Michael Curtis adjusted this for RISC OS

src/setup.h

@@ -46,6 +46,9 @@
 /* this is not the same as Mac OS X */
 #include "config-mac.h"
 #endif
+#ifdef __riscos__
+#include "config-riscos.h"
+#endif
 #endif
 
 #ifndef OS
@@ -77,4 +80,8 @@ int fileno( FILE *stream);
 #endif
 #endif
 
+#ifdef __riscos__
+#define USE_ENVIRONMENT
+#endif
+
 #endif /* __SETUP_H */