SIGABRT is in ANSI and POSIX.1, and SIGIOT isn't.

code/sys/sys_unix.c

@@ -813,7 +813,7 @@ void Sys_PlatformInit( void )
 	signal( SIGHUP, Sys_SigHandler );
 	signal( SIGQUIT, Sys_SigHandler );
 	signal( SIGTRAP, Sys_SigHandler );
-	signal( SIGIOT, Sys_SigHandler );
+	signal( SIGABRT, Sys_SigHandler );
 	signal( SIGBUS, Sys_SigHandler );
 
 	stdinIsATTY = isatty( STDIN_FILENO ) &&