$(LOCAL_PATH) not returning the path to current directory correctly

Issue

I am using Android NDK to compile a shared library. I am using the latest build of Android Studio (Android Studio 15- #AI-141.2422023 ). In my cpp code, I am using a thirdparty shared library. When writing the Android.mk file, I have first created a PREBUILT_SHARED_LIBRARY with the following code.

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := essentia
LOCAL_SRC_FILES := $(LOCAL_PATH)/../../../essentia-shared/lib/libessentia.so
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/../../../essentia-shared/include/essentia

include $(PREBUILT_SHARED_LIBRARY)

The problem I am facing is that $(LOCAL_PATH) is behaving a bit weirdly. The path it is returning is

 jni/jni/../../../essentia-shared/lib/libessentia.so

I have the following questions:

1. I am not sure, why there are two jni's appended at the front of the path. Also when I tried to print the value of LOCAL_PATH by using $(warning $(LOCAL_PATH)), it prints jni.
2. Shouldn't $(LOCAL_PATH) return the absolute path? This is even more confusing because at times I got the absolute path using $(LOCAL_PATH).

PS: I am using the terminal internal to Android Studio to run ndk-build

Edit 1: I run the ndk-build from src/main

Solution

$(call my-dir) from src/main for src/main/jni/Android.mk results in "jni". On the other hand, LOCAL_SRC_FILES are always treated relative to the LOCAL_PATH, which is "jni". That's how jni/jni appears for your .so.

On the other hand, all …_INCLUDES are treated relative to working directory, which in your case is src/main from where you launched ndk-build. Due to the delicate nature of current directory, it is a good practice to use absolute paths for all include paths.

So, this is the suggested rewrite of this part of your Android.mk:

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := app-lib
LOCAL_SRC_FILES := a.cpp b.cpp
LOCAL_SHARED_LIBRARIES := essentia
include $(BUILD_SHARED_LIBRARY)

LOCAL_PATH += /../../../essentia-shared
include $(CLEAR_VARS)
LOCAL_MODULE := essentia
LOCAL_SRC_FILES := lib/libessentia.so
LOCAL_EXPORT_C_INCLUDES := $(abspath $(LOCAL_PATH)/include/essentia)
include $(PREBUILT_SHARED_LIBRARY)

Answered By - Alex Cohn