Android: build/runtime fixes for modern Clang + ETDump path override

Three small fixes needed to build and run ExecuTorch Android on hosts with
Apple Clang 21 and on devices where /data/local/tmp isn't app-writable:

1. Workaround flatcc's vendored CMakeLists.txt hitting -Werror on new Clang
   warnings (-Wimplicit-int-conversion-on-negation,
   -Wunterminated-string-initialization). Passes FLATCC_ALLOW_WERROR=OFF
   into both the top-level flatcc CMake build and the flatcc_ep
   ExternalProject.

2. scripts/build_android_library.sh was setting EXECUTORCH_ENABLE_EVENT_TRACER
   from $EXECUTORCH_ANDROID_PROFILING but never forwarding the separate
   -DEXECUTORCH_ANDROID_PROFILING define that gates ETDumpGen allocation in
   extension/android/jni/jni_layer.cpp. As a result, the event tracer was
   compiled in but the JNI never attached it, and Module.etdump() always
   returned false.

3. Add Module.etdump(String outputPath) / etdumpTo() JNI method so apps can
   write the ETDump into their own filesDir. The existing etdump()
   hardcodes /data/local/tmp/result.etdump, which is not app-writable on
   modern Android (Pixel 9 / API 36 returns EACCES). The new overload
   factors the write path through a shared etdump_to_path() helper;
   etdump() now delegates to it with the legacy path.

Author: jgibson2

extension/android/executorch_android/src/main/java/org/pytorch/executorch/Module.java

@@ -265,6 +265,28 @@ public boolean etdump() {
   @DoNotStrip
   private native boolean etdumpNative();
 
+  /**
+   * Dump the ExecuTorch ETDump file to {@code outputPath}.
+   *
+   * @param outputPath absolute path to write the etdump file to.
+   * @return true if the etdump was successfully written, false otherwise.
+   */
+  @Experimental
+  public boolean etdump(String outputPath) {
+    mLock.lock();
+    try {
+      if (!mHybridData.isValid()) {
+        throw new IllegalStateException("Module has been destroyed");
+      }
+      return etdumpToNative(outputPath);
+    } finally {
+      mLock.unlock();
+    }
+  }
+
+  @DoNotStrip
+  private native boolean etdumpToNative(String outputPath);
+
   /**
    * Explicitly destroys the native Module object. Calling this method is not required, as the
    * native object will be destroyed when this object is garbage-collected. However, the timing of

extension/android/jni/jni_layer.cpp

@@ -472,36 +472,51 @@ class ExecuTorchJni : public facebook::jni::HybridClass<ExecuTorchJni> {
   }
 
   jboolean etdump() {
+    return etdump_to_path("/data/local/tmp/result.etdump");
+  }
+
+  jboolean etdumpTo(facebook::jni::alias_ref<jstring> outputPath) {
+    return etdump_to_path(outputPath->toStdString().c_str());
+  }
+
+ private:
+  jboolean etdump_to_path(const char* path) {
 #ifdef EXECUTORCH_ANDROID_PROFILING
     executorch::etdump::ETDumpGen* etdumpgen =
         (executorch::etdump::ETDumpGen*)module_->event_tracer();
     auto etdump_data = etdumpgen->get_etdump_data();
 
     if (etdump_data.buf != nullptr && etdump_data.size > 0) {
-      int etdump_file =
-          open("/data/local/tmp/result.etdump", O_WRONLY | O_CREAT, 0644);
+      int etdump_file = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
       if (etdump_file == -1) {
-        ET_LOG(Error, "Cannot create result.etdump error: %d", errno);
+        ET_LOG(Error, "Cannot create %s error: %d", path, errno);
+        free(etdump_data.buf);
         return false;
       }
       ssize_t bytes_written =
           write(etdump_file, (uint8_t*)etdump_data.buf, etdump_data.size);
       if (bytes_written == -1) {
-        ET_LOG(Error, "Cannot write result.etdump error: %d", errno);
+        ET_LOG(Error, "Cannot write %s error: %d", path, errno);
+        close(etdump_file);
+        free(etdump_data.buf);
         return false;
       } else {
-        ET_LOG(Info, "ETDump written %d bytes to file.", bytes_written);
+        ET_LOG(Info, "ETDump written %zd bytes to %s.", bytes_written, path);
       }
       close(etdump_file);
       free(etdump_data.buf);
       return true;
     } else {
       ET_LOG(Error, "No ETDump data available!");
     }
+#else
+    (void)path;
 #endif
     return false;
   }
 
+ public:
+
   facebook::jni::local_ref<facebook::jni::JArrayClass<jstring>> getMethods() {
     const auto& names_result = module_->method_names();
     if (!names_result.ok()) {
@@ -571,6 +586,7 @@ class ExecuTorchJni : public facebook::jni::HybridClass<ExecuTorchJni> {
         makeNativeMethod(
             "readLogBufferStaticNative", ExecuTorchJni::readLogBufferStatic),
         makeNativeMethod("etdumpNative", ExecuTorchJni::etdump),
+        makeNativeMethod("etdumpToNative", ExecuTorchJni::etdumpTo),
         makeNativeMethod("getMethodsNative", ExecuTorchJni::getMethods),
         makeNativeMethod("getUsedBackends", ExecuTorchJni::getUsedBackends),
     });

scripts/build_android_library.sh

@@ -40,6 +40,7 @@ build_android_native_library() {
     --preset "android-${ANDROID_ABI}" \
     -DANDROID_PLATFORM=android-26 \
     -DEXECUTORCH_ENABLE_EVENT_TRACER="${EXECUTORCH_ANDROID_PROFILING:-OFF}" \
+    -DEXECUTORCH_ANDROID_PROFILING="${EXECUTORCH_ANDROID_PROFILING:-OFF}" \
     -DEXECUTORCH_BUILD_EXTENSION_LLM="${EXECUTORCH_BUILD_EXTENSION_LLM:-ON}" \
     -DEXECUTORCH_BUILD_EXTENSION_LLM_RUNNER="${EXECUTORCH_BUILD_EXTENSION_LLM:-ON}" \
     -DEXECUTORCH_BUILD_EXTENSION_ASR_RUNNER="${EXECUTORCH_BUILD_EXTENSION_LLM:-ON}" \
@@ -51,6 +52,7 @@ build_android_native_library() {
     -DQNN_SDK_ROOT="${QNN_SDK_ROOT}" \
     -DEXECUTORCH_BUILD_VULKAN="${EXECUTORCH_BUILD_VULKAN}" \
     -DXNNPACK_ENABLE_ARM_SME2="${XNNPACK_ENABLE_ARM_SME2}" \
+    -DFLATCC_ALLOW_WERROR=OFF \
     -DSUPPORT_REGEX_LOOKAHEAD=ON \
     -DCMAKE_BUILD_TYPE="${EXECUTORCH_CMAKE_BUILD_TYPE}" \
     -B"${CMAKE_OUT}"

third-party/CMakeLists.txt

@@ -91,6 +91,7 @@ ExternalProject_Add(
              -DFLATCC_TEST=OFF
              -DFLATCC_REFLECTION=OFF
              -DFLATCC_DEBUG_CLANG_SANITIZE=OFF
+             -DFLATCC_ALLOW_WERROR=OFF
              -DFLATCC_INSTALL=ON
              -DCMAKE_POLICY_VERSION_MINIMUM=3.5
              -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>