SDLInputSource: Centralize SDL subsystem loading

src/util/dyn_libs.cpp

@@ -17,6 +17,7 @@
 #include "common/error.h"
 #include "common/log.h"
 
+#include <atomic>
 #include <utility>
 
 LOG_CHANNEL(DynamicLibrary);
@@ -59,6 +60,8 @@ static constexpr int SPIRV_CROSS_MAJOR_VERSION = SPVC_C_API_VERSION_MAJOR;
 namespace {
 struct Locals
 {
+  ~Locals();
+
   DynamicLibrary freetype_library;
   std::once_flag freetype_init_flag;
   DynamicLibrary plutosvg_library;
@@ -73,6 +76,7 @@ struct Locals
   std::once_flag libzip_init_flag;
   DynamicLibrary sdl_library;
   std::once_flag sdl_init_flag;
+  std::atomic<SDL_InitFlags> sdl_init_subsystems{0};
   DynamicLibrary sqlite_library;
   std::once_flag sqlite_init_flag;
   DynamicLibrary shaderc_library;
@@ -80,10 +84,6 @@ struct Locals
   shaderc_compiler_t shaderc_compiler;
   DynamicLibrary spirv_cross_library;
   std::once_flag spirv_cross_init_flag;
-
-#if defined(_DEBUG) || defined(_DEVEL)
-  ~Locals();
-#endif
 };
 } // namespace
 
@@ -99,14 +99,14 @@ DynShaderc g_dyn_shaderc;
 DynSpirvCross g_dyn_spirv_cross;
 static Locals s_locals;
 
-#if defined(_DEBUG) || defined(_DEVEL)
-
 Locals::~Locals()
 {
   DebugAssert(!s_locals.shaderc_compiler);
-}
 
-#endif
+  // Quit any persistent SDL subsystems before unloading the library.
+  if (const SDL_InitFlags active_subsystems = s_locals.sdl_init_subsystems.load(std::memory_order_acquire))
+    g_dyn_sdl.SDL_QuitSubSystem(active_subsystems);
+}
 
 static bool LoadDynLib(const char* libname, int major_version, DynamicLibrary& dynlib, std::once_flag& once_flag,
                        std::span<const DynamicLibrary::SymbolTable> symbols, Error* const error,
@@ -273,7 +273,7 @@ static bool SDLLoadCallback(Error* const error)
   return true;
 }
 
-bool DynSDL::Open(Error* error)
+bool DynSDL::Open(Error* const error)
 {
   if (s_locals.sdl_library.IsOpen()) [[likely]]
     return true;
@@ -282,6 +282,31 @@ bool DynSDL::Open(Error* error)
                     SDLLoadCallback);
 }
 
+bool DynSDL::InitSubSystem(SDL_InitFlags flags, Error* const error)
+{
+  // anything added?
+  const SDL_InitFlags prev_subsystems = s_locals.sdl_init_subsystems.fetch_or(flags, std::memory_order_acq_rel);
+  const SDL_InitFlags subsystems_to_init = (flags & ~prev_subsystems);
+  if (subsystems_to_init == 0 || SDL_InitSubSystem(subsystems_to_init))
+    return true;
+
+  s_locals.sdl_init_subsystems.fetch_and(~subsystems_to_init, std::memory_order_acq_rel);
+
+  const char* sdl_error = SDL_GetError();
+  Error::SetStringFmt(error, "SDL_InitSubSystem(0x{:08X}) failed: {}", static_cast<u32>(subsystems_to_init),
+                      sdl_error ? sdl_error : "");
+  return false;
+}
+
+void DynSDL::QuitSubSystem(SDL_InitFlags flags)
+{
+  // anything removed?
+  const SDL_InitFlags prev_subsystems = s_locals.sdl_init_subsystems.fetch_and(~flags, std::memory_order_acq_rel);
+  const SDL_InitFlags subsystems_to_release = (flags & prev_subsystems);
+  if (subsystems_to_release != 0)
+    SDL_QuitSubSystem(subsystems_to_release);
+}
+
 static const DynamicLibrary::SymbolTable s_shaderc_symbols[] = {
 #define RESOLVE_SYMBOL(F) {#F, (void**)&g_dyn_shaderc.F},
   DYN_SHADERC_FUNCTIONS(RESOLVE_SYMBOL)

