Question

I am attempting to compile an Android-9 project that calls Android NDK functions (such as “AAsset_close”) by running “ndk-build” via the Cygwin terminal, but the “ndk-build” command returns an error message, stating that it is unable to find the function definitions.

The error messages from “ndk-build” are as follows:

[Android NDK path]/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: [project folder]/static library: in function [function name]:[file name]:39: error: undefined reference to ‘AAsset_close’

etc.

My “Android.mk” file is as follows:

LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)

LOCAL_MODULE    := <name of project>
LOCAL_C_INCLUDES := <folders where header files are located>
LOCAL_CFLAGS := $(LOCAL_C_INCLUDES:%=-I%) -O2 -Wall -D__ANDROID__ -DtyANDROID
LOCAL_CPPFLAGS := $(LOCAL_C_INCLUDES:%=-I%) -O2 -Wall -D__ANDROID__ -DtyANDROID
LOCAL_LDLIBS := -lm -lEGL -lGLESv2 -llog -lz -landroid
LOCAL_STATIC_LIBRARIES := android_native_app_glue

LOCAL_ARM_MODE  := arm  

LOCAL_SRC_FILES := <source files>

include $(BUILD_STATIC_LIBRARY)
...

My “Application.mk” makefile is as follows:

APP_ABI := armeabi armeabi-v7a x86
APP_PLATFORM := android-9

According to the “nm” Unix command, this function is defined within the Android NDK library “libandroid.so”, which is present in the NDK path for all target platforms. As demonstrated above, I have included “-landroid” to the “LOCAL_LDLIBS” macro, which should allow me to link against that library. What else do I need to do to fix this compile error?

Answer 1

You show the Android.mk that builds a static library, at this step the linker is not called, threfore $(LOCAL_LDLIBS) is ignored. You probably have another Android.mk or a different section, where you have

include $(BUILD_SHARED_LIBRARY)  

Please check, -landroid is probably missing in that section.