Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -187,10 +187,15 @@
 	TESTS_OBJCFLAGS="$TESTS_OBJCFLAGS -Wno-atomic-properties"
 ])
 
 AC_MSG_CHECKING(whether Objective C compiler supports properties)
 AC_TRY_COMPILE([
+	#ifdef __has_attribute
+	# if __has_attribute(objc_root_class)
+	__attribute__((__objc_root_class__))
+	# endif
+	#endif
 	@interface Foo
 	{
 		id bar;
 	}
 
@@ -296,10 +301,15 @@
 		AC_MSG_CHECKING([whether -fobjc-runtime=objfw is supported])
 
 		old_OBJCFLAGS="$OBJCFLAGS"
 		OBJCFLAGS="$OBJCFLAGS -fobjc-runtime=objfw"
 		AC_TRY_LINK([
+			#ifdef __has_attribute
+			# if __has_attribute(objc_root_class)
+			__attribute__((__objc_root_class__))
+			# endif
+			#endif
 			@interface Test
 			+ (void)test;
 			@end
 
 			@implementation Test
@@ -1265,10 +1275,15 @@
 AS_IF([test x"$GOBJC" = x"yes"], [
 	OBJCFLAGS="$OBJCFLAGS -Wwrite-strings -Wpointer-arith -Werror"
 
 	AC_MSG_CHECKING(whether we need -Wno-strict-aliasing due to GCC bugs)
 	AC_TRY_COMPILE([
+		#ifdef __has_attribute
+		# if __has_attribute(objc_root_class)
+		__attribute__((__objc_root_class__))
+		# endif
+		#endif
 		@interface Foo
 		{
 			struct objc_class *_isa;
 		}
 		@end
@@ -1427,10 +1442,15 @@
 	AC_MSG_CHECKING(whether -Wdocumentation works correctly)
 	AC_TRY_COMPILE([
 		/*!
 		 * @class Test conftest.m conftest.m
 		 */
+		#ifdef __has_attribute
+		# if __has_attribute(objc_root_class)
+		__attribute__((__objc_root_class__))
+		# endif
+		#endif
 		@interface Test
 		@end
 	], [
 	], [
 		AC_MSG_RESULT(yes)
@@ -1446,10 +1466,15 @@
 		AC_TRY_COMPILE([
 			#include <stdlib.h>
 
 			#include <assert.h>
 
+			#ifdef __has_attribute
+			# if __has_attribute(objc_root_class)
+			__attribute__((__objc_root_class__))
+			# endif
+			#endif
 			@interface Foo
 			{
 				void *foo;
 			}
 			@end