c: Update __has_c_attribute values for C2x

WG14 decided that __has_c_attribute should return the same value
(equal to the intended __STDC_VERSION__ value) for all standard
attributes in C2x, with values associated with when an attribute was
added to the working draft (or had semantics added or changed in the
working draft) only being used in earlier stages of development of
that draft.  The intent is that the values for existing attributes
increase in future standard versions only if there are new features /
semantic changes for those attributes.  Implement this change for GCC.

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

gcc/c-family/
	* c-lex.cc (c_common_has_attribute): Use 202311 as
	__has_c_attribute return for all C2x attributes.

gcc/testsuite/
	* gcc.dg/c2x-has-c-attribute-2.c: Expect 202311L return value from
	__has_c_attribute for all C2x attributes.

2 files changed, 20 insertions, 24 deletions

diff --git a/gcc/c-family/c-lex.cc b/gcc/c-family/c-lex.cc
index 6eb0fae..dcd061c 100644
--- a/gcc/c-family/c-lex.cc
+++ b/gcc/c-family/c-lex.cc
@@ -392,17 +392,13 @@ c_common_has_attribute (cpp_reader *pfile, bool std_syntax)
 	    }
 	  else
 	    {
-	      if (is_attribute_p ("deprecated", attr_name))
-		result = 201904;
-	      else if (is_attribute_p ("fallthrough", attr_name))
-		result = 201910;
-	      else if (is_attribute_p ("nodiscard", attr_name))
-		result = 202003;
-	      else if (is_attribute_p ("maybe_unused", attr_name))
-		result = 202106;
-	      else if (is_attribute_p ("noreturn", attr_name)
-		       || is_attribute_p ("_Noreturn", attr_name))
-		result = 202202;
+	      if (is_attribute_p ("deprecated", attr_name)
+		  || is_attribute_p ("fallthrough", attr_name)
+		  || is_attribute_p ("maybe_unused", attr_name)
+		  || is_attribute_p ("nodiscard", attr_name)
+		  || is_attribute_p ("noreturn", attr_name)
+		  || is_attribute_p ("_Noreturn", attr_name))
+		result = 202311;
 	    }
 	  if (result)
 	    attr_name = NULL_TREE;
diff --git a/gcc/testsuite/gcc.dg/c2x-has-c-attribute-2.c b/gcc/testsuite/gcc.dg/c2x-has-c-attribute-2.c
index 3c34ab6..dc92b95 100644
--- a/gcc/testsuite/gcc.dg/c2x-has-c-attribute-2.c
+++ b/gcc/testsuite/gcc.dg/c2x-has-c-attribute-2.c
@@ -2,56 +2,56 @@
 /* { dg-do preprocess } */
 /* { dg-options "-std=c2x -pedantic-errors" } */
 
-#if __has_c_attribute ( nodiscard ) != 202003L
+#if __has_c_attribute ( nodiscard ) != 202311L
 #error "bad result for nodiscard"
 #endif
 
-#if __has_c_attribute ( __nodiscard__ ) != 202003L
+#if __has_c_attribute ( __nodiscard__ ) != 202311L
 #error "bad result for __nodiscard__"
 #endif
 
-#if __has_c_attribute(maybe_unused) != 202106L
+#if __has_c_attribute(maybe_unused) != 202311L
 #error "bad result for maybe_unused"
 #endif
 
-#if __has_c_attribute(__maybe_unused__) != 202106L
+#if __has_c_attribute(__maybe_unused__) != 202311L
 #error "bad result for __maybe_unused__"
 #endif
 
-#if __has_c_attribute (deprecated) != 201904L
+#if __has_c_attribute (deprecated) != 202311L
 #error "bad result for deprecated"
 #endif
 
-#if __has_c_attribute (__deprecated__) != 201904L
+#if __has_c_attribute (__deprecated__) != 202311L
 #error "bad result for __deprecated__"
 #endif
 
-#if __has_c_attribute (fallthrough) != 201910L
+#if __has_c_attribute (fallthrough) != 202311L
 #error "bad result for fallthrough"
 #endif
 
-#if __has_c_attribute (__fallthrough__) != 201910L
+#if __has_c_attribute (__fallthrough__) != 202311L
 #error "bad result for __fallthrough__"
 #endif
 
-#if __has_c_attribute (noreturn) != 202202L
+#if __has_c_attribute (noreturn) != 202311L
 #error "bad result for noreturn"
 #endif
 
-#if __has_c_attribute (__noreturn__) != 202202L
+#if __has_c_attribute (__noreturn__) != 202311L
 #error "bad result for __noreturn__"
 #endif
 
-#if __has_c_attribute (_Noreturn) != 202202L
+#if __has_c_attribute (_Noreturn) != 202311L
 #error "bad result for _Noreturn"
 #endif
 
-#if __has_c_attribute (___Noreturn__) != 202202L
+#if __has_c_attribute (___Noreturn__) != 202311L
 #error "bad result for ___Noreturn__"
 #endif
   
 /* Macros in the attribute name are expanded.  */
 #define foo deprecated
-#if __has_c_attribute (foo) != 201904L
+#if __has_c_attribute (foo) != 202311L
 #error "bad result for foo"
 #endif