Reputation: 163
I want to build an shared library. To build it, I need to call another shared library. Here is what I did:
1.Create one Android project,named "BuildLib",and add a new folder "jni" under the project directory. Contents of jni folder:
jni-->Android.mk
-->Application.mk
-->add.cpp
-->add.h add.cpp just do two numbers addition:
add.h:
int add(int a,int b);
add.cpp:
#include "add.h" int add(int a,int b){ return a+b;}
Android.mk:
LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) LOCAL_SRC_FILES := add.cpp LOCAL_MODULE := add include $(BUILD_SHARED_LIBRARY)
After build the project,I got libadd.so under directory $(BUILDLIB)/libs/armeabi/
.
Create another Android project, named "CallLib". Copy libadd.so
and add.h
to jni folder, create Android.mk
, Application.mk
, and call_add.cpp
.
Android.mk:
LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) LOCAL_SRC_FILES := libadd.so LOCAL_MODULE := add_prebuilt include $(PREBUILD_SHARED_LIBRARY) include $(CLEAR_VARS) LOCAL_C_INCLUDES := $(LOCAL_PATH) LOCAL_SRC_FILES := call_add.cpp LOCAL_MODULE := native LOCAL_SHARED_LIBRARIES := add_prebuilt include $(BUILD_SHARED_LIBRARY)
call_add.cpp:
#include "add.h" int call_add(){return add(1,2);}
After all above, I build the CallLib project, but got the error:
undefined reference to 'add(int, int)';
I think the libadd.so
can not be found, but I don't know how to modify. Does anyone know how I can fix this? Any help will be appreciated.
Upvotes: 16
Views: 21118
Reputation: 16852
Just in case anyone needs it:
A bit hackish way to keep the linker happy:
LOCAL_LDLIBS := -llog
or
LOCAL_LDLIBS := -L$(LOCAL_PATH)/lib -lMyStuff
Less hackish:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := xyz
LOCAL_SRC_FILES += xyz/xyz.c
LOCAL_LDLIBS := -llog
include $(BUILD_SHARED_LIBRARY) # this builds libxyz.so
include $(CLEAR_VARS)
LOCAL_MODULE := abc
LOCAL_SHARED_LIBRARIES := xyz # <=== !!! this makes libabc.so dependent on libxyz.so
LOCAL_SRC_FILES := abc/abc.c
#LOCAL_LDLIBS := ...
include $(BUILD_SHARED_LIBRARY) # this builds libabc.so
Upvotes: 1
Reputation: 4941
In your second Android.mk
, try replacing the first module with:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_SRC_FILES := libadd.so
LOCAL_MODULE := add_prebuilt
LOCAL_EXPORT_C_INCLUDES := add.h
include $(PREBUILD_SHARED_LIBRARY)
The LOCAL_EXPORT_C_INCLUDES
flag should attach the header information to the add_prebuilt
module, so it can be linked with your final library.
Upvotes: 4