--- rtaudio-4.0.12/configure.ac
+++ rtaudio-4.0.12/configure.ac
@@ -25,9 +25,9 @@
 AC_PROG_CXX(g++ CC c++ cxx)
 AC_PROG_RANLIB
 AC_PATH_PROG(AR, ar, no)
-if [[ $AR = "no" ]] ; then
-    AC_MSG_ERROR("Could not find ar - needed to create a library");
-fi
+AS_IF([test "x$AR" == "x" ], [
+  AC_MSG_ERROR("Could not find ar - needed to create a library")
+])
 
 # Checks for header files.
 AC_HEADER_STDC
@@ -83,39 +83,46 @@
   ;;
 
   *-*-linux*)
-  AC_ARG_WITH(jack, [  --with-jack = choose JACK server support (mac and linux only)], [
+  AC_ARG_WITH([jack], AS_HELP_STRING([--with-jack], [choose JACK server support (mac and linux only)]))
+
+  AS_IF([test "x$with_jack" != "xno"], [
     api="$api -D__UNIX_JACK__"
     AC_MSG_RESULT(using JACK)
     AC_CHECK_LIB(jack, jack_client_open, , AC_MSG_ERROR(JACK support requires the jack library!))
-    AC_CHECK_LIB(asound, snd_pcm_open, , AC_MSG_ERROR(Jack support also requires the asound library!))], )
+    AC_CHECK_LIB(asound, snd_pcm_open, , AC_MSG_ERROR(Jack support also requires the asound library!))])
 
   # Look for ALSA flag
-  AC_ARG_WITH(alsa, [  --with-alsa = choose native ALSA API support (linux only)], [
+  AC_ARG_WITH([alsa], AS_HELP_STRING([--with-alsa], [choose native ALSA API support (linux only)]))
+
+  AS_IF([test "x$with_alsa" != "xno"], [
     api="$api -D__LINUX_ALSA__"
     req="$req alsa"
     AC_MSG_RESULT(using ALSA)
-    AC_CHECK_LIB(asound, snd_pcm_open, , AC_MSG_ERROR(ALSA support requires the asound library!))], )
+    AC_CHECK_LIB(asound, snd_pcm_open, , AC_MSG_ERROR(ALSA support requires the asound library!))])
 
   # Look for PULSE flag
-  AC_ARG_WITH(pulse, [  --with-pulse = choose PulseAudio API support (linux only)], [
+  AC_ARG_WITH([pulse], AS_HELP_STRING([--with-pulse], [choose PulseAudio API support (linux only)]))
+
+  AS_IF([test "x$with_pulse" != "xno"], [
     api="$api -D__LINUX_PULSE__"
     req="$req libpulse-simple"
     AC_MSG_RESULT(using PulseAudio)
     PKG_CHECK_MODULES([PULSE], [libpulse-simple], , AC_MSG_ERROR(PulseAudio support requires the pulse-simple library!))
-        LIBS="$LIBS `pkg-config --libs libpulse-simple`" ], )
+        LIBS="$LIBS `pkg-config --libs libpulse-simple`" ])
 
   # Look for OSS flag
-  AC_ARG_WITH(oss, [  --with-oss = choose OSS API support (linux only)], [
+  AC_ARG_WITH([oss], AS_HELP_STRING([--with-oss], [choose OSS API support (linux only)]))
+
+  AS_IF([test "x$with_oss" != "xno"], [
     api="$api -D__LINUX_OSS__"
-    AC_MSG_RESULT(using OSS)], )
+    AC_MSG_RESULT(using OSS)])
 
   # If no audio api flags specified, use ALSA
-  if [test "$api" == "";] then
+  AS_IF([test "x$api" == "x"], [
     AC_MSG_RESULT(using ALSA)
     AC_SUBST( api, [-D__LINUX_ALSA__] )
     req="$req alsa"
-    AC_CHECK_LIB(asound, snd_pcm_open, , AC_MSG_ERROR(ALSA support requires the asound library!))
-  fi
+    AC_CHECK_LIB(asound, snd_pcm_open, , AC_MSG_ERROR(ALSA support requires the asound library!))])
 
   AC_CHECK_LIB(pthread, pthread_create, , AC_MSG_ERROR(RtAudio requires the pthread library!))
   ;;