Develop Reference

How to include util-linux in AOSP?

How do I include util-linux from here in AOSP? Where should I add this util-linux folder in AOSP so that I can build AOSP and these utils could be added in /system/bin/ or /system/xbin/? And is there any specific Makefile or Android.mk that I need to make it to compile with Android build?

I have added an application from util-linux package in AOSP.
Here's how I did it. I added the util-linux (2.34) from https://mirrors.edge.kernel.org/pub/linux/utils/util-linux/v2.34/util-linux-2.34.tar.gz in external of AOSP folder.
I just wanted to add chrt from util-linux. Therefore, I run the normal make command in util-linux to see what files are compiled for chrt. I took a note and created an Android.mk accordingly. I am sure there's a better way to do it hierarchically by making the library first and then make the chrt executable. However, this works too.
I added the following Android.mk at external\util-linux\. The Android.mk looks like the following:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := sohamchrt
LOCAL_SRC_FILES := schedutils/chrt.c lib/blkdev.c lib/canonicalize.c \
lib/crc32.c lib/crc32c.c lib/idcache.c lib/fileutils.c \
lib/ismounted.c lib/color-names.c lib/mangle.c lib/match.c lib/mbsalign.c \
lib/mbsedit.c lib/md5.c lib/pager.c lib/parse-date.c lib/pwdutils.c lib/randutils.c \
lib/setproctitle.c lib/strutils.c lib/timeutils.c lib/ttyutils.c lib/exec_shell.c \
lib/strv.c lib/sha1.c lib/signames.c lib/linux_version.c lib/loopdev.c \
lib/plymouth-ctrl.c lib/cpuset.c lib/path.c lib/procutils.c lib/sysfs.c
LOCAL_CFLAGS = -DHAVE_NANOSLEEP -include config.h \
-isystem bionic/libc/upstream-openbsd/android/include
LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
include $(BUILD_EXECUTABLE)
Now, when I run m -j8 iso_img, then Android tries to compile sohamchrt. I named the package sohamchrt because chrt is already provided by toybox which have limitations.
The problem is util-linux is not fully compatible with bionic. So, I needed to make some changes to some .c and .h files such as fileutils.c, include/c.h, etc.
After successful compilation, the binary sohamchrt appears in /system/bin when Android is running, and it works with no issues.
This is also a guide on how you can add a C source file for a userspace executable binary in AOSP.

It's always worth checking whether a library you want to add already exists at https://android.googlesource.com/. In your case, unfortunately, it does not.
As util-linux does not come with an Android.bp. You will have to understand how util-linux is built and how Soong works to create a custom Android.bp for integration. The correct folder to place it would be external/util-linux/.
Maybe you will want to take a shortcut and just add util-linux as prebuilt binaries. That will reduce the effort.
Please check licensing issues first, though.

Why isn't libgnustl_shared.so being copied from my APK?

I have an android project with a libs folder structure like this:
/libs
/armeabi
libfoo.so
libbar.so
libmystuff.so
libgnustl_shared.so
/armeabi-v7a
libfoo.so
libbar.so
foo and bar are third party libraries, mystuff is my own library from a separate android JNI project which requires gnustl_shared, which is from the same JNI project.
When I build my project in Eclipse, I can view the contents of the generated APK using unzip -l, and it indeed shows that all of these library files have been included.
However, after installing the APK, the /data/data/com.myproject/lib folder contains no libgnustl_shared.so, even though the other libraries are present.
This inevitably leads to the following error:
UnsatisfiedLinkError: Couldn't load gnustl_shared: findLibrary returned null
As a sanity check, I ran adb push ./libs/armeabi/libgnustl_shared.so /data/data/com.myproject/lib and sure enough, the application starts as expected.
I don't see anything in the build log or Eclipse console that suggests there were any issues building or installing the app.
What could be preventing libgnustl_shared.so from being installed with my application?
Where can I go to learn about what happens when an APK is installed?
Please let me know in a comment if there's any specific information I can provide that might help.

I think that, in your JNI project's Android.mk file, most probably, when you build libmystuff.so, you're referencing libgnustl_shared.so like:
LOCAL_LDLIBS += -lgnustl_shared
Maybe you can try to add it as a module (NDK works really focused on modules), something like:
include $(CLEAR_VARS)
LOCAL_MODULE := gnustl_shared
LOCAL_SRC_FILES := libgnustl_shared.so
include $(PREBUILT_SHARED_LIBRARY)
and (in the section you're building libmystuff.so):
LOCAL_SHARED_LIBRARIES := gnustl_shared
And check if it's finally copied

I think your libgnustl_shared.so need under /armeabi-v7a not under /armeabi
Please try copy libgnustl_shared.so to /armeabi-v7a

Look at the answer here: How to link any library in ndk application
The problem is most likely in your Android.mk file. You should have a line like the one on the bottom:
include $(BUILD_SHARED_LIBRARY)
If not, then you're not including your shared library.

