diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 94f4868915a..f47097442eb 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -1042,7 +1042,7 @@ extern bool c_cpp_diagnostic (cpp_reader *, enum cpp_diagnostic_level,
 			      enum cpp_warning_reason, rich_location *,
 			      const char *, va_list *)
      ATTRIBUTE_GCC_DIAG(5,0);
-extern int c_common_has_attribute (cpp_reader *);
+extern int c_common_has_attribute (cpp_reader *, bool);
 extern int c_common_has_builtin (cpp_reader *);
 
 extern bool parse_optimize_options (tree, bool);
diff --git a/gcc/c-family/c-lex.c b/gcc/c-family/c-lex.c
index e81e16ddc26..6cd3df7c96f 100644
--- a/gcc/c-family/c-lex.c
+++ b/gcc/c-family/c-lex.c
@@ -300,7 +300,7 @@ get_token_no_padding (cpp_reader *pfile)
 
 /* Callback for has_attribute.  */
 int
-c_common_has_attribute (cpp_reader *pfile)
+c_common_has_attribute (cpp_reader *pfile, bool std_syntax)
 {
   int result = 0;
   tree attr_name = NULL_TREE;
@@ -319,35 +319,37 @@ c_common_has_attribute (cpp_reader *pfile)
       attr_name = get_identifier ((const char *)
 				  cpp_token_as_text (pfile, token));
       attr_name = canonicalize_attr_name (attr_name);
-      if (c_dialect_cxx ())
+      bool have_scope = false;
+      int idx = 0;
+      const cpp_token *nxt_token;
+      do
+	nxt_token = cpp_peek_token (pfile, idx++);
+      while (nxt_token->type == CPP_PADDING);
+      if (nxt_token->type == CPP_SCOPE)
 	{
-	  int idx = 0;
-	  const cpp_token *nxt_token;
-	  do
-	    nxt_token = cpp_peek_token (pfile, idx++);
-	  while (nxt_token->type == CPP_PADDING);
-	  if (nxt_token->type == CPP_SCOPE)
+	  have_scope = true;
+	  get_token_no_padding (pfile); // Eat scope.
+	  nxt_token = get_token_no_padding (pfile);
+	  if (nxt_token->type == CPP_NAME)
 	    {
-	      get_token_no_padding (pfile); // Eat scope.
-	      nxt_token = get_token_no_padding (pfile);
-	      if (nxt_token->type == CPP_NAME)
-		{
-		  tree attr_ns = attr_name;
-		  tree attr_id
-		    = get_identifier ((const char *)
-				      cpp_token_as_text (pfile, nxt_token));
-		  attr_name = build_tree_list (attr_ns, attr_id);
-		}
-	      else
-		{
-		  cpp_error (pfile, CPP_DL_ERROR,
-			     "attribute identifier required after scope");
-		  attr_name = NULL_TREE;
-		}
+	      tree attr_ns = attr_name;
+	      tree attr_id
+		= get_identifier ((const char *)
+				  cpp_token_as_text (pfile, nxt_token));
+	      attr_name = build_tree_list (attr_ns, attr_id);
 	    }
 	  else
 	    {
-	      /* Some standard attributes need special handling.  */
+	      cpp_error (pfile, CPP_DL_ERROR,
+			 "attribute identifier required after scope");
+	      attr_name = NULL_TREE;
+	    }
+	}
+      else
+	{
+	  /* Some standard attributes need special handling.  */
+	  if (c_dialect_cxx ())
+	    {
 	      if (is_attribute_p ("noreturn", attr_name))
 		result = 200809;
 	      else if (is_attribute_p ("deprecated", attr_name))
@@ -361,11 +363,20 @@ c_common_has_attribute (cpp_reader *pfile)
 		result = 201803;
 	      else if (is_attribute_p ("nodiscard", attr_name))
 		result = 201907;
-	      if (result)
-		attr_name = NULL_TREE;
 	    }
+	  else
+	    {
+	      if (is_attribute_p ("deprecated", attr_name)
+		  || is_attribute_p ("maybe_unused", attr_name)
+		  || is_attribute_p ("fallthrough", attr_name))
+		result = 201904;
+	      else if (is_attribute_p ("nodiscard", attr_name))
+		result = 202003;
+	    }
+	  if (result)
+	    attr_name = NULL_TREE;
 	}
-      if (attr_name)
+      if (attr_name && (have_scope || !std_syntax))
 	{
 	  init_attributes ();
 	  const struct attribute_spec *attr = lookup_attribute_spec (attr_name);
diff --git a/gcc/doc/cpp.texi b/gcc/doc/cpp.texi
index 33f876ab706..291e14676be 100644
--- a/gcc/doc/cpp.texi
+++ b/gcc/doc/cpp.texi
@@ -3159,6 +3159,7 @@ directive}: @samp{#if}, @samp{#ifdef} or @samp{#ifndef}.
 * Elif::
 * @code{__has_attribute}::
 * @code{__has_cpp_attribute}::
+* @code{__has_c_attribute}::
 * @code{__has_builtin}::
 * @code{__has_include}::
 @end menu
@@ -3432,8 +3433,9 @@ condition succeeds after the original @samp{#if} and all previous
 The special operator @code{__has_attribute (@var{operand})} may be used
 in @samp{#if} and @samp{#elif} expressions to test whether the attribute
 referenced by its @var{operand} is recognized by GCC.  Using the operator
-in other contexts is not valid.  In C code, @var{operand} must be
-a valid identifier.  In C++ code, @var{operand} may be optionally
+in other contexts is not valid.  In C code, if compiling for strict
+conformance to standards before C2x, @var{operand} must be
+a valid identifier.  Otherwise, @var{operand} may be optionally
 introduced by the @code{@var{attribute-scope}::} prefix.
 The @var{attribute-scope} prefix identifies the ``namespace'' within
 which the attribute is recognized.  The scope of GCC attributes is
@@ -3479,6 +3481,21 @@ information including the dates of the introduction of current standard
 attributes, see @w{@uref{https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations/,
 SD-6: SG10 Feature Test Recommendations}}.
 
