Android NDK UnsatisfiedLinkError: "dlopen failed: empty/missing DT_HASH"

Question

I am tracking down crashes with our Android application (which uses the NDK to load a custom C++ library) using a crash reporting service. A small number of users are experiencing the following crash:

java.lang.UnsatisfiedLinkError: dlopen failed: empty/missing DT_HASH in "cpplibrary.so" (built with --hash-style=gnu?)
   at java.lang.Runtime.loadLibrary(Runtime.java:365)
   at java.lang.System.loadLibrary(System.java:526)

The couple of mentions of this error I can find on the internet (for example this Google Groups post) discuss problems with building the libs, which cause this error to occur every time the app is run. There is little information on why this might happen sporadically. This post is the closest I can find.

Based on the crash traces, it looks like any particular user will experience this constantly for stretches; I am not sure if these users are ever able to load the lib correctly. Does anyone have ideas on what might cause this to happen only sometimes? Can I do the NDK build differently to try and stop it?

Thanks!

Edit: This post mentions two ways to get such errors conditionally; I will be looking in to them.

Edit2: Build files: Android.mk (excerpt):

include $(CLEAR_VARS)
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)
LOCAL_C_INCLUDES := <Source Path>...
LOCAL_CFLAGS := -DANDROID -Wall
LOCAL_CPPFLAGS := -DENABLE_SDK_DEBUGGING=1 -DENABLE_SDK_LOGGING=1
LOCAL_MODULE := cpplibrary
LOCAL_SRC_FILES := <Source Files> / ...

LOCAL_LDLIBS    := -llog -landroid
LOCAL_STATIC_LIBRARIES := cpplibrary
include $(BUILD_SHARED_LIBRARY)

Application.mk:

APP_STL := stlport_static
APP_CFLAGS += -std=c++11

Answer 1

If you're a third party building .so libraries for others to use, setting -Wl,--hash-style=both seems like the best idea. That gets you the faster loading of the Gnu-style hash and the backwards compatibility of the SysV hash.

If you're only supporting Android 8 and later, there's no need to support the SysV hash.

Answer 2

The library you are trying to load was most likely built with -Wl,--hash-style=gnu. This was not supported on Android until recently (afaik this isn't even in L). You need to build your libraries with -Wl,--hash-style=sysv.

How did you build cpplibrary.so? If you didn't do anything to manually switch to the gnu hash style, it could be a bug in the NDK.

Answer 3

I have faced this problem while using Android Cmake and I have set -DANDROID_PLATFORM=23 As per changelog The GNU hash style becomes available from API 23 and because of ANDROID_PLATFORM was set to 23 the flag --hash-style=gnu was set automatically.

I have fixed this just by lowering -DANDROID_PLATFORM=21and then the flag was set to the flag --hash-style=both

Answer 4

Although out of this question, I met this problem in Android Studio import third-party so file. Finally I found this is because Gradle automatically stripped the product 'so' file, so disabling this option it works.

android {
	........
    packagingOptions{
        doNotStrip "*/armeabi-v7a/*.so"
    }
   .......
}