src/util/dyn_sdl.h

@@ -75,7 +75,9 @@ struct DynSDL
   DYN_SDL_FUNCTIONS(ADD_FUNC)
 #undef ADD_FUNC
 
-  bool Open(Error* error);
+  bool Open(Error* const error);
+  bool InitSubSystem(SDL_InitFlags flags, Error* const error);
+  void QuitSubSystem(SDL_InitFlags flags);
 };
 
 extern DynSDL g_dyn_sdl;

src/util/sdl_audio_stream.cpp

@@ -33,28 +33,6 @@ protected:
 };
 } // namespace
 
-static bool InitializeSDLAudio(Error* error)
-{
-  static bool initialized = false;
-  if (initialized)
-    return true;
-
-  if (!g_dyn_sdl.Open(error))
-    return false;
-
-  // May as well keep it alive until the process exits.
-  if (!g_dyn_sdl.SDL_InitSubSystem(SDL_INIT_AUDIO))
-  {
-    Error::SetStringFmt(error, "SDL_InitSubSystem(SDL_INIT_AUDIO) failed: {}", g_dyn_sdl.SDL_GetError());
-    return false;
-  }
-
-  std::atexit([]() { g_dyn_sdl.SDL_QuitSubSystem(SDL_INIT_AUDIO); });
-
-  initialized = true;
-  return true;
-}
-
 SDLAudioStream::SDLAudioStream(AudioStreamSource* source, u32 channels) : m_source(source), m_channels(channels)
 {
 }
@@ -129,7 +107,8 @@ std::unique_ptr<AudioStream> AudioStream::CreateSDLAudioStream(u32 sample_rate,
                                                                bool output_latency_minimal, AudioStreamSource* source,
                                                                bool auto_start, Error* error)
 {
-  if (!InitializeSDLAudio(error))
+  // May as well keep it alive until the process exits.
+  if (!g_dyn_sdl.Open(error) || !g_dyn_sdl.InitSubSystem(SDL_INIT_AUDIO, error))
     return {};
 
   std::unique_ptr<SDLAudioStream> stream = std::make_unique<SDLAudioStream>(source, channels);

src/util/sdl_input_source.cpp

@@ -582,15 +582,13 @@ void SDLInputSource::SetHints()
 
 bool SDLInputSource::InitializeSubsystem()
 {
-  if (!g_dyn_sdl.SDL_InitSubSystem(SDL_INIT_JOYSTICK | SDL_INIT_GAMEPAD | SDL_INIT_HAPTIC))
+  if (Error error; !g_dyn_sdl.InitSubSystem(SDL_INIT_JOYSTICK | SDL_INIT_GAMEPAD | SDL_INIT_HAPTIC, &error))
   {
-    ERROR_LOG("SDL_InitSubSystem(SDL_INIT_JOYSTICK | SDL_INIT_GAMEPAD | SDL_INIT_HAPTIC) failed");
+    ERROR_LOG(error.GetDescription());
     return false;
   }
 
   // we should open the controllers as the connected events come in, so no need to do any more here
-  m_sdl_subsystem_initialized = true;
-
   int mapping_count = 0;
   g_dyn_sdl.SDL_free(g_dyn_sdl.SDL_GetGamepadMappings(&mapping_count));
   INFO_LOG("{} controller mappings are loaded.", mapping_count);
@@ -603,11 +601,7 @@ void SDLInputSource::ShutdownSubsystem()
   while (!m_controllers.empty())
     CloseDevice(m_controllers.begin()->joystick_id);
 
-  if (m_sdl_subsystem_initialized)
-  {
-    g_dyn_sdl.SDL_QuitSubSystem(SDL_INIT_JOYSTICK | SDL_INIT_GAMEPAD | SDL_INIT_HAPTIC);
-    m_sdl_subsystem_initialized = false;
-  }
+  g_dyn_sdl.QuitSubSystem(SDL_INIT_JOYSTICK | SDL_INIT_GAMEPAD | SDL_INIT_HAPTIC);
 }
 
 void SDLInputSource::PollEvents()