How to build library with the same MODULE name for different ABI from different source file in ndk?

in ndk, I want to build library with the same MODULE name for different ABI from different source file.

I have two sources under dir: armeabi-v7a and arm64-v8a

Here is my Android.mk:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := session
LOCAL_SRC_FILES := armeabi-v7a/libsession.so
TARGET_ARCH_ABI := armeabi-v7a
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := session
LOCAL_SRC_FILES := arm64-v8a/libsession.so
TARGET_ARCH_ABI := arm64-v8a
include $(PREBUILT_SHARED_LIBRARY)

Here is my Application.mk:

APP_STL := gnustl_static
APP_CPPFLAGS := -frtti -fexceptions
APP_ABI := armeabi-v7a arm64-v8a
APP_PLATFORM := android-21

but failes:
Android NDK: Trying to define local module 'session' in jni/Android.mk.
Android NDK: But this module was already defined by jni/Android.mk.

How to achieve that?

Solution

The simplest way would be to use the fact that your .so file appear to be located in subdirectories named after the ABI:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := session
LOCAL_SRC_FILES := $(TARGET_ARCH_ABI)/libsession.so
include $(PREBUILT_SHARED_LIBRARY)

If that hadn't been the case you could've checked the value of TARGET_ARCH_ABI and acted accordingly. For example:

ifeq ($(TARGET_ARCH_ABI),armeabi-v7a)
LOCAL_SRC_FILES := foo/libfoo.so
else ifeq ($(TARGET_ARCH_ABI),arm64-v8a)
LOCAL_SRC_FILES := bar/libbar.so
endif

There's no need to set TARGET_ARCH_ABI yourself - it's set for you by the build system.