Date: Sun, 29 Feb 2004 15:14:22 +0200

From: Martin_Storsj
Subject: Dynamic loading of ALSA

I recently discovered that SDL can dynamically load ESD and aRts, and
made a patch which adds this same functionality to ALSA.

The update for configure.in isn't too good (it should e.g. look for
libasound.so in other directories than /usr/lib), because I'm not too
good at shellscripting and autoconf.

The reason for using dlfcn.h and dlopen instead of SDL_LoadLibrary and
SDL_LoadFunction is that libasound uses versioned symbols, and it is
necessary to load the correct version using dlvsym. This isn't probably
any real portability issue, because ALSA is linux-only.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%40866

configure.in

@@ -295,8 +295,22 @@ CheckALSA()
         AC_CHECK_LIB(asound, snd_pcm_open, have_alsa=yes)
         ])
         if test x$have_alsa = xyes; then
-            CFLAGS="$CFLAGS -DALSA_SUPPORT"
-            SYSTEM_LIBS="$SYSTEM_LIBS -lasound"
+            AC_ARG_ENABLE(alsa-shared,
+[  --enable-alsa-shared     dynamically load ALSA audio support [default=yes]],
+                          , enable_alsa_shared=yes)
+            alsa_lib=`ls /usr/lib/libasound.so.* | head -1 | sed 's/.*\/\(.*\)/\1/'`
+            if test x$use_dlopen != xyes && \
+               test x$enable_alsa_shared = xyes; then
+                AC_MSG_ERROR([You must have dlopen() support and use the --enable-dlopen option])
+            fi
+            if test x$use_dlopen = xyes && \
+               test x$enable_alsa_shared = xyes && test x$alsa_lib != x; then
+                CFLAGS="$CFLAGS -DALSA_SUPPORT -DALSA_DYNAMIC=\$(alsa_lib)"
+                AC_SUBST(alsa_lib)
+            else
+                CFLAGS="$CFLAGS -DALSA_SUPPORT"
+                SYSTEM_LIBS="$SYSTEM_LIBS -lasound"
+            fi
             AUDIO_SUBDIRS="$AUDIO_SUBDIRS alsa"
             AUDIO_DRIVERS="$AUDIO_DRIVERS alsa/libaudio_alsa.la"
         else

src/audio/alsa/Makefile.am

@@ -4,6 +4,8 @@
 noinst_LTLIBRARIES = libaudio_alsa.la
 libaudio_alsa_la_SOURCES = $(SRCS)
 
+alsa_lib = \"@alsa_lib@\"
+
 # The SDL audio driver sources
 SRCS =	SDL_alsa_audio.c	\
 	SDL_alsa_audio.h