OpenCV Android NDK Project will not build

I am using OpenCV 2.4.4 with Eclipse Juno on Ubuntu.
My problem is similar to this one OpenCV for android sample programs showing error
But is now weirding me out. I spent most of my weekend trying to get the ndk and opencv library to play nice and still I cannot get it to work. I have in my test C++ cpp file with the following includes -
#include <jni.h>
#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <cstdlib>
using namespace cv; //this is a problem
...
...
And it tells me when I try to build that "namespace cv cannot be found".
Oh well, I must have written some path wrong or am not using the correct library, right?
Wrong.
In the terminal, ndk-build builds the .so files without any errors. I can see them plain as day in the project folder.
But if I try to do build in eclipse, i.e. build the apk for tesitng on a virtual device or real device, then I get the namespace cv error and the build fails and then in the cpp file cv is underlined red and in eclipse the file is marked red and I can't even attempt to build until this file is "corrected".
Clearly I'm doing something wrong. But if I close my eclipse project and then reopen it, the cpp file is no longer marked red and I can make an apk build. If I attempt to open the cpp file the red returns and no more builds can happen until I go through the project close/open rigmarole.
I honestly don't know what the cause of the problem is. Any help would be greatly appreciated.
My android.mk file:
include $(CLEAR_VARS)
OPENCV_CAMERA_MODULES:=off
OPENCV_INSTALL_MODULES:=on
OPENCV_LIB_TYPE:=STATIC
include /the/correct/path/tp/opencv/sdk/native/jni/OpenCV.mk
LOCAL_MODULE := mylib
LOCAL_SRC_FILES := mylib.cpp
include $(BUILD_SHARED_LIBRARY)
Application.mk
APP_STL := gnustl_static
APP_CPPFLAGS := -frtti -fexceptions
APP_ABI := all #i have tried various targets
APP_PLATFORM := android-8
APP_MODULES := mylib
I didn't think it would be this difficult. I should add that I have successfully used opencv with Android in anothe rproject I built on WIndows with Eclipse 3.5 (I think) and OpenCV 2.4.2
EDIT
I also want to say that I just did a quick 'n dirty test opencv operation. I wrote a quick Sobel function and called it as a native function in a Java file and "sobelled" a bitmap successfully. Of course, I still had to close/open my project to do this.

Hi I had same problem with you and after I added below "opencv android sdk" path that include problem disappeared.
exp : C:\project\OpenCV-2.4.6-android-sdk\sdk\native\jni\include
switch the path with your opencv-android-sdk path.

I know that's maybe too late, but in my case (Windows+Eclipse) I correct this problem just changing the backslash "\" to slash "/" in the Path and Symbols include of opencv jni libs.
Example:
Wrong H:\opencv\sdk\native\jni\include
Correct H:/opencv/sdk/native/jni/include

Linker trouble when using LuaJIT prebuilt static library with android under cygwin

