Moved FfiClient instance to .cpp to ensure only one copy exists owned by the lib, added unit tests

Author: alan-george-lk

src/ffi_client.cpp

@@ -146,6 +146,11 @@ std::optional<FfiClient::AsyncId> ExtractAsyncId(const proto::FfiEvent& event) {
 
 } // namespace
 
+FfiClient& FfiClient::instance() noexcept {
+  static FfiClient instance;
+  return instance;
+}
+
 // clang-tidy flags this as a trivial destructor in release mode
 // due to the assert being pre-processed out
 // NOLINTNEXTLINE(modernize-use-equals-default)

src/ffi_client.h

@@ -74,10 +74,13 @@ class LIVEKIT_INTERNAL_API FfiClient {
   FfiClient(FfiClient&&) = delete;
   FfiClient& operator=(FfiClient&&) = delete;
 
-  static FfiClient& instance() noexcept {
-    static FfiClient instance;
-    return instance;
-  }
+  // Defined out-of-line in ffi_client.cpp so the process has exactly one
+  // FfiClient. An inline definition would, under the SDK's hidden inline
+  // visibility, produce a separate function-local static in every TU that
+  // includes this header (notably: in-tree test executables), giving each
+  // binary its own "singleton" and silently desynchronizing the dylib-side
+  // and test-exe-side initialization flags.
+  static FfiClient& instance() noexcept;
 
   // Must be called before any other FFI usage
   bool initialize(bool capture_logs);

src/livekit.cpp

@@ -22,19 +22,18 @@
 namespace livekit {
 
 bool initialize(const LogLevel& level, const LogSink& log_sink) {
+  // Initializes logger if singleton instance is not already initialized
   setLogLevel(level);
   auto& ffi_client = FfiClient::instance();
   return ffi_client.initialize(log_sink == LogSink::kCallback);
 }
 
 bool isInitialized() {
-  auto& ffi_client = FfiClient::instance();
-  return ffi_client.isInitialized();
+  return FfiClient::instance().isInitialized();
 }
 
 void shutdown() {
-  auto& ffi_client = FfiClient::instance();
-  ffi_client.shutdown();
+  FfiClient::instance().shutdown();
   detail::shutdownLogger();
 }