Question

I have source code of 2 different libraries, FooMain and FooSecondary. FooSecondary is used by FooMain, so, makefile must compile First FooSecondary, then compile FooMain, and then link FooSecondary to FooMain.

My Android.mk is:

LOCAL_PATH:= $(call my-dir)

# Foo Secondary lib:

# Clear vars
include $(CLEAR_VARS)
# Target Build
LOCAL_ARM_MODE := arm   
# Library Name          
LOCAL_MODULE := FooSecondary        
# Set All SRC_FILES Together            
SRC_FILES := $(wildcard $(LOCAL_PATH)/FooSecondary/src/*.c)
SRC_FILES := $(SRC_FILES:$(LOCAL_PATH)/%=%)     
LOCAL_SRC_FILES = $(SRC_FILES)
# Enable Log support
LOCAL_LDLIBS = -llog    
# C   Flags - Max optimization              
LOCAL_CFLAGS := -O3 -mno-thumb
# C++ Flags - Max optimization          
LOCAL_CPPFLAGS := -O3 -mno-thumb
# Compile as Shared Library     
include $(BUILD_SHARED_LIBRARY)     

# Foo Secondary lib:

# Clear vars
include $(CLEAR_VARS)
# Include OpenCV
include 3rdparty/OpenCV-2.4.3-rc-android-sdk/sdk/native/jni/OpenCV.mk
# Target Build
LOCAL_ARM_MODE := arm   
# Library Name          
LOCAL_MODULE := FooMain     
# Set All SRC_FILES Together            
SRC_FILES := $(wildcard $(LOCAL_PATH)/FooMain/src/*.cpp)
SRC_FILES := $(SRC_FILES:$(LOCAL_PATH)/%=%)     
LOCAL_SRC_FILES = $(SRC_FILES)
LOCAL_SHARED_LIBRARIES := libFooSecondary
LOCAL_LDLIBS := -L$(LOCAL_PATH)/../libs/armeabi 
LOCAL_LDLIBS += -lz -lm -ldl -lGLESv2 -lEGL -llog -lFooSecondary
LOCAL_CFLAGS := -O2 -mno-thumb -Wno-write-strings
LOCAL_CPPFLAGS := -O2 -mno-thumb -Wno-write-strings
# Compile as Shared Library     
include $(BUILD_SHARED_LIBRARY) 

And my Application.mk is:

APP_CPPFLAGS := -frtti -fexceptions
APP_STL := gnustl_static
APP_ABI := armeabi-v7a

But, when I compile Android.mk using ndk-build I get the next Error:

Compile arm    : libFooSecondary <= *.c
SharedLibrary  : libFooSecondary.so
Install        : libFooSecondary.so => libs/armeabi-v7a/libFooSecondary.so
SharedLibrary  : libFooMain.so

/home/user/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/bin/../lib/gcc/arm-linux-androideabi/4.4.3/../../../../arm-linux-androideabi/bin/ld: cannot find -lFooSecondary

collect2: ld returned 1 exit status
make: *** [obj/local/armeabi-v7a/libFooMain.so] Error 1

Why libFooSecondary.so is not found if is correctly compiled and installed?

Additionaly, if LOCAL_MODULE name change, for example, first one is LOCAL_MODULE := zname and second one is LOCAL_MODULE := aname, compile first the second one, i don’t know why.

Answer 1

Your Android.mk looks weird. Does it assign LOCAL_PATH somewhere? There is no need to assign LOCAL_CPPFLAGS to duplicate LOCAL_CFLAGS, because ndk-build puts both sets of flags on C++ command line.

To understand better how NDK interprets your Application.mk and Android.mk, you can run

ndk-build V=1

This will echo all executed commands, including compilation and link, with all their parameters that NDK build assigns.