+@node @code{__has_c_attribute}
+@subsection @code{__has_c_attribute}
+@cindex @code{__has_c_attribute}
+
+The special operator @code{__has_c_attribute (@var{operand})} may be
+used in @samp{#if} and @samp{#elif} expressions in C code to test
+whether the attribute referenced by its @var{operand} is recognized by
+GCC in attributes using the @samp{[[]]} syntax.  GNU attributes must
+be specified with the scope @samp{gnu} or @samp{__gnu__} with
+@code{__has_c_attribute}.  When @var{operand} designates a supported
+standard attribute it evaluates to an integer constant of the form
+@code{YYYYMM} indicating the year and month when the attribute was
+first introduced into the C standard, or when the syntax of operands
+to the attribute was extended in the C standard.
+
 @node @code{__has_builtin}
 @subsection @code{__has_builtin}
 @cindex @code{__has_builtin}
diff --git a/gcc/testsuite/gcc.dg/c2x-has-c-attribute-1.c b/gcc/testsuite/gcc.dg/c2x-has-c-attribute-1.c
new file mode 100644
index 00000000000..fe06abf99ba
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-has-c-attribute-1.c
@@ -0,0 +1,28 @@
+/* Test __has_c_attribute.  Test basic properties.  */
+/* { dg-do preprocess } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+#ifdef __has_c_attribute
+/* OK.  */
+#else
+#error "__has_c_attribute not defined"
+#endif
+
+#ifndef __has_c_attribute
+#error "__has_c_attribute not defined"
+#endif
+
+#if defined __has_c_attribute
+/* OK.  */
+#else
+#error "__has_c_attribute not defined"
+#endif
+
+#if __has_c_attribute(foo)
+#error "foo attribute supported"
+#endif
+
+#if 0
+#elif __has_c_attribute(foo)
+#error "foo attribute supported"
+#endif
diff --git a/gcc/testsuite/gcc.dg/c2x-has-c-attribute-2.c b/gcc/testsuite/gcc.dg/c2x-has-c-attribute-2.c
new file mode 100644
index 00000000000..d6c4c6de509
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-has-c-attribute-2.c
@@ -0,0 +1,41 @@
+/* Test __has_c_attribute.  Test supported attributes.  */
+/* { dg-do preprocess } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+#if __has_c_attribute ( nodiscard ) != 202003L
+#error "bad result for nodiscard"
+#endif
+
+#if __has_c_attribute ( __nodiscard__ ) != 202003L
+#error "bad result for __nodiscard__"
+#endif
+
+#if __has_c_attribute(maybe_unused) != 201904L
+#error "bad result for maybe_unused"
+#endif
+
+#if __has_c_attribute(__maybe_unused__) != 201904L
+#error "bad result for __maybe_unused__"
+#endif
+
+#if __has_c_attribute (deprecated) != 201904L
+#error "bad result for deprecated"
+#endif
+
+#if __has_c_attribute (__deprecated__) != 201904L
+#error "bad result for __deprecated__"
+#endif
+
+#if __has_c_attribute (fallthrough) != 201904L
+#error "bad result for fallthrough"
+#endif
+
+#if __has_c_attribute (__fallthrough__) != 201904L
+#error "bad result for __fallthrough__"
+#endif
+
+/* Macros in the attribute name are expanded.  */
+#define foo deprecated
+#if __has_c_attribute (foo) != 201904L
+#error "bad result for foo"
+#endif
diff --git a/gcc/testsuite/gcc.dg/c2x-has-c-attribute-3.c b/gcc/testsuite/gcc.dg/c2x-has-c-attribute-3.c
new file mode 100644
index 00000000000..36842ed41bc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-has-c-attribute-3.c
@@ -0,0 +1,25 @@
+/* Test __has_c_attribute.  Test GNU attributes.  */
+/* { dg-do preprocess } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+#if __has_c_attribute (gnu::packed) != 1
+#error "bad result for gnu::packed"
+#endif
+
+#if __has_c_attribute (__gnu__::__packed__) != 1
+#error "bad result for __gnu__::__packed__"
+#endif
+
+#if __has_c_attribute (gnu::__packed__) != 1
+#error "bad result for gnu::__packed__"
+#endif
+
+#if __has_c_attribute (__gnu__::packed) != 1
+#error "bad result for __gnu__::packed"
+#endif
+
+/* GNU attributes should not be reported as accepted without a scope
+   specified.  */
+#if __has_c_attribute (packed) != 0
+#error "bad result for packed"
+#endif
diff --git a/gcc/testsuite/gcc.dg/c2x-has-c-attribute-4.c b/gcc/testsuite/gcc.dg/c2x-has-c-attribute-4.c
new file mode 100644
index 00000000000..acd35d2d5ac
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-has-c-attribute-4.c
@@ -0,0 +1,18 @@
+/* Test __has_c_attribute.  Test syntax errors.  */
+/* { dg-do preprocess } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+#if __has_c_attribute /* { dg-error "missing '\\('" } */
+#endif
+
+#if __has_c_attribute 0 /* { dg-error "missing '\\('" } */
+#endif
+
+#if __has_c_attribute (0 /* { dg-error "requires an identifier" } */
+#endif
+
+#if __has_c_attribute (x /* { dg-error "missing '\\)'" } */
+#endif
+
+#if __has_c_attribute (x::0) /* { dg-error "required after scope" } */
+#endif
diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index c4d7cc520d1..8900e77c6e5 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -672,7 +672,7 @@ struct cpp_callbacks
   void (*used) (cpp_reader *, location_t, cpp_hashnode *);
 
