未定义引用错误，不能创建共享库 [英] Undefined reference error, can not create shared library
问题描述
试了很多方法来解决问题，但没有运气。这里是我的Android.mk：
Tried so many ways to solve problem but no luck. Here is my Android.mk:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := avcodec
LOCAL_SRC_FILES :=libavcodec.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := avutil
LOCAL_SRC_FILES :=libavutil.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := swscale
LOCAL_SRC_FILES :=libswscale.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := avformat
LOCAL_SRC_FILES :=libavformat.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := avresample
LOCAL_SRC_FILES :=libavresample.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := swresample
LOCAL_SRC_FILES :=libswresample.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := x264
LOCAL_SRC_FILES :=libx264.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
#------------------------------------------
LOCAL_C_INCLUDES := $(LOCAL_PATH)\
$(LOCAL_PATH)/include
LOCAL_MODULE := media
LOCAL_SRC_FILES := \
P_Decoding.cpp \
P_Encoding.cpp \
wrapper_for_ffmpeg.cpp
LOCAL_CPPFLAGS := -std=c++11 -pthread -frtti -fexceptions
LOCAL_ARM_MODE := arm
LOCAL_STATIC_LIBRARIES := avcodec avutil swscale avformat avresample swresample x264
LOCAL_LDLIBS := -llog -ljnigraphics -landroid -lz -lEGL
LOCAL_CPP_FEATURES := rtti exceptions
include $(BUILD_SHARED_LIBRARY)
在JNI文件夹下有到.CPP关于makefile文件相关的所有头.HPP文件，也有所有静态.A库和包括文件夹中涉及到的静态库中的所有头文件。我使用ndk9c版本。
下面是错误日志的一部分：
In jni folder there are all header .hpp files related to .cpp files on makefile, also there are all static .a libraries and "include" folder where all header files related to static libraries are. I'm using ndk9c version. Here is part of error log:
[armeabi-v7a] Compile++ thumb: media <= P_Decoding.cpp
[armeabi-v7a] Compile++ thumb: media <= P_Encoding.cpp
[armeabi-v7a] Compile++ thumb: media <= wrapper_for_ffmpeg.cpp
/home/pro/android-ndk-r9c/toolchains/llvm-3.3/$p$pbuilt/linux-x86/bin/clang++轮候册，-soname，libmedia.so -shared --sysroot = /家庭/ PRO / Android的NDK-R9C /平台/ Android的9 /弓臂./obj/local/armeabi/objs/media/P_Decoding.o ./obj/local/armeabi/objs/media/P_Encoding.o JNI / libavformat流.A JNI / libav codec.a JNI / libavutil.a JNI / libswscale.a -lgcc ./obj/local/armeabi/libgnustl_shared.so -gcc工具链的/ home / PRO / Android的NDK-R9C /工具链/arm-linux-androideabi-4.8/$p$pbuilt/linux-x86 -no-canonical- prefixes -target的ARMv5TE-NONE-Linux的androideabi轮候册， - 没有不确定-Wl，-z，noexecstack -Wl，-z，relro -Wl，-z，现在-L /家庭/ PRO / Android的NDK-R9C /平台/ Android的9 /弓臂/ usr / lib目录-llog -ljnigraphics -lz -ldl -lgcc /home/pro/android-ndk-r9c/sources/cxx-stl/gnu-libstdc++/4.8/libs/armeabi/libsupc++.a -lc -lm -o ./obj/local/armeabi/libmedia.so
/home/pro/android-ndk-r9c/toolchains/llvm-3.3/prebuilt/linux-x86/bin/clang++ -Wl,-soname,libmedia.so -shared --sysroot=/home/pro/android-ndk-r9c/platforms/android-9/arch-arm ./obj/local/armeabi/objs/media/P_Decoding.o ./obj/local/armeabi/objs/media/P_Encoding.o jni/libavformat.a jni/libavcodec.a jni/libavutil.a jni/libswscale.a -lgcc ./obj/local/armeabi/libgnustl_shared.so -gcc-toolchain /home/pro/android-ndk-r9c/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86 -no-canonical-prefixes -target armv5te-none-linux-androideabi -Wl,--no-undefined -Wl,-z,noexecstack -Wl,-z,relro -Wl,-z,now -L/home/pro/android-ndk-r9c/platforms/android-9/arch-arm/usr/lib -llog -ljnigraphics -lz -ldl -lgcc /home/pro/android-ndk-r9c/sources/cxx-stl/gnu-libstdc++/4.8/libs/armeabi/libsupc++.a -lc -lm -o ./obj/local/armeabi/libmedia.so
jni/P_Decoding.cpp:10: error: undefined reference to 'avcodec_register_all'
jni/P_Decoding.cpp:17: error: undefined reference to 'avcodec_find_decoder'
jni/P_Decoding.cpp:14: error: undefined reference to 'avcodec_find_decoder_by_name'
jni/P_Decoding.cpp:24: error: undefined reference to 'avcodec_alloc_context3'
jni/P_Decoding.cpp:50: error: undefined reference to 'avcodec_open2'
jni/P_Decoding.cpp:56: error: undefined reference to 'avcodec_alloc_frame'
jni/P_Decoding.cpp:76: error: undefined reference to 'sws_getContext'
jni/P_Decoding.cpp:90: error: undefined reference to 'avcodec_decode_video2'
jni/P_Decoding.cpp:104: error: undefined reference to 'sws_scale'
jni/P_Decoding.cpp:118: error: undefined reference to 'avcodec_close'
任何帮助，请。在此先感谢
Any help please. Thanks in advance
推荐答案
请确保您已经添加了的externC围绕包括libav $ C $的块CC和swscale头，如像这样的：
Make sure you have added the extern "C" block around the include of the libavcodec and swscale headers, e.g. like this:
extern "C" {
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>
}
See https://libav.org/faq.html#I_0027m-using-Libav-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e for documentation that explains this.
编辑：另外，你确定了prebuilt libav codec.a是相同的体系结构（armeabi-V7A）为你建立？如果您正在为多种架构（armeabi-V7A，X86等）的共享库，你需要有prebuilt库的多个版本的对应也。
Also, are you sure that the prebuilt libavcodec.a is for the same architecture (armeabi-v7a) as you're building? If you are building your shared library for multiple architectures (armeabi-v7a, x86, etc) you need to have multiple corresponding versions of the prebuilt libraries as well.
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