There is currently no reason to have a different <cryb/impl.h>.

bin/otpkey/otpkey.c

@@ -27,7 +27,7 @@
  * SUCH DAMAGE.
  */
 
-#include "cryb/otp-impl.h"
+#include "cryb/impl.h"
 
 #include <stdio.h>
 #include <stdlib.h>

include/cryb/Makefile.am

@@ -7,4 +7,4 @@ cryb_HEADERS += otp.h
 endif OTP_LIB
 
 noinst_HEADERS = \
-	otp-impl.h
+	impl.h

include/cryb/impl.h

@@ -1,5 +1,5 @@
 /*-
- * Copyright (c) 2017 Dag-Erling Smørgrav
+ * Copyright (c) 2014-2016 Dag-Erling Smørgrav
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -27,8 +27,8 @@
  * SUCH DAMAGE.
  */
 
-#ifndef CRYB_OTP_IMPL_H_INCLUDED
-#define CRYB_OTP_IMPL_H_INCLUDED
+#ifndef CRYB_IMPL_H_INCLUDED
+#define CRYB_IMPL_H_INCLUDED
 
 #if HAVE_CONFIG_H
 #include "config.h"

lib/otp/cryb_otp.c

@@ -27,7 +27,7 @@
  * SUCH DAMAGE.
  */
 
-#include "cryb/otp-impl.h"
+#include "cryb/impl.h"
 
 #include <stdint.h>
 #include <unistd.h>

libexec/login_otp/login_otp.c

@@ -27,7 +27,7 @@
  * SUCH DAMAGE.
  */
 
-#include "cryb/otp-impl.h"
+#include "cryb/impl.h"
 
 #include <stdio.h>
 #include <stdlib.h>

pam/pam_otp/pam_otp.c

@@ -27,7 +27,7 @@
  * SUCH DAMAGE.
  */
 
-#include "cryb/otp-impl.h"
+#include "cryb/impl.h"
 
 #define PAM_SM_AUTH
 

sbin/otpradiusd/otpradiusd.c

@@ -27,7 +27,7 @@
  * SUCH DAMAGE.
  */
 
-#include "cryb/otp-impl.h"
+#include "cryb/impl.h"
 
 #include <stdio.h>
 #include <stdlib.h>

t/t_cxx.cc

@@ -27,7 +27,7 @@
  * SUCH DAMAGE.
  */
 
-#include "cryb/otp-impl.h"
+#include "cryb/impl.h"
 
 /* gcc's <cstdint> is broken */
 #include <stdint.h>