   /* Callback to identify whether an attribute exists.  */
-  int (*has_attribute) (cpp_reader *);
+  int (*has_attribute) (cpp_reader *, bool);
 
   /* Callback to determine whether a built-in function is recognized.  */
   int (*has_builtin) (cpp_reader *);
@@ -857,6 +857,7 @@ enum cpp_builtin_type
   BT_TIMESTAMP,			/* `__TIMESTAMP__' */
   BT_COUNTER,			/* `__COUNTER__' */
   BT_HAS_ATTRIBUTE,		/* `__has_attribute(x)' */
+  BT_HAS_STD_ATTRIBUTE,		/* `__has_c_attribute(x)' */
   BT_HAS_BUILTIN,		/* `__has_builtin(x)' */
   BT_HAS_INCLUDE,		/* `__has_include(x)' */
   BT_HAS_INCLUDE_NEXT		/* `__has_include_next(x)' */
diff --git a/libcpp/init.c b/libcpp/init.c
index dcf1d4be587..1b43802c29c 100644
--- a/libcpp/init.c
+++ b/libcpp/init.c
@@ -407,6 +407,7 @@ static const struct builtin_macro builtin_array[] =
      function-like macros in traditional.c:
      fun_like_macro() when adding more following */
   B("__has_attribute",	 BT_HAS_ATTRIBUTE, true),
+  B("__has_c_attribute", BT_HAS_STD_ATTRIBUTE, true),
   B("__has_cpp_attribute", BT_HAS_ATTRIBUTE, true),
   B("__has_builtin",	 BT_HAS_BUILTIN,   true),
   B("__has_include",	 BT_HAS_INCLUDE,   true),
@@ -492,6 +493,7 @@ cpp_init_special_builtins (cpp_reader *pfile)
   for (b = builtin_array; b < builtin_array + n; b++)
     {
       if ((b->value == BT_HAS_ATTRIBUTE
+	   || b->value == BT_HAS_STD_ATTRIBUTE
 	   || b->value == BT_HAS_BUILTIN)
 	  && (CPP_OPTION (pfile, lang) == CLK_ASM
 	      || pfile->cb.has_attribute == NULL))
diff --git a/libcpp/macro.c b/libcpp/macro.c
index e2cb89e4c43..aa16752e2b2 100644
--- a/libcpp/macro.c
+++ b/libcpp/macro.c
@@ -648,7 +648,11 @@ _cpp_builtin_macro_text (cpp_reader *pfile, cpp_hashnode *node,
       break;
 
     case BT_HAS_ATTRIBUTE:
-      number = pfile->cb.has_attribute (pfile);
+      number = pfile->cb.has_attribute (pfile, false);
+      break;
+
+    case BT_HAS_STD_ATTRIBUTE:
+      number = pfile->cb.has_attribute (pfile, true);
       break;
 
     case BT_HAS_BUILTIN:
diff --git a/libcpp/traditional.c b/libcpp/traditional.c
index b087072c9b4..225e3c2c2f2 100644
--- a/libcpp/traditional.c
+++ b/libcpp/traditional.c
@@ -330,6 +330,7 @@ fun_like_macro (cpp_hashnode *node)
 {
   if (cpp_builtin_macro_p (node))
     return (node->value.builtin == BT_HAS_ATTRIBUTE
+	    || node->value.builtin == BT_HAS_STD_ATTRIBUTE
 	    || node->value.builtin == BT_HAS_BUILTIN
 	    || node->value.builtin == BT_HAS_INCLUDE
 	    || node->value.builtin == BT_HAS_INCLUDE_NEXT);