Develop Reference

Android.mk Build problem with sub directories

I had trouble with Android.mk in PROJECT_FOLDER directory,
//Android.mk
LOCAL_PATH:= $(call my-dir)
include $(call all-makefiles-under,$(LOCAL_PATH))
and in PROJECT_FOLDER, say there were SUB_DIR1 and SUB_DIR2
in SUB_DIR1, I had Android.mk file, but in SUB_DIR2 I did not.
And I've found out that build system doesn't go through SUB_DIR2 but SUB_DIR1,
but I am not sure why.
My guess is that my Android mk goes through every sub directory under Android.mk, searching for another Android.mk or Android.bp,
and if one directory does not have Android.mk at top, it just assumes that the directory is unrelevant?
could anyone enlighten me?

Replacing some files before packaging system folder to system.img

As the title is self-explanatory, I'd want to replace some files in system/bin/ and system/lib/ right before when the system.img is being generated.
To be more exact, I've got some prebuilt .so files which shuold be copied over the existing ones. For example libart.so. Please note that replacing art/ (source code of art) with the modified art source code is not an option.
To do this, which mk file should I investigate and put my replacing code into?

You may follow the same structure as the one proposed in this other question, but use this macro:
PRODUCT_COPY_FILES += \
device/common/my_bin.bin:cache/my_bin.bin \
device/common/my_so.so:system/art/my_so.so
This works as follows:
The file is copied from left to(:) right.
When the image is generated, in this case cache or system, it would be generated with the files contained in those folders.
As we have copied our files to that destination, when system.img is generated, our file will be contained.
Also, the order in which this files are copied, matters. For instance if you are copying a file that already exists, hence, you want it replaced. (As your libart.so), you would need YOUR call to that copy to be done before the default one.
For this, I recommend doing:
source build/envsetup.sh
lunch <<device>>
mgrep libart.so -> This does a grep through mk files, so you can see where the default copy is done.
Insert $(info whatever) calls in desired mk files to trace where is a good spot to add your PRODUCT_COPY_FILES.
It's not easy to answer where to add it. I have never modified libart.so myself, but I have copied many files this way and it works like a charm.
I hope it works for your case as well.

A quick dirty way to this:
Copy desired files to out(..)/system/lib or wherever after system.img has been built
make snod
Other way is using Android.mk. Create a new dir in device tree eg libart-prebuilt. Put here your lib, then create an Android.mk file with content
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := libart-prebuilt
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE_PATH := $(TARGET_OUT)/lib
LOCAL_MODULE_STEM := libart
LOCAL_MODULE_SUFFIX := $(TARGET_SHLIB_SUFFIX)
LOCAL_SRC_FILES := libart.so
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
include $(BUILD_PREBUILT)
Now just add libart-prebuilt to PRODUCT_PACKAGES in your device.mk

Also there's an option to add binary .so library as a product package, using PREBUILT_SHARED_LIBRARY option in .mk file: Include prebuilt shared library in Android AOSP or BUILD_PREBUILT https://stackoverflow.com/a/25682674/1028256

Android Copy directory tree recursively using make files

I need to copy a directory tree with XML files recursively to the out directory using Android.mk file
The directory structure is like this:
parent directory has three sub-directories each with an XML file. The parent directory also includes an Android.mk file.
The Android.mk file in parent has the following rules:
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := file.xml
LOCAL_MODULE_TAGS := optional debug
LOCAL_MODULE_CLASS := ETC
LOCAL_MODULE_PATH := $(TARGET_OUT_ETC)
LOCAL_SRC_FILES := file.xml
include $(BUILD_PREBUILT)
I need to define LOCAL_SRC_FILES and LOCAL_MODULE_PATH as the source and target directories.
Could someone please let me know how to do it?

Basically the issue here is the "LOCAL_MODULE" needs to be defined for each file in this case. And it needs to be unique. If we try to have the same name for all three subdirectories, make fails with an 'already defined' error.
As a workaround, I defined LOCAL_MODULE for each of the three files with unique filenames. I don't think there is any other option of resolving this.
As an aside, I ought to mention that it is possible to copy files by running cp command directly from make. Please see Copy multiple txt files in /system using Android.mk
However, please note that running shell commands directly from within Android.mk files is deprecated starting from Android N.

Newbie in Android NDK: definition in Android.mk

I am new in Android NDK. I know in every jni/ folder, there is Android.mk file, seems it always start with:
LOCAL_PATH := $(call my-dir)
It defines the LOCAL_PATH, but if translate it to a human-readable launguage, what is this path? Is the LOCAL_PATH points to the jni/ folder or is it the project root ?
For example, I imported an Android project which uses NDK, I checked its Android.mk file, it has something like following:
LOCAL_PATH := $(call my-dir)
...
MY_PLUGINS := XXX YYY ZZZ
MY_PATH := $(LOCAL_PATH)/other/something
Question 1, what does LOCAL_PATH := $(call my-dir) mean, what is the path it points to?
Question 2, Where can I find those MY_PLUGINS, I mean the XXX , YYY and ZZZ, at least I am not able to see it in the project I imported.
Question 3, Where can I find something defined by MYPATH ? I don't see it in project either.
P.S.: (I tried to find it under jni/other/something , but there isn't such file). By the way, what is the name of the script language used in Android.mk ?

