The g++ iostream.h headers explicitly do using std::cout etc clang just has the standard headers.
Index: patches/patch-sid2wav_cpp =================================================================== RCS file: patches/patch-sid2wav_cpp diff -N patches/patch-sid2wav_cpp --- /dev/null 1 Jan 1970 00:00:00 -0000 +++ patches/patch-sid2wav_cpp 20 Apr 2017 07:00:45 -0000 @@ -0,0 +1,25 @@ +$OpenBSD$ +--- sid2wav.cpp.orig Thu Apr 20 16:59:16 2017 ++++ sid2wav.cpp Thu Apr 20 16:59:52 2017 +@@ -18,9 +18,9 @@ + // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + // + +-#include <iostream.h> +-#include <iomanip.h> +-#include <fstream.h> ++#include <iostream> ++#include <iomanip> ++#include <fstream> + #include <string.h> + + #include <stdlib.h> +@@ -38,6 +38,8 @@ + #include <sidplay/player.h> + #include <sidplay/fformat.h> + #include <sidplay/myendian.h> ++ ++using namespace std; + + const char s2w_version[] = "1.8"; + Index: patches/patch-sidcon_cpp =================================================================== RCS file: patches/patch-sidcon_cpp diff -N patches/patch-sidcon_cpp --- /dev/null 1 Jan 1970 00:00:00 -0000 +++ patches/patch-sidcon_cpp 20 Apr 2017 07:00:53 -0000 @@ -0,0 +1,19 @@ +$OpenBSD$ +--- sidcon.cpp.orig Thu Apr 20 17:00:09 2017 ++++ sidcon.cpp Thu Apr 20 17:00:34 2017 +@@ -25,11 +25,13 @@ + #include <stdio.h> + #include <stdlib.h> + #include <string.h> +-#include <iostream.h> +-#include <iomanip.h> ++#include <iostream> ++#include <iomanip> + + #include <sidplay/sidtune.h> + #include <sidplay/fformat.h> ++ ++using namespace std; + + static bool toPSID = true, + toSIDPLAY = false, Index: patches/patch-sidplay_cpp =================================================================== RCS file: patches/patch-sidplay_cpp diff -N patches/patch-sidplay_cpp --- /dev/null 1 Jan 1970 00:00:00 -0000 +++ patches/patch-sidplay_cpp 20 Apr 2017 07:00:45 -0000 @@ -0,0 +1,24 @@ +$OpenBSD$ +--- sidplay.cpp.orig Thu Apr 20 16:54:28 2017 ++++ sidplay.cpp Thu Apr 20 16:58:52 2017 +@@ -18,8 +18,9 @@ + // + + #include <ctype.h> +-#include <iomanip.h> +-#include <fstream.h> ++#include <iomanip> ++#include <fstream> ++#include <iostream> + #include <signal.h> + #include <stdlib.h> + #include <string.h> +@@ -29,6 +30,8 @@ + #include <sidplay/fformat.h> + #include <sidplay/myendian.h> + #include "audiodrv.h" ++ ++using namespace std; + + #if defined(__amigaos__) + #define EXIT_ERROR_STATUS (20)
