Pass the Apple event tracer's C++ handle opaquely across the framework boundary

extension/apple/BUCK

@@ -8,11 +8,6 @@ oncall("executorch")
 
 non_fbcode_target(_kind = fb_apple_library,
     name = "ExecuTorch",
-    # The ETDump extension subclasses ExecuTorchEventTracer, which needs the C++
-    # tracer seam this header declares, so export it beyond the target.
-    autoglob_additional_exported_headers = [
-        "ExecuTorch/Internal/ExecuTorchEventTracer+Internal.h",
-    ],
     autoglob_mode = "EXPORT_UNLESS_INTERNAL",
     extension_api_only = True,
     frameworks = [

extension/apple/ExecuTorch/Exported/ExecuTorchEventTracer.h

@@ -30,6 +30,24 @@ NS_SWIFT_NAME(EventTracer)
 + (instancetype)new NS_UNAVAILABLE;
 - (instancetype)init NS_UNAVAILABLE;
 
+/**
+ * Initializes a tracer with a native std::unique_ptr<EventTracer> instance.
+ *
+ * @param nativeInstance A pointer to a native std::unique_ptr<EventTracer>
+ * instance.
+ * @return An initialized ExecuTorchEventTracer instance.
+ */
+- (instancetype)initWithNativeInstance:(void *)nativeInstance
+    NS_DESIGNATED_INITIALIZER NS_SWIFT_UNAVAILABLE("");
+
+/**
+ * Pointer to the underlying native std::unique_ptr<EventTracer> instance.
+ *
+ * @return A raw pointer to the native std::unique_ptr<EventTracer> held by this
+ * class.
+ */
+@property(nonatomic, readonly) void *nativeInstance NS_SWIFT_UNAVAILABLE("");
+
 @end
 
 NS_ASSUME_NONNULL_END

extension/apple/ExecuTorch/Exported/ExecuTorchEventTracer.mm

@@ -8,24 +8,26 @@
 
 #import "ExecuTorchEventTracer.h"
 
-#import "ExecuTorchEventTracer+Internal.h"
+#import <executorch/runtime/core/event_tracer.h>
 
 using executorch::runtime::EventTracer;
 
 @implementation ExecuTorchEventTracer {
   std::unique_ptr<EventTracer> _tracer;
 }
 
-- (instancetype)initWithCppTracer:(std::unique_ptr<EventTracer>)tracer {
-  self = [super init];
-  if (self) {
-    _tracer = std::move(tracer);
+- (instancetype)initWithNativeInstance:(void *)nativeInstance {
+  ET_CHECK(nativeInstance);
+  if (self = [super init]) {
+    _tracer = std::move(
+        *reinterpret_cast<std::unique_ptr<EventTracer> *>(nativeInstance));
+    ET_CHECK(_tracer);
   }
   return self;
 }
 
-- (std::unique_ptr<EventTracer>)takeCppTracer {
-  return std::move(_tracer);
+- (void *)nativeInstance {
+  return &_tracer;
 }
 
 @end

extension/apple/ExecuTorch/Exported/ExecuTorchModule.mm

@@ -12,7 +12,6 @@
 #import "ExecuTorchBackendOptionsMap+Internal.h"
 #import "ExecuTorchBackendOptionsMap.h"
 #import "ExecuTorchError.h"
-#import "ExecuTorchEventTracer+Internal.h"
 #import "ExecuTorchUtils.h"
 
 #import <executorch/extension/module/module.h>
@@ -330,7 +329,10 @@ - (instancetype)initWithFilePath:(NSString *)filePath
     // Taking it empties the handle, so a tracer handed to a second module would
     // yield nothing and that module would run and record silently into nowhere.
     // Catch it here rather than letting it surface as an empty profile.
-    auto cppTracer = [eventTracer takeCppTracer];
+    auto *cppTracerPtr = reinterpret_cast<std::unique_ptr<EventTracer> *>(
+        eventTracer.nativeInstance);
+    ET_CHECK(cppTracerPtr);
+    auto cppTracer = std::move(*cppTracerPtr);
     NSAssert(cppTracer != nullptr,
              @"This event tracer was already given to another module. Create one "
              @"tracer per module.");

extension/apple/dump/CMakeLists.txt

@@ -25,15 +25,13 @@ target_sources(extension_etdump_apple PRIVATE ${OBJC_SOURCES})
 # The public header exposes ExecuTorchModule and so imports it as
 # <ExecuTorch/ExecuTorchModule.h>, the path a consumer of the assembled
 # framework uses. That layout does not exist during this build, so stage the
-# core Exported and Internal headers under one ExecuTorch directory and put it
-# on the include path, mirroring what the framework packaging produces. Staging
-# them together in one directory is what lets the Internal header's own quoted
-# import of "ExecuTorchModule.h" find its sibling, and keeps the module header
-# reachable by a single path so it is not seen as two conflicting definitions.
+# core Exported headers under one ExecuTorch directory and put it on the include
+# path, mirroring what the framework packaging produces. Staging them together
+# in one directory keeps the module header reachable by a single path so it is
+# not seen as two conflicting definitions.
 set(_etdump_core_headers_dir ${CMAKE_CURRENT_BINARY_DIR}/include)
 file(GLOB _etdump_core_headers
      ${EXECUTORCH_ROOT}/extension/apple/ExecuTorch/Exported/*.h
-     ${EXECUTORCH_ROOT}/extension/apple/ExecuTorch/Internal/*.h
 )
 # configure_file(... COPYONLY) rather than file(COPY): it registers each source
 # header as a reconfigure dependency, so editing a core header re-stages it. A

extension/apple/dump/ExecuTorchDump/Exported/ExecuTorchDumpTracer.mm

@@ -11,8 +11,6 @@
 #import "ExecuTorchDumpError.h"
 #import "ExecuTorchDumpTracer+Internal.h"
 
-#import <ExecuTorch/ExecuTorchEventTracer+Internal.h>
-
 #import <flatcc/flatcc_builder.h>
 
 using namespace executorch::etdump;
@@ -39,25 +37,21 @@ @implementation ExecuTorchDumpTracer {
   NSLock *_lock;
 }
 
-// init chains to the base class's real designated initializer, initWithCppTracer:,
-// which takes a C++ type and so lives in an Objective-C++ category rather than the
-// public interface. Clang cannot see a category initializer as designated, so it
-// wrongly flags this chain; the pattern is deliberate and correct.
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wobjc-designated-initializers"
-
 - (instancetype)init {
   auto generator = std::make_unique<ETDumpGen>();
   _generator = generator.get();
-  self = [super initWithCppTracer:std::move(generator)];
+  // The base moves out of the pointee as a std::unique_ptr<EventTracer>, so the
+  // local must be that type, not unique_ptr<ETDumpGen>. _generator keeps the
+  // concrete pointer for readback.
+  std::unique_ptr<executorch::runtime::EventTracer> tracer =
+      std::move(generator);
+  self = [super initWithNativeInstance:&tracer];
   if (self) {
     _lock = [NSLock new];
   }
   return self;
 }
 
-#pragma clang diagnostic pop
-
 - (ETDumpGen *)generator {
   return _generator;
 }