]] using namespace N;                      // { dg-bogus "expected" "" { xfail *-*-* } }
+  [[]] using O::T;                             // { dg-error "expected" }
+  [[]] __label__ foo;                          // { dg-error "expected" }
+  [[]] static_assert (true, "");               // { dg-error "expected" }
+}
+
+void
+bar ()
+{
+  [[gnu::unused]] asm ("");                    // { dg-error "expected" }
+  [[gnu::unused]] __extension__ asm ("");      // { dg-error "expected" }
+  __extension__ [[gnu::unused]] asm ("");      // { dg-error "expected" }
+  [[gnu::unused]] namespace M = ::N;           // { dg-error "expected" }
+  [[gnu::unused]] using namespace N;           // { dg-bogus "expected" "" { xfail *-*-* } }
+  [[gnu::unused]] using O::T;                  // { dg-error "expected" }
+  [[gnu::unused]] __label__ foo;               // { dg-error "expected" }
+  [[gnu::unused]] static_assert (true, "");    // { dg-error "expected" }
+}