How to compile two different libraries in same Android.mk linking one of them to other

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.

ndk-build works in the following order: first, it compiles all files that belong to the last project. Then it "understands" that it needs another project, on which the last project depends (e.g. via LOCAL_SHARED_LIBRARIES), and starts building it. If it does not have other dependencies, NDK can link the second library, and after that - the first. Bit if there are more dependencies, the same "algorithm" will be applied to all dependencies, and so on. — Alex Cohn

Alex Cohn Alex Cohn · Accepted Answer · 2012-10-29T21:57:38

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.

How to compile two different libraries in same Android.mk linking one of them to other

2 Answers