c: New C2x keywords

C2x follows C++ in making alignas, alignof, bool, false,
static_assert, thread_local and true keywords; implement this
accordingly.  This implementation makes them normal keywords in C2x
mode just like any other keyword (C2x leaves open the possibility of
implementation using predefined macros instead - thus, there aren't
any testcases asserting that they aren't macros).  As in C++ and
previous versions of C, true and false are handled like signed 1 and 0
in #if (there was an intermediate state in some C2x drafts where they
had different macro expansions that were unsigned in #if).

Bootstrapped with no regressions for x86_64-pc-linux-gnu.

As with the removal of unprototyped functions, this change has a high
risk of breaking some old code and people doing GNU/Linux distribution
builds may wish to see how much is broken in a build with a -std=gnu2x
default.

gcc/
	* ginclude/stdalign.h [defined __STDC_VERSION__ &&
	__STDC_VERSION__ > 201710L]: Disable all content.
	* ginclude/stdbool.h [defined __STDC_VERSION__ && __STDC_VERSION__
	> 201710L] (bool, true, false): Do not define.

gcc/c-family/
	* c-common.cc (c_common_reswords): Use D_C2X instead of D_CXXONLY
	for alignas, alignof, bool, false, static_assert, thread_local and
	true.

gcc/c/
	* c-parser.cc (c_parser_static_assert_declaration_no_semi)
	(c_parser_alignas_specifier, c_parser_alignof_expression): Allow
	for C2x spellings of keywords.
	(c_parser_postfix_expression): Handle RID_TRUE and RID_FALSE.

gcc/testsuite/
	* gcc.dg/c11-keywords-1.c, gcc.dg/c2x-align-1.c,
	gcc.dg/c2x-align-6.c, gcc.dg/c2x-bool-2.c,
	gcc.dg/c2x-static-assert-3.c, gcc.dg/c2x-static-assert-4.c,
	gcc.dg/c2x-thread-local-1.c: New tests.
	* gcc.dg/c2x-bool-1.c: Update expectations.

libcpp/
	* include/cpplib.h (struct cpp_options): Add true_false.
	* expr.cc (eval_token): Check true_false not cplusplus to
	determine whether to handle true and false keywords.
	* init.cc (struct lang_flags): Add true_false.
	(lang_defaults): Update.
	(cpp_set_lang): Set true_false.

1 files changed, 22 insertions, 8 deletions

diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
index 72db5b5..d134448 100644
--- a/gcc/c/c-parser.cc
+++ b/gcc/c/c-parser.cc
@@ -2630,13 +2630,14 @@ c_parser_static_assert_declaration_no_semi (c_parser *parser)
   tree string = NULL_TREE;
 
   gcc_assert (c_parser_next_token_is_keyword (parser, RID_STATIC_ASSERT));
+  tree spelling = c_parser_peek_token (parser)->value;
   assert_loc = c_parser_peek_token (parser)->location;
   if (flag_isoc99)
     pedwarn_c99 (assert_loc, OPT_Wpedantic,
-		 "ISO C99 does not support %<_Static_assert%>");
+		 "ISO C99 does not support %qE", spelling);
   else
     pedwarn_c99 (assert_loc, OPT_Wpedantic,
-		 "ISO C90 does not support %<_Static_assert%>");
+		 "ISO C90 does not support %qE", spelling);
   c_parser_consume_token (parser);
   matching_parens parens;
   if (!parens.require_open (parser))
@@ -2667,7 +2668,7 @@ c_parser_static_assert_declaration_no_semi (c_parser *parser)
        new C2X feature of _Static_assert.  */
     pedwarn_c11 (assert_loc, OPT_Wpedantic,
 		 "ISO C11 does not support omitting the string in "
-		 "%<_Static_assert%>");
+		 "%qE", spelling);
   parens.require_close (parser);
 
   if (!INTEGRAL_TYPE_P (TREE_TYPE (value)))
@@ -3774,13 +3775,14 @@ c_parser_alignas_specifier (c_parser * parser)
   tree ret = error_mark_node;
   location_t loc = c_parser_peek_token (parser)->location;
   gcc_assert (c_parser_next_token_is_keyword (parser, RID_ALIGNAS));
+  tree spelling = c_parser_peek_token (parser)->value;
   c_parser_consume_token (parser);
   if (flag_isoc99)
     pedwarn_c99 (loc, OPT_Wpedantic,
-		 "ISO C99 does not support %<_Alignas%>");
+		 "ISO C99 does not support %qE", spelling);
   else
     pedwarn_c99 (loc, OPT_Wpedantic,
-		 "ISO C90 does not support %<_Alignas%>");
+		 "ISO C90 does not support %qE", spelling);
   matching_parens parens;
   if (!parens.require_open (parser))
     return ret;
@@ -8399,10 +8401,12 @@ c_parser_alignof_expression (c_parser *parser)
   location_t end_loc;
   tree alignof_spelling = c_parser_peek_token (parser)->value;
   gcc_assert (c_parser_next_token_is_keyword (parser, RID_ALIGNOF));
-  bool is_c11_alignof = strcmp (IDENTIFIER_POINTER (alignof_spelling),
-				"_Alignof") == 0;
+  bool is_c11_alignof = (strcmp (IDENTIFIER_POINTER (alignof_spelling),
+				"_Alignof") == 0
+			 || strcmp (IDENTIFIER_POINTER (alignof_spelling),
+				    "alignof") == 0);
   /* A diagnostic is not required for the use of this identifier in
-     the implementation namespace; only diagnose it for the C11
+     the implementation namespace; only diagnose it for the C11 or C2X
      spelling because of existing code using the other spellings.  */
   if (is_c11_alignof)
     {
@@ -10272,6 +10276,16 @@ c_parser_postfix_expression (c_parser *parser)
 	  pedwarn_c11 (loc, OPT_Wpedantic,
 		       "ISO C does not support %qs before C2X", "nullptr");
 	  break;
+	case RID_TRUE:
+	  c_parser_consume_token (parser);
+	  expr.value = boolean_true_node;
+	  set_c_expr_source_range (&expr, tok_range);
+	  break;
+	case RID_FALSE:
+	  c_parser_consume_token (parser);
+	  expr.value = boolean_false_node;
+	  set_c_expr_source_range (&expr, tok_range);
+	  break;
 	default:
 	  c_parser_error (parser, "expected expression");
 	  expr.set_error ();