Your best resource here is probably the NDK documentation itself. It is (unfortunately) not hosted on the web, but it is distributed with the NDK. Check the android-ndk-rX/documentation.html file in the NDK you downloaded.
Question 1: from the Android.mk File part of the doc:
LOCAL_PATH := $(call my-dir)
An Android.mk file must begin with the definition of the LOCAL_PATH variable. It is used to locate source files in the development tree. In this example, the macro function 'my-dir', provided by the build system, is used to return the path of the current directory (i.e. the directory containing the Android.mk file itself).
Question 2 and 3: these variables are not "usual" variables in an Android.mk file. They are user-defined variables, and without more details on the project you're using, it's hard to tell much about it. For all I know, MY_PATH should indeed point to jni/other/something.
Concerning your P.S., I don't think the Android.mk file is written in any particular known language: it's a custom language that has some similarities with Makefile.
Hope this helps a little!

Q - 1
Android.mk file must begin with LOCAL_PATH variable initialization.
LOCAL_PATH contains the "path to the Android.mk make file", in most case it would be present working directory.
$(call my-dir) is calling macro function "my-dir", defined in /build/core/definitions.mk, you can check the definition of the macro, It finds the directory for ndk-build script to start working.
Q - 2
Android.mk allows users to define local variables and "MY_PLUGINS" is a local variable containing list of plugins, "XXX YYY ZZZ" is list of the plugins he/she might be using within the Android.mk file.
Following are the restrictions on defining a local variable
Names that begin with LOCAL_ (e.g. LOCAL_MODULE)
Names that begin with PRIVATE_, NDK_ or APP_ (used internally)
Lower-case names (used internally, e.g. my-dir)
It is advised to use MY_ prefix for local variable definition
Q - 3
Again MY_PATH is a local variable which contains absolute path to the "/something/other" folder, now this path could contain "XXX YYY ZZZ" plugins or some other useful stuff.
Hope this helps

How can I specify a file to be copied in an Android.mk file

Is there a macro or command to copy files? I'd like a 3rd party library (libThirdParty.so) to be copied to the output directory (lib). This is the contents of my Android.mk file
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := ndkFoo
LOCAL_SRC_FILES := ndkFoo.c
LOCAL_LDLIBS := -L$(SYSROOT)/usr/lib -llog
include $(BUILD_SHARED_LIBRARY)

I have a build step I added for one of my .cpp files that's generated; you could do something similar.
Note that I was told that what I was doing was Not Supported by Google, so use at your own risk. I've been using something like the code below for more than a year, though. Here's a rough idea of what it would look like:
LOCAL_PATH:= $(call my-dir)
# this was important for some cases; can't remember if it's important here, but I don't want to steer you wrong if it isn't
REAL_LOCAL_PATH:=$(LOCAL_PATH)
include $(CLEAR_VARS)
LOCAL_MODULE := ndkFoo
# again, I'm being paranoid here
REAL_LOCAL_MODULE := $(LOCAL_MODULE)
LOCAL_SRC_FILES := ndkFoo.c
$(REAL_LOCAL_PATH)/obj/local/armeabi/$(REAL_LOCAL_MODULE).so : $(REAL_LOCAL_PATH)/libs/armeabi/libThirdParty.so
$(REAL_LOCAL_PATH)/libs/armeabi/libThirdParty.so : $(PATH_TO_LIB_THIRD_PARTY)/libThirdParty.so
cp $(PATH_TO_LIB_THIRD_PARTY)/libThirdParty.so $(REAL_LOCAL_PATH)/libs/armeabi/libThirdParty.so
LOCAL_LDLIBS := -L$(SYSROOT)/usr/lib -llog
include $(BUILD_SHARED_LIBRARY)
Note you'll need to define PATH_TO_LIB_THIRD_PARTY.
ALSO note that copy-and-paste may or may not work. Makefiles are notoriously picky about indents. I'd make sure that the "cp" line has a real tab indent, and that nothing else is indented. If "cp" doesn't work, then make may be delegating to CMD, and you can try "copy" instead.
Good luck.

I know this thread is old, but found it while searching for something myself.
From the PowerVR SDK, Android.mk file.
You can create folders and copy files.
PVRSDKDIR := $(LOCAL_PATH)
ASSETDIR := $(PVRSDKDIR)/TrainingCourse/IntroducingPOD/OGLES2/Build/Android/assets
$(ASSETDIR):
-mkdir $(ASSETDIR)
$(ASSETDIR)/tex_base.pvr: $(ASSETDIR) $(PVRSDKDIR)/TrainingCourse/IntroducingPOD/OGLES2/tex_base.pvr
cp "$(PVRSDKDIR)/TrainingCourse/IntroducingPOD/OGLES2/tex_base.pvr" "$(ASSETDIR)/"

Google has a feature that is exactly intended for your use case: PREBUILT_SHARED_LIBRARY
If you check the documentation in the docs directory included in the NDK, you will find ANDROID-MK.html which mentions this feature briefly, and PREBUILTS.html which completely documents the feature. You can specify the source and destination directories, and you can specify a new name for the file when it is copied.
There is also PREBUILD_STATIC_LIBRARY which does the same thing for a static library.
It might be possible to trick it into copying arbitrary files... the above features are implemented by files called, respectively, prebuilt-shared-library.mk and prebuilt-static-library.mk. Inside, they define an extension that must be on the file (respectively .so and .a). You could probably make another .mk file that defined some other extension to enable copying some other kind of file. But we have only needed to copy libraries and we haven't experimented with trying to trick the build system.
P.S. This blog posting is interesting. It refers to BUILD_PREBUILT, which doesn't exist in my copy of the NDK. I wonder if this blog posting refers to an earlier version of the NDK, which had BUILD_PREBUILT to copy any kind of file (with no check for a required extension).
http://karthiksden.blogspot.com/2011/03/copying-data-files-using-androidmk.html