Develop Reference

incompatible target while building apk for Native Android Project

I am trying to implement Alexa Voice Service SDK in Android.
I have pre-build libraries, which i am using in my Android Project.
I have .so files under src/main/jniLibs/armeabi-v7a/*.so
I can successfully compile and build apk for x86 platform , but my target is run it on armeabi-v7a device.
but while generating apk i am facing the incompatible target error.
the full error is shown below ,
FAILURE: Build failed with an exception.
What went wrong:
Execution failed for task ':app:externalNativeBuildDebug'.
> Build command failed.
Error while executing process /home/ajinkya/Androidsdk/cmake/3.10.2.4988404/bin/cmake with arguments {--build /root/AndroidStudioProjects/alexaProtoApp/app/.externalNativeBuild/cmake/debug/armeabi-v7a --target native-lib}
[1/2] Building CXX object CMakeFiles/native-lib.dir/native-lib.cpp.o
[2/2] Linking CXX shared library /root/AndroidStudioProjects/alexaProtoApp/app/build/intermediates/cmake/debug/obj/armeabi-v7a/libnative-lib.so
FAILED: /root/AndroidStudioProjects/alexaProtoApp/app/build/intermediates/cmake/debug/obj/armeabi-v7a/libnative-lib.so
: && /home/ajinkya/Androidsdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++ --target=armv7-none-linux-androideabi24 --gcc-toolchain=/home/ajinkya/Androidsdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64 --sysroot=/home/ajinkya/Androidsdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/sysroot -fPIC -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -fno-addrsig -march=armv7-a -mthumb -Wa,--noexecstack -Wformat -Werror=format-security -O0 -fno-limit-debug-info -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libatomic.a -static-libstdc++ -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--exclude-libs,libunwind.a -Wl,--no-undefined -Qunused-arguments -Wl,-z,noexecstack -shared -Wl,-soname,libnative-lib.so -o /root/AndroidStudioProjects/alexaProtoApp/app/build/intermediates/cmake/debug/obj/armeabi-v7a/libnative-lib.so CMakeFiles/native-lib.dir/native-lib.cpp.o /root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/../../main/jniLibs/armeabi-v7a/libSampleApp.so /home/ajinkya/Androidsdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/arm-linux-androideabi/24/liblog.so /home/ajinkya/Androidsdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/arm-linux-androideabi/24/liblog.so -latomic -lm && :
/home/ajinkya/Androidsdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/bin/ld: error: /root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/../../main/jniLibs/armeabi-v7a/libSampleApp.so: incompatible target
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:25: error: undefined reference to 'my_initialize(_JavaVM*, _jobject*)'
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:31: error: undefined reference to 'jni_wakeAlexa()'
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:37: error: undefined reference to 'jni_wakeWithHoldAlexa()'
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:43: error: undefined reference to 'jni_resetAlexa()'
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:49: error: undefined reference to 'jni_reauthorizeAlexa()'
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:55: error: undefined reference to 'jni_quitAlexa()'
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:61: error: undefined reference to 'jni_infoAlexa()'
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.
My build.gradle like,
apply plugin: 'com.android.application'
android {
compileSdkVersion 29
defaultConfig {
applicationId "my.project.vdi"
minSdkVersion 24
targetSdkVersion 29
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
multiDexEnabled true
externalNativeBuild {
cmake {
cppFlags ""
// abiFilters "armeabi-v7a"
// arguments "-DANDROID_ARM_MODE=arm" , "-DANDROID_TOOLCHAIN=clang"
}
}
ndk {
// Specifies the ABI configurations of your native
// libraries Gradle should build and package with your APK. , x86 , armeabi-v7a
abiFilters "armeabi-v7a"
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "src/main/cpp/CMakeLists.txt"
version "3.10.2"
}
}
sourceSets {
main {
jni.srcDirs = []
// let gradle pack the shared library into apk
jniLibs.srcDirs = ['src/main/jniLibs/']
}
}
// packagingOptions {
// exclude 'lib/arm64-v8a/libnative-lib.so'
// exclude 'lib/x86_64/libnative-lib.so'
// exclude 'lib/x86/libnative-lib.so'
// }
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'androidx.appcompat:appcompat:1.0.2'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'androidx.test:runner:1.2.0'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
implementation 'com.squareup.picasso:picasso:2.5.2'
}
ALso the CMakeLists.txt
cmake_minimum_required(VERSION 3.4.1)
add_library( # Sets the name of the library.
native-lib
SHARED
native-lib.cpp)
add_library(SampleApp SHARED IMPORTED)
set_target_properties(SampleApp PROPERTIES IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/../../main/jniLibs/${ANDROID_ABI}/libSampleApp.so)
find_library(
log-lib
log)
find_library(ANDROID_LOG_LIB log)
target_link_libraries(
native-lib
SampleApp
${ANDROID_LOG_LIB}
${log-lib} )
Please guide me resolving this issue.

.../armeabi-v7a/libSampleApp.so: incompatible target
That library isn't actually built for armeabi-v7a. The following should tell you what it is:
$ file /root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/../../main/jniLibs/armeabi-v7a/libSampleApp.so
Here's example output from libc++_shared.so in the NDK:
$ file android-ndk-r21-canary/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/arm-linux-androideabi/libc++_shared.so
android-ndk-r21-canary/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/arm-linux-androideabi/libc++_shared.so: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, BuildID[sha1]=4dc00a833014c1ddd2e1ec64c5dd72237c4179ee, with debug_info, not stripped
The interesting part is:
ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV)

I got the solution, it is very unusual for me , the .so files which were generating while compiling, were not getting replaced. the old version of the files were not getting updated by the new ones. I deleted the folder and then compiled and the new files generated were the proper ones.

How to resolve Android ndk build command faild?

I am developing simple ndk sample example using android ndk in android studio. While running my app studio shows below errors.
Build command failed.
Error while executing process D:\Sdk\cmake\3.6.4111459\bin\cmake.exe with
arguments {--build D:\Android Studio\Workspace\NDKSample\app\.externalNativeBuild\cmake\debug\arm64-v8a --target native-lib}
[1/2] Building CXX object CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.oFAILED: D:\Sdk\ndk-bundle\toolchains\llvm\prebuilt\windows-x86_64\bin\clang++.exe --target=aarch64-none-linux-android --gcc-toolchain=D:/Sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/windows-x86_64 --sysroot=D:/Sdk/ndk-bundle/sysroot -Dnative_lib_EXPORTS -isystem D:/Sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/include -isystem D:/Sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/libs/arm64-v8a/include -isystem D:/Sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/include/backward -isystem D:/Sdk/ndk-bundle/sysroot/usr/include/aarch64-linux-android -D__ANDROID_API__=21 -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -Wa,--noexecstack -Wformat -Werror=format-security -frtti -fexceptions -O0 -fno-limit-debug-info -fPIC -MD -MT CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o -MF CMakeFiles\native-lib.dir\src\main\cpp\native-lib.cpp.o.d -o CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o -c "D:\Android Studio\Workspace\NDKSample\app\src\main\cpp\native-lib.cpp"
error: error reading 'D:\Android Studio\Workspace\NDKSample\app\src\main\cpp\native-lib.cpp'
1 error generated.ninja: build stopped: subcommand failed.
I have search lot but not able to find proper answer that why I am asking here. I have also unintsall all the components and re-install on my studio still error is there.
Another thing If I change file extension to .C from .CPP whole project gets complied and even runs properly. I don't know why Its not working for .CPP file.
Components I am using.
Android Stuido - 3.1.3
gradle - 3.1.0
cmake - 3.6.4111459
Android ndk - 17.1.4828580
lldb -3.1
native-lib.cpp
#include <jni.h>#include <string>extern "C" JNIEXPORT jstringJNICALLJava_com_mastek_ndksample_MainActivity_stringFromJNI(
JNIEnv *env,
jobject /* this */) {
std::string hello = "Hello from C++";
return env->NewStringUTF(hello.c_str());}
build.gradle
apply plugin: 'com.android.application'android { compileSdkVersion 27
defaultConfig {
applicationId "com.example.ndksample"
minSdkVersion 15
targetSdkVersion 27
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
externalNativeBuild {
cmake {
cppFlags "-frtti -fexceptions"
}
}
}
sourceSets {
main {
jniLibs.srcDirs = ['src/main/jniLibs']
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}}dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:27.1.1'
implementation 'com.android.support.constraint:constraint-layout:1.1.2'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'}
Anyone know please help me to solve this problem. Thanks in advance.

NDK build fails miserably when the path to project files contains spaces. To fix your build, copy the project to path without spaces.

After lot of trials and help from github google guy I am able to solve. To resolve problem I have follow below steps.
1.go to project directory.
2.deleted .gradle ,app/.externalNativeBuild and app/build.
3.changed local.properties ndk path to external ndk-r16b.
4.Run through Android studio.
5.Finally apk is generate.

Undefined reference when calling a OpenCL function in Android

I am trying to set a simple project in Android Studio with OpenCL. So I created a new project with NDK support and an empty activity. I have copied the libOpenCL.so from my mobile phone to the folder app\src\main\jniLibs\arm8 and I have downloaded the OpenCL headers from the Khronos webpage and copied them to app\src\main\jni\CL. Furthermore, I have done two modifications to the build.gradle file, I have added a parameter to the cppFlags to include the OpenCL folder and I have set an abi filter to build only for arm8. I copy my build.gradle file here:
apply plugin: 'com.android.application'
android {
compileSdkVersion 26
buildToolsVersion "26.0.1"
defaultConfig {
applicationId "es.um.mompes.testopencl"
minSdkVersion 22
targetSdkVersion 26
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
externalNativeBuild {
cmake {
cppFlags "-std=c++11 -fexceptions -I${projectDir}/src/main/jni"
}
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}
productFlavors {
arm8 {
ndk {
abiFilter "arm64-v8a"
}
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support.constraint:constraint-layout:1.0.2'
testCompile 'junit:junit:4.12'
}
I have also added a three lines to the generated native-lib.cpp file to test if OpenCL is working. This is my native-lib.cpp:
#include <jni.h>
#include <string>
#include <CL/cl.h>
extern "C"
JNIEXPORT jstring JNICALL
Java_es_um_mompes_testopencl_MainActivity_stringFromJNI(
JNIEnv *env,
jobject /* this */) {
std::string hello = "Hello from C++";
cl_int err;
// Find the number of OpenCL platforms
cl_uint num_platforms;
err = clGetPlatformIDs(0, NULL, &num_platforms);
return env->NewStringUTF(hello.c_str());
}
However, I must be missing something because I am getting an undefined reference error regarding the OpenCL function when I build the project. This is the complete error:
Execution failed for task ':app:externalNativeBuildArm8Debug'.
Build command failed.
Error while executing process C:\Users\Juan\AppData\Local\Android\Sdk\cmake\3.6.4111459\bin\cmake.exe with arguments {--build C:\Users\Juan\AndroidStudioProjects\TestOpenCL\app.externalNativeBuild\cmake\arm8Debug\arm64-v8a --target native-lib}
[1/1] Linking CXX shared library ........\build\intermediates\cmake\arm8\debug\obj\arm64-v8a\libnative-lib.so
FAILED: cmd.exe /C "cd . && C:\Users\Juan\AppData\Local\Android\sdk\ndk-bundle\toolchains\llvm\prebuilt\windows-x86_64\bin\clang++.exe --target=aarch64-none-linux-android --gcc-toolchain=C:/Users/Juan/AppData/Local/Android/sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/windows-x86_64 --sysroot=C:/Users/Juan/AppData/Local/Android/sdk/ndk-bundle/sysroot -fPIC -isystem C:/Users/Juan/AppData/Local/Android/sdk/ndk-bundle/sysroot/usr/include/aarch64-linux-android -D__ANDROID_API__=22 -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -Wa,--noexecstack -Wformat -Werror=format-security -std=c++11 -fexceptions -IC:\Users\Juan\AndroidStudioProjects\TestOpenCL\app/src/main/jni -O0 -fno-limit-debug-info -Wl,--exclude-libs,libgcc.a --sysroot C:/Users/Juan/AppData/Local/Android/sdk/ndk-bundle/platforms/android-22/arch-arm64 -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -shared -Wl,-soname,libnative-lib.so -o ........\build\intermediates\cmake\arm8\debug\obj\arm64-v8a\libnative-lib.so CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o -llog -lm "C:/Users/Juan/AppData/Local/Android/sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/libs/arm64-v8a/libgnustl_static.a" && cd ."
CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o: In function Java_es_um_mompes_testopencl_MainActivity_stringFromJNI':
C:\Users\Juan\AndroidStudioProjects\TestOpenCL\app\src\main\cpp/native-lib.cpp:14: undefined reference toclGetPlatformIDs'
clang++.exe: error: linker command failed with exit code 1 (use -v to see invocation)
Do you know what am I missing? I've searching for a few hours over the last two days about how to setup OpenCL in Android Studio but everything I find seems to be outdated and doesn't seem to work for my problem.

Look for Android.mk under jni folder. Then add this:
LOCAL_PATH := $(call my-dir) // should already be there
.
.
LOCAL_LDLIBS := $(LOCAL_PATH)/libOpenCL.so
This example takes the libOpenCL.so from the jni root but you can change this for your needs.
Reference: Getting Started with OpenCL on Android

I would recommend you replace the automatic Android Studio NDK building with your own so you have total control.
Then you can use #RonTLV answer to add the library to the Android.mk and have a proper build.
Android Studio by default ignores Android.mk and generates its own with all the .c/.cpp files in the jni folder.
sourceSets {
debug.jniLibs.srcDir 'src/main/obj/local' //debug builds have symbols
release.jniLibs.srcDir 'src/main/libs' //release builds have cleaned libraries
main.jni.srcDirs = [] //disable automatic ndk-build call with auto-generated Android.mk
}
// call regular ndk-build script manually
task ndkBuild(type: Exec) {
if (System.properties['os.name'].toLowerCase(Locale.ROOT).contains('windows')) {
commandLine 'ndk-build.cmd', '-j8', '-C', file('src/main').absolutePath
} else {
commandLine 'ndk-build', '-j8', '-C', file('src/main').absolutePath
}
}
//Make the NDK task depend on Java build Task
tasks.withType(JavaCompile) {
compileTask -> compileTask.dependsOn ndkBuild
}

Android Studio CMake Error: Build Command failed

I'm running into an Error when I open a new project in Android Studio from the Code Samples (Hello JIN). When the Project is opened the following:
Build command failed.
Error while executing process /opt/android-sdk/cmake/3.6.4111459/bin/cmake with arguments {-H/home/max/Documents/AndroidStudioProjects/HelloJNI1/app/src/main/cpp -B/home/max/Documents/AndroidStudioProjects/HelloJNI1/app/.externalNativeBuild/cmake/arm8Release/arm64-v8a -GAndroid Gradle - Ninja -DANDROID_ABI=arm64-v8a -DANDROID_NDK=/opt/android-sdk/ndk-bundle -DCMAKE_LIBRARY_OUTPUT_DIRECTORY=/home/max/Documents/AndroidStudioProjects/HelloJNI1/app/build/intermediates/cmake/arm8/release/obj/arm64-v8a -DCMAKE_BUILD_TYPE=Release -DCMAKE_MAKE_PROGRAM=/opt/android-sdk/cmake/3.6.4111459/bin/ninja -DCMAKE_TOOLCHAIN_FILE=/opt/android-sdk/ndk-bundle/build/cmake/android.toolchain.cmake -DANDROID_PLATFORM=android-23 -DANDROID_TOOLCHAIN=clang}
-- Check for working C compiler: /opt/android-sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang
-- Check for working C compiler: /opt/android-sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang -- broken
-- Configuring incomplete, errors occurred!
See also "/home/max/Documents/AndroidStudioProjects/HelloJNI1/app/.externalNativeBuild/cmake/arm8Release/arm64-v8a/CMakeFiles/CMakeOutput.log".
See also "/home/max/Documents/AndroidStudioProjects/HelloJNI1/app/.externalNativeBuild/cmake/arm8Release/arm64-v8a/CMakeFiles/CMakeError.log".
CMake Error at /opt/android-sdk/cmake/3.6.4111459/share/cmake-3.6/Modules/CMakeTestCCompiler.cmake:61 (message):
The C compiler
"/opt/android-sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang"
is not able to compile a simple test program.
It fails with the following output:
Change Dir: /home/max/Documents/AndroidStudioProjects/HelloJNI1/app/.externalNativeBuild/cmake/arm8Release/arm64-v8a/CMakeFiles/CMakeTmp
Run Build Command:"/opt/android-sdk/cmake/3.6.4111459/bin/ninja"
"cmTC_0053d"
[1/2] Building C object CMakeFiles/cmTC_0053d.dir/testCCompiler.c.o
FAILED:
/opt/android-sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang
--target=aarch64-none-linux-android
--gcc-toolchain=/opt/android-sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64
--sysroot=/opt/android-sdk/ndk-bundle/sysroot -isystem
/opt/android-sdk/ndk-bundle/sysroot/usr/include/aarch64-linux-android
-D__ANDROID_API__=23 -g -DANDROID -ffunction-sections -funwind-tables
-fstack-protector-strong -no-canonical-prefixes -Wa,--noexecstack -Wformat
-Werror=format-security -fPIE -o
CMakeFiles/cmTC_0053d.dir/testCCompiler.c.o -c
/home/max/Documents/AndroidStudioProjects/HelloJNI1/app/.externalNativeBuild/cmake/arm8Release/arm64-v8a/CMakeFiles/CMakeTmp/testCCompiler.c
/opt/android-sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang:
error while loading shared libraries: libncurses.so.5: cannot open shared
object file: No such file or directory
ninja: build stopped: subcommand failed.
CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
CMakeLists.txt
This Error drops mutliple times in the IDE
I'm using Arch-Linux 64x
Cmake.txt:
cmake_minimum_required(VERSION 3.4.1)
add_library(hello-jni SHARED
hello-jni.c)
# Include libraries needed for hello-jni lib
target_link_libraries(hello-jni
android
log)

Build -> Refresh Linked C++ Projects resolved this error for me.

I found this Solution Online and this worked, however there was no explanation on how it worked:
Remove the following block of code from you build.gradle file:
externalNativeBuild {
cmake {
path "src/main/cpp/CMakeLists.txt"
}
}

#rpurohit was nearly right, Clang isn't working properly. But to change the Compiler you need to change build.gradle, in my build.gradle it was Line 12:
apply plugin: 'com.android.application'
1 android {
2 compileSdkVersion 25
3 buildToolsVersion '25.0.2'
4 defaultConfig {
5 applicationId 'com.example.hellojni'
6 minSdkVersion 23
7 targetSdkVersion 25
8 versionCode 1
9 versionName "1.0"
10 externalNativeBuild {
11 cmake {
12 arguments '-DANDROID_TOOLCHAIN=clang' --> gcc
}
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "src/main/cpp/CMakeLists.txt"
}
}
productFlavors {
arm7 {
// in the future, ndk.abiFilter might also work
ndk {
abiFilter 'armeabi-v7a'
}
}
arm8 {
ndk {
abiFilters 'arm64-v8a'
}
}
arm {
ndk {
abiFilter 'armeabi'
}
}
x86 {
ndk {
abiFilter 'x86'
}
}
x86_64 {
ndk {
abiFilter 'x86_64'
}
}
mips {
ndk {
abiFilters 'mips', 'mips64'
}
}
universal {
ndk {
abiFilters 'mips', 'mips64', 'x86', 'x86_64'
}
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:25.2.0'
compile 'com.android.support.constraint:constraint-layout:1.0.1'
}

I would recommend using GCC instead of clang for the time being because clang still does not contain all features. You can change your compiler by doing the following:
set(CMAKE_C_COMPILER /path-to-ndk/toolchains/aarch64-linux-android-4.9/prebuilt/darwin-x86_64/bin/aarch64-linux-android-gcc)
However, the darwin-x86_64 directory only exists if you are on a Mac. If you are on another platform, just use the directory that exists under the prebuilt folder.

I encountered this problem because I set the wrong path of native-lib.cpp. After changing
add_library(native-lib SHARED native-lib.cpp)
to
add_library(native-lib SHARED src/main/jni/native-lib.cpp)
it worked again.
By the way, this is part of my project's structure.
CMakeLists.txt
src
|__main
|___jni
|___native-lib.cpp

In case previous answer doesn't work for you, as it happened to me, try to fix permissions in the bin folder of cmake and for ndk. In my case: C:\android-sdk\cmake\3.6.4111459\bin and c:\android-sdk\ndk-bundle
In my case Users group did had no permissions so Android Studio wasn't able to run cmake. Make sure it has Read and execution permissions.

This error sometimes occurs when you upgrade gradle or other dependencies.
a simple solution is Build > "Refresh linked C++ project" and after that rebuilding your project. everything goes right

I tried the solutions provided above but no luck. Then I changed the path of OpenCV_DIR which was set in the CMakeLists.txt file and it worked. My project was not pointing to the right path, which was causing the error. Make sure you have provided the right path in your CMakeLists.txt file.
For example :
set(OpenCV_DIR "...../OpenCV_Android/install/sdk/native/jni/abi-arm64-v8a")

I find this way can work:
not need delete below:
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}
this is useful .and your project just less the ninja file .
you can fllow this way can build successful!
here is the result:
Make was unable to find a build program corresponding to "Ninja". CMAKE_MAKE_PROGRAM is not set. You probably need to select a different build tool.
you should install ninja
download ninja here ninja download file
get the ninja file
copy the ninja file to the /usrlocal/bin
build again .the project run successfull!!

How to get verbose output for undefined reference error using -v in clang (Android-Studio)

Whenever you get a linker error in Android Studio it suggests you to use -v to see invocation, but where to put the -v command to get the "verbose output" (according to llvm clang command guide)?
Already tried:
externalNativeBuild {
cmake {
cppFlags "-frtti -fexceptions -v"
}
}
which is not changing anything in the output as far as i noticed and
--stacktrace --debug
in
Settings > Compiler > Command-line Options
Which is showing way more output but not what I am looking for!
Thank you very much for your help in advance!
EDIT
Since i am compiling C files i obviously had to use cFlags. Now the gradle file looks as follows (thx to #Alex Cohn):
apply plugin: 'com.android.application'
android {
compileSdkVersion 25
buildToolsVersion "25.0.3"
defaultConfig {
applicationId "<my_id>"
minSdkVersion 16
targetSdkVersion 25
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
externalNativeBuild {
cmake {
cFlags "-v"
}
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:25.3.1'
compile 'com.android.support.constraint:constraint-layout:1.0.1'
testCompile 'junit:junit:4.12'
}
EDIT 2
Adding following pre-processor command in a few C-classes i did not notice they were missing it, i was able to get rid of my linker error about the missing reference:
#ifdef __cplusplus
extern "C"
{
#endif
// your includes and your code here
#ifdef __cplusplus
}
#endif

cppFlags "-frtti -fexceptions -v" works as well as cppFlags "-frtti", "-fexceptions", "-v" for clang++ tasks, that is, to get verbose output for .cpp or .cxx files compilation.
cFlags "-v" works to produce verbose output for .c files compilation.
To produce verbose output for link step, edit your CMakeLists.txt file, add -v to the relevant target_link_libraries statement, e.g.
target_link_libraries(myjnilib android log -v)
All above may not be enough to understand and fix undefined reference error.