/* returns a pointer to the FILE, and puts the size in bytes into mbox_file_size
* normally, source_file_override is NULL */
-FILE *spool_mbox(unsigned long *mbox_file_size, uschar *source_file_override) {
+FILE *
+spool_mbox(unsigned long *mbox_file_size, const uschar *source_file_override)
+{
uschar message_subdir[2];
uschar buffer[16384];
uschar *temp_string;