Dynamically load libpulse.so.0 and libasound.so.1 on Linux

By generating stubs using https://github.com/hpvb/dynload-wrapper we
can dynamically load libpulse and libasound on systems where it is available.
Both are still a build-time requirement but no longer a run-time dependency.

For maintenance purposes the wrappers should not need to be re-generated
unless we want to bump pulse or asound to an incompatible version. It is
unlikely we will want to do this any time soon.

This closes #20978

drivers/alsa/SCsub

@@ -2,4 +2,7 @@
 
 Import("env")
 
+if "alsa" in env and env["alsa"]:
+    env.add_source_files(env.drivers_sources, "asound-so_wrap.c")
+
 env.add_source_files(env.drivers_sources, "*.cpp")

drivers/alsa/audio_driver_alsa.cpp

@@ -37,6 +37,12 @@
 
 #include <errno.h>
 
+#ifdef PULSEAUDIO_ENABLED
+extern "C" {
+extern int initialize_pulse();
+}
+#endif
+
 Error AudioDriverALSA::init_device() {
 	mix_rate = GLOBAL_GET("audio/mix_rate");
 	speaker_mode = SPEAKER_MODE_STEREO;
@@ -147,6 +153,16 @@ Error AudioDriverALSA::init_device() {
 }
 
 Error AudioDriverALSA::init() {
+#ifdef PULSEAUDIO_ENABLED
+	// On pulse enabled systems Alsa will silently use pulse.
+	// It doesn't matter if this fails as that likely means there is no pulse
+	initialize_pulse();
+#endif
+
+	if (initialize_asound()) {
+		return ERR_CANT_OPEN;
+	}
+
 	active = false;
 	thread_exited = false;
 	exit_thread = false;

drivers/alsa/audio_driver_alsa.h

@@ -37,7 +37,7 @@
 #include "core/os/thread.h"
 #include "servers/audio_server.h"
 
-#include <alsa/asoundlib.h>
+#include "asound-so_wrap.h"
 
 class AudioDriverALSA : public AudioDriver {
 	Thread thread;

drivers/pulseaudio/SCsub

@@ -2,4 +2,7 @@
 
 Import("env")
 
+if "pulseaudio" in env and env["pulseaudio"]:
+    env.add_source_files(env.drivers_sources, "pulse-so_wrap.c")
+
 env.add_source_files(env.drivers_sources, "*.cpp")

drivers/pulseaudio/audio_driver_pulseaudio.cpp

@@ -233,6 +233,10 @@ Error AudioDriverPulseAudio::init_device() {
 }
 
 Error AudioDriverPulseAudio::init() {
+	if (initialize_pulse()) {
+		return ERR_CANT_OPEN;
+	}
+
 	active = false;
 	thread_exited = false;
 	exit_thread = false;

drivers/pulseaudio/audio_driver_pulseaudio.h

@@ -37,7 +37,7 @@
 #include "core/os/thread.h"
 #include "servers/audio_server.h"
 
-#include <pulse/pulseaudio.h>
+#include "pulse-so_wrap.h"
 
 class AudioDriverPulseAudio : public AudioDriver {
 	Thread thread;

misc/scripts/clang_format.sh

@@ -16,6 +16,8 @@ while IFS= read -rd '' f; do
         continue
     elif [[ "$f" == "platform/android/java/lib/src/com/google"* ]]; then
         continue
+    elif [[ "$f" == *"-so_wrap."* ]]; then
+        continue
     fi
 
     for extension in ${CLANG_FORMAT_FILE_EXTS[@]}; do

platform/linuxbsd/detect.py

@@ -310,9 +310,8 @@ def configure(env):
 
     if os.system("pkg-config --exists alsa") == 0:  # 0 means found
         print("Enabling ALSA")
+        env["alsa"] = True
         env.Append(CPPDEFINES=["ALSA_ENABLED", "ALSAMIDI_ENABLED"])
-        # Don't parse --cflags, we don't need to add /usr/include/alsa to include path
-        env.ParseConfig("pkg-config alsa --libs")
     else:
         print("ALSA libraries not found, disabling driver")
 
@@ -320,7 +319,7 @@ def configure(env):
         if os.system("pkg-config --exists libpulse") == 0:  # 0 means found
             print("Enabling PulseAudio")
             env.Append(CPPDEFINES=["PULSEAUDIO_ENABLED"])
-            env.ParseConfig("pkg-config --cflags --libs libpulse")
+            env.ParseConfig("pkg-config --cflags libpulse")
         else:
             print("PulseAudio development libraries not found, disabling driver")