dlopen在较旧的Android版本上失败

Question

I'm loading my native library like this at runtime

dlopen("mylib.so", RTLD_LAZY);

This works fine on recent version of android (eg marshmallow, nougat, etc.). However, on older versions (eg Jellybean), this fails with the following message in logcat

Failed to load mylib.so. Error: Cannot load library: 
load_library[1093]: Library 'mylib.so' not found

I have ensured that mylib.so is part of the apk. I have this as part of x86 and armeabi_v7a architectures.

myapp.apk
- lib
  - armeabi-v7a
       mylib.so
  - x86
       mylib.so

As per readelf -d mylib.so | grep NEEDED readelf -d mylib.so | grep NEEDED the dependencies are

 0x00000001 (NEEDED)                     Shared library: [liblog.so]
 0x00000001 (NEEDED)                     Shared library: [libm.so]
 0x00000001 (NEEDED)                     Shared library: [libdl.so]
 0x00000001 (NEEDED)                     Shared library: [libc.so]

I tried loading these dependencies through dlopen prior to loading mylib.so . Though loading of those dependencies succeed, loading mylib.so always fails with the same error.

As mentioned before, I see this failure only on older versions of android.

How can I get this to work? Thanks in advance for any help.

Answer 1

Prior to Lollipop , you must supply the full path to dlopen() . This path can be obtained in Java with getApplicationInfo().nativeLibraryDir .

At any rate, you can check the contents of the /data/data/your.package/lib directory (sometimes it has -1 suffix, or starts with /data/app-lib ). This directory is world-readable, so you you should see the file libmylib.so there from Android Studio or adb shell .

Another reason for the observed behavior could be that the older device does not support armeabi-v7a ABI. That's easy to check with adb shell getprop .

Also, make sure that the library is built with the correct APP_PLATFORM , which should match the minSdkVersion .

Your library luckily does not have 'private' dependencies. But for those that do, you need to take this into account, too. Prior to Lollipop , these dependencies would not be loaded automatically (because the nativeLibraryDir was not scanned for dlopen ). You had to load all libraries in reverse dependency order.

Answer 2

尝试将文件夹名称从lib更改为jniLibs 。