os: create generic_base.h for _DECLS macros

Author: MaxDesiatov

os/CMakeLists.txt

@@ -3,9 +3,10 @@
 # voucher_private.h are included in the source tarball
 
 install(FILES
-          object.h
+          generic_base.h
           generic_unix_base.h
           generic_win_base.h
+          object.h
         DESTINATION
           "${INSTALL_OS_HEADERS_DIR}")
 

os/generic_base.h

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2011-2014 Apple Inc. All rights reserved.
+ *
+ * @APPLE_APACHE_LICENSE_HEADER_START@
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * @APPLE_APACHE_LICENSE_HEADER_END@
+ */
+
+#ifndef __OS_GENERIC_BASE__
+#define __OS_GENERIC_BASE__
+
+#if !defined(__BEGIN_DECLS) && !defined(__END_DECLS)
+#if defined(__cplusplus)
+#define __BEGIN_DECLS extern "C" {
+#define __END_DECLS }
+#else
+#define __BEGIN_DECLS
+#define __END_DECLS
+#endif
+#endif
+
+#endif /* __OS_GENERIC_BASE__ */

os/generic_unix_base.h

@@ -13,6 +13,8 @@
 #ifndef __OS_GENERIC_UNIX_BASE__
 #define __OS_GENERIC_UNIX_BASE__
 
+#include <os/generic_base.h>
+
 #if __has_include(<sys/sysmacros.h>)
 #include <sys/sysmacros.h>
 #endif

os/generic_win_base.h

@@ -13,6 +13,8 @@
 #ifndef __OS_GENERIC_WIN_BASE__
 #define __OS_GENERIC_WIN_BASE__
 
+#include <os/generic_base.h>
+
 // Unices provide `roundup` via sys/param.h
 #define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y))
 // Unices provide `MAX` via sys/param.h