--- a/src/extern.h
+++ b/src/extern.h
@@ -97,7 +97,8 @@ extern char input_is_special;
 extern char output_is_special;
 extern char input_is_seekable;
 extern char output_is_seekable;
-extern int (*xstat) ();
+//void not good enough
+extern int (*xstat) (const char * restrict,  struct stat * restrict);
 extern void (*copy_function) ();
 extern char *change_directory_option;
 
--- a/src/global.c
+++ b/src/global.c
@@ -185,7 +185,7 @@ bool to_stdout_option = false;
 
 /* A pointer to either lstat or stat, depending on whether
    dereferencing of symlinks is done for input files.  */
-int (*xstat) ();
+int (*xstat) (const char * restrict,  struct stat * restrict);
 
 /* Which copy operation to perform. (-i, -o, -p) */
 void (*copy_function) () = 0;