I think I spent most of yesterday unsuccessfully wrestling with this, any help would greatly appreciated and make me extremely happy! Even a next step to try to find the root of the issue is something I'm stuck on at the moment!
I have an Android 2.2 project that's trying to reference a prebuilt LuaJIT static library but ndk-build gives me this error:
test_android.cpp:25: undefined reference to `luaL_newstate'
I built LuaJIT as liblua.a, I've placed that in the root of my JNI directory with the relevant headers. I've have one Android.mk as shown below:
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := lua
LOCAL_SRC_FILES := liblua.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := test
LOCAL_CFLAGS := -Werror
LOCAL_SRC_FILES := test_android.cpp
LOCAL_LDLIBS := -llog -lGLESv2
LOCAL_STATIC_LIBRARIES := lua
include $(BUILD_SHARED_LIBRARY)
In test_andrdoid.cpp I've got this code:
extern "C"
{
#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"
}
void test()
{
lua_State* lua = lua_open();
}
This seems like a linker error, for some reason the static library file is not being correctly referenced. But, to me, the makefile seems correct.
Any help would be greatly appreciated!
To start with: is there anyway to see how everything is being linked
together and if my shared library module is really get access
to the static library?
Additional Information
Here's extra information that I think could be relevant!
Building the library
Maybe it's the static lib file that's not correct? (Is there anywhere I could download a prebuilt one to check?). I made it with this script (from the LuaJIT website). I'm using the latest stable LuaJIT, 1.1.8
NDK=/cygdrive/c/android-ndk-r8b
NDKABI=8
NDKVER=$NDK/toolchains/arm-linux-androideabi-4.4.3
NDKP=$NDKVER/prebuilt/linux-x86/bin/arm-linux-androideabi-
NDKF="--sysroot $NDK/platforms/android-$NDKABI/arch-arm"
make linux HOST_CC="gcc -m32" CROSS=$NDKP TARGET_FLAGS="$NDKF"
This builds fine and creates a liblua.a in the /src/ directory. (I ran nm on it and it lists out all the function prototypes I'd expect). I don't know if there's anything else I can do to ensure it's really a build for ARM?
NDKABI=8 means I'm targeting Android 2.2
Setting up the test Android Project
I create a brand new 2.2 android project using this command:
android create project --target 3 --name test --path . --activity TestActivity --package com.test
Target 3 maps to Android 2.2 on my system (using android list devices).
I create the jni folder and have a test_android.h and test_android.cpp. Then I use ndk-build to build them - which works fine when I'm not trying to reference LuaJIT. When I do try and use Lua I get the following error:
Full Error Message
Cygwin : Generating dependency file converter script
Compile++ thumb : test <= test_android.cpp
In file included from jni/test_android.h:3:0, from jni/test_android.cpp:2:
C:/android-ndk-r8b/platforms/android-8/arch-arm/usr/include/jni.h:592:13: note:
the mangling of 'va_list' has changed in GCC 4.4
Prebuilt : liblua.a <= jni/
StaticLibrary : libstdc++.a
SharedLibrary : libtest.so
obj/local/armeabi/objs/test/test_android.o: In function `test()':
C:\Users\Grrr\Documents\mycode\static_lib_test/jni/test_android.cpp:25: undefined reference to `luaL_newstate'
collect2: ld returned 1 exit status
/cygdrive/c/android-ndk-r8b/build/core/build-binary.mk:378: recipe for target `obj/local/armeabi/libtest.so' failed make: *** [obj/local/armeabi/libtest.so] Error 1
Most of the issues I've seen searching around are due to the local library include order, as I only have one library this shouldn't be an issue and suggests I've managed to get something more fundamental wrong :)
Update
I've since built normal Lua and added that as prebuilt static library and it works fine. I suspect its how I've built LuaJIT but I'm not sure how to correctly build it, or find a working prebuilt version.

The linking for this was fine, or at least the makefile was.
The problem was the LuaJIT library wasn't built for ARM (I used objdump -a lualib.a, to check this). I downloaded the latest LuaJIT, ran the script under linux and got an ARM library. Everything links nicely now!

Android-NDK build system (building hello-gl2)

I downloaded and installed Android-NDK on my Archlinux, using this package.
Got no issues building (and running) the sample hello-jni following the guide on this page, but if I try to do the same with hello-gl2 I get some errors; it looks like it cannot find some header files:
$ ../../ndk-build
/usr/bin/make -f /opt/android-ndk/build/core/build-local.mk
Compile++ thumb : gl2jni <= gl_code.cpp
/opt/android-ndk/samples/hello-gl2/jni/gl_code.cpp:22:23: error: GLES2/gl2.h: No such file or directory
/opt/android-ndk/samples/hello-gl2/jni/gl_code.cpp:23:26: error: GLES2/gl2ext.h: No such file or directory
--- SNIP ---
GLES2/gl2.h and GLES2/gl2ext.h are however present in $(NDK)/platforms/android-4/arch-arm/usr/include/, and it looks like$(NDK)/build/core/setup-toolchain.mk should set such include path.
Has anybody encountered the same issue? How can I compile this sample?
And then, are there other options to easily build Android-NDK applications? This build system seems quite complicated to me, and I'd prefer using cmake to build my applications.

make sure that APP_ABI and APP_PLATFORM is defined in your Application.mk and your APP_PLATFORM should be higher than android-5... check: gl.h & glext.h not found
for example, in Application.mk define:
APP_ABI := armeabi #armeabi-v7a
APP_STL := stlport_static
APP_PLATFORM := android-8

In my case it was missing the file default.properties with such content:
target=android-5
Put this file into the root project directory. It may help.

You need to use a higher SDK. Level 5 is the minimum to build OpenGL ES 2 code.