Android NDK编译报错：protobuf模块重复定义问题求助

Let's break down what's causing this error and walk through the fix step by step:

Root Cause #

Your Android.mk has a structural flaw: you started defining the ndktest module but never completed it (you skipped calling include $(BUILD_SHARED_LIBRARY) for it before moving to prebuilt libraries). Then, after setting up all prebuilt libraries, you added compiler/linker flags without first resetting the build environment with include $(CLEAR_VARS)—this caused those flags to get attached to the last prebuilt module (protobuf), triggering the "already defined" conflict.

Fixed Android.mk #

Here's the corrected version with proper module separation and complete build cycles:

LOCAL_PATH:= $(call my-dir)

# First define all prebuilt shared libraries
include $(CLEAR_VARS)
LOCAL_MODULE := c++_shared
LOCAL_SRC_FILES := $(LOCAL_PATH)/inc/build/libc++_shared.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := armnn
LOCAL_SRC_FILES := $(LOCAL_PATH)/inc/build/libarmnn.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := armnnTfParser
LOCAL_SRC_FILES := $(LOCAL_PATH)/inc/build/libarmnnTfParser.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := protobuf
LOCAL_SRC_FILES := $(LOCAL_PATH)/inc/build/libprotobuf.so
include $(PREBUILT_SHARED_LIBRARY)

# Now define your main ndktest module
include $(CLEAR_VARS)
LOCAL_MODULE := ndktest
LOCAL_SRC_FILES := ndktest.cpp

# Add compiler/linker flags and dependencies
LOCAL_LDLIBS += -lm -llog -landroid
LOCAL_CFLAGS += -DARM_NEON_64BIT -O3 -mfpu=neon -mcpu=kryo -std=c++14 -pie
LOCAL_SHARED_LIBRARIES := opencv_java3 armnn armnnTfParser protobuf c++_shared
LOCAL_C_INCLUDES := $(LOCAL_PATH)/inc/include

# Finalize the main module build
include $(BUILD_SHARED_LIBRARY)

Key Changes Explained #

• Reordered module flow: We handle all prebuilt libraries first, then our custom ndktest module. This keeps build logic isolated and avoids cross-contamination between modules.
• Complete module cycles: Every module (prebuilt or custom) now follows the full required sequence: include $(CLEAR_VARS) → set module properties → include [BUILD/PREBUILT]_SHARED_LIBRARY. This ensures each module is properly closed before moving to the next.
• Clean environment for main module: We added include $(CLEAR_VARS) right before defining ndktest, so all compiler/linker flags apply only to this module, not leftover from the last prebuilt library.

Quick Note for Application.mk #

You’re using APP_STL := gnustl_static but including c++_shared as a prebuilt library—these might conflict. If you intend to use the prebuilt libc++_shared.so, consider changing APP_STL to c++_shared instead.

内容的提问来源于stack exchange，提问作者Parag Jain