add C++ guards

include/ucore/read_file.h

@@ -3,6 +3,10 @@
 
 #include <stddef.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /** Read the content of a file.
  * The returned char* is malloced memory and must be freed by the caller.
  * The content is terminated by a nul byte, regardless of whether the content 
@@ -17,4 +21,8 @@
 char *
 uc_read_file(const char *file_name, size_t *length, size_t max);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif