undefined reference error in ndk android project using static library

Question

I'm creating a native android application in Android Studio. I downloaded GitHub eighthave/openssl-android project. I only added the row APP_ABI := armeabi-v7a to jni/Application.mk as its first row.

When I run "ndk-build" in command line it compiles libcrypto.so and libssl.so which I copied to my project's jni, libs/armeabi-v7a and jniLibs/armeabi-v7a folders. I also copied the include folder to my project's jni folder.

My project Android.mk:

LOCAL_PATH              := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE            := libcrypto
LOCAL_SRC_FILES         := libcrypto.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE            := libssl
LOCAL_SRC_FILES         := libssl.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE            := sec
LOCAL_SRC_FILES         := main.cpp application.cpp
LOCAL_CPPFLAGS          += -fexceptions -frtti -std=c++14
LOCAL_LDLIBS            := -llog -landroid -lEGL -lGLESv1_CM
LOCAL_C_INCLUDES        := ${ndkDir}/sources/android/native_app_glue
LOCAL_C_INCLUDES        += $(LOCAL_PATH)/include # openssl include folder

LOCAL_SHARED_LIBRARIES  := android_native_app_glue libcrypto libssl
include $(BUILD_SHARED_LIBRARY)

$(call import-module,android/native_app_glue)

When I run "ndk-build" from command line on my project it creates a sec.so file in the libs folder and copies the OpenSSL shared libraries next to it.

If I try to create an apk with Android Studio it throws an error:

undefined reference to 'DH_new'

at this row:

 DH dh = DH_new();

I can only compile the project in Android Studio if I do not use any functions from the openssl project. And if I do so then I can see all shared libraries in apk's "lib/armeabi-v7a" folder so it can find all the libraries.

So probably the problem could be in my build.gradle file so here it is:

apply plugin: 'com.android.model.application'

model {
    android {
        compileSdkVersion = 23
        buildToolsVersion = "23.0.3"

        defaultConfig {
            applicationId = "com.example.sec"
            minSdkVersion.apiLevel = 16
            targetSdkVersion.apiLevel = 23
        }
        ndk {
            moduleName = 'sec'
            toolchain = 'clang'
            stl = 'c++_static'
            cppFlags.addAll(['-Wall', '-std=c++14', '-fexceptions'])
            cppFlags.add("-I" + file("src/main/jni/include").absolutePath)
            ldLibs.addAll(['log', 'android'])
        }
        sources {
            main {
                jni {
                    dependencies {
                        project ':nativeactivity' linkage 'static'
                    }
                }
            }
        }
        buildTypes {
            release {
                minifyEnabled = false
                proguardFiles.add(file('proguard-rules.txt'))
            }
        }
        productFlavors{
            create("arm7") {
                ndk.abiFilters.add("armeabi-v7a")
            }
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:23.4.0'
}

And here is my Application.mk but I do not think it helps much:

APP_ABI := armeabi-v7a
APP_CPPFLAGS += -fexceptions -frtti -std=c++14
APP_STL := gnustl_static

I also tried to create static libraries from OpenSSL project but still got errors. I use gradle-experimental:0.7.0 dependency.

Can please someone help me to figure it out what could be wrong with my project. Thanks in advance!

You can't use OpenSSL directly as a shared object. You have to write a wrapper shared object that exposes all of the OpenSSL functionality you want. Your wrapper shared object links against the static version of OpenSSL. For details, see [Changing OpenSSL library in Android app for HttpClient](http://stackoverflow.com/q/28341215). You might have link problems when linking your wrapper shared object to the static version of OpenSSL, but that's a different problem. — jww, May 26 '16 at 16:44

score 0 · Accepted Answer · answered May 29 '16 at 08:23

0

I finally solved my problem. It seems that the only thing I missed is link against the shared libraries in the build.gradle file.

Like this:

ldFlags += "-L${file(path/to/libssl.so)}".toString()

ldLibs += ["ssl"]

answered May 29 '16 at 08:23

István Pecznyik

58
1
1
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I don't get it. I don't see ldFlags mentioned in the gradle-experimental specs. – IgorGanapolsky Aug 08 '16 at 18:51

undefined reference error in ndk android project using static library

1 Answers1