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Native library not found on android build?

I am getting this error: unable to lookup library path for, native render plugin support disabled when I run my app on android. I think I am building the shared libraries incorrectly.
I am looking to build the source files from this repo. I'll say my build process and perhaps someone can spot a step I'm missing or doing incorrect.
Following this guide, I came up with this:
Android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := libhydrogen
LOCAL_SRC_FILES := ..\hydrogen.c
include $(BUILD_SHARED_LIBRARY)
Application.mk
APP_PLATFORM := android-16
APP_OPTIM := release
APP_MODULES := libhydrogen
Next I:
Placed these files in the jni folder.
Called ndk-build.
Copied the .so files from the \libs folder and placed them in their respective folders in Unity (i.e. Hydrogen\Plugins\Android\arm64-v8a).
Made sure their platforms and CPU architectures were correct.
Built my app.
Here is the c# wrapper I am using.
Calling Hydrogen.Library.Initialize(); is then giving me this error.
Here is the full logcat related to this error.
And in the case my build process manages to be correct, and the .so files are fine; what else might cause this to happen?
Edit: I am trying to build for armeabi-v7a and `x86. Here are the .so file details, maybe there is something there that is not right? I am unfamiliar with c and since I haven't heard of anyone building this library for android, I wonder: could there be anything within the c source file that is incompatible with the NDK build process?

Native libraries are loaded by the native linker of the system, in your case, the linux dynamic linker: ld.so (it changes names sometimes, so I used that name, as you can check the man page in the documentation with that name).
For that to happen, in general, you need to provide a LD_LIBRARY_PATH environment variable to the java virtual machine, so it can effectively dlopen(3) it.
Think how different can be your development system to your target one.... and you'll easily get to that.

It was a bug with Unity! For some reason when switching the project's target platform some of my files would get corrupted. Strangely, it only seems to happen in this one project, but in any case the (temporary) solution is to re-import the plugin folder whenever I switch platforms.

Hello-Jni on Windows, Android NDK - build-local.mk: No such file

I have tried scouring the Internet and StackOverflow (too many articles to count) but cannot find assistance that is all of these things:
More recent than 2013
Does not require Cygwin if developing
on Windows
Is geared to Android Studio, NOT Eclipse.
I am diving head first into Android development for the very first time and the project I have newly joined depends on developing with the NDK. I've been reading the docs that come with the NDK but have run into a stone wall with this sample.
I am trying to build hello-jni, the sample project within the NDK. Here is my environment:
Android Studio 1.4 (most up to date, stable version currently available)
NDK version: r10e
OS: Windows 7
Contents of Application.mk file:
APP_ABI := all64 // Came with 'all', read somewhere on SO that it
// should be 'all64'. Result is the same.
Contents of Android.mk file:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := hello-jni
LOCAL_SRC_FILES := hello-jni.c
include $(BUILD_SHARED_LIBRARY)
My PATH environment variable includes a path to my NDK root folder and to \prebuilt\windows-x86_64\bin (because I read on one of many articles that it should.) When I navigate to the hello-jni root folder though, and call ndk-build, I am only presented with errors.
c:\NDK\android-ndk-r10e\build\core\build-local.mk:40: c:/NDK/android-ndk-r10e/build/core/build/core/init.mk: No such file or directory
c:\NDK\android-ndk-r10e\build\core\build-local.mk:191: \add-application.mk: No such file or directory
c:\NDK\android-ndk-r10e\build\core\build-local.mk:206: \setup-imports.mk: No such file or directory
c:\NDK\android-ndk-r10e\build\core\build-local.mk:223: \build-all.mk: No such file or directory
make.exe: *** No rule to make target `\build-all.mk'. Stop.
If anything else is required for people to assist me, say the word I will provide what I can. All help will be greatly appreciated.
EDIT:
Most of the articles of I've seen for Windows mention Cygwin, but according to the docs, it isn't needed. If this is incorrect, please correct me?
Except from \android-ndk-r10e\docs\Programmers_Guide\html\md_3__key__topics__building__s_t_a_n_d_a_l_o_n_e-_t_o_o_l_c_h_a_i_n.html
Windows support
The Windows binaries do not depend on Cygwin. The good news is that they are thus faster, the bad news is that they do not understand the Cygwin path specification like /cygdrive/c/foo/bar (instead of C:/foo/bar).
The NDK build system ensures that all paths passed to the compiler from Cygwin are automatically translated, and deals with other horrors for you. If you have a custom build system, you may need to deal with the problem yourself.

I can't take the credit for this answer, a coworker kindly sleuthed it out for me. When he found the answer, I demanded to know what else he had done, because clearly I must have missed some magic? I only saw him switch two lines in a make file, there had to be more? Alas, no. This alone was the source of my woe.
While I'm hesitant to call it an error within the NDK because I don't know how it works with Cygwin, neither of us can understand how this has ever worked for anyone building in native Windows, as the line I will be referencing is recorded in the git repository as being added back in 2011 or 2010. ( https://android.googlesource.com/platform/ndk/+/master/build/core/build-local.mk )
To aid explanation, here is the first line of my error again:
c:\NDK\android-ndk-r10e\build\core\build-local.mk:40: c:/NDK/android-ndk-r10e/build/core/build/core/init.mk: No such file or directory
The first file that is unable to found is ...build/core/build/core/init.mk, which of course doesn't exist because build/core should not be repeated.
The command that begins the build, ndk-build.cmd, calls build\core\build-local.mk to begin the process. Inside this file the environment variable, NDK_ROOT, is recreated upon entry. Whatever my NDK_ROOT is, is irrelevant.
NDK_ROOT := $(dir $(lastword $(MAKEFILE_LIST)))
NDK_ROOT := $(strip $(NDK_ROOT:%build/core/=%))
NDK_ROOT := $(subst \,/,$(NDK_ROOT))
NDK_ROOT := $(NDK_ROOT:%/=%)
.
.
.
The second line strips the end of the current directory (the build/core/) from the end of my new NDK_ROOT, because the true root should be the parent directory of build and because it will be added back later to find all those 'missing' files. That's fine, except note the forward-slashes (/) used in the search. Windows does not use (or in my experience at least, usually does not return) forward-slashes, though it will often parse them if that is what it's given. (When changing directories, for example, I've found either to be acceptable as long as I already know where I need to go. Tab completion does not seem to function if my path ends with a /.)
Oh, but look at the third line (added way back in 2011)! A substitution is made of every backslash (\) in NDK_ROOT, replaced with forward-slash (/). So the replacement of build/core/ should go off without a hitch, right? Problem: it's too late.
The strip call has already occurred and if the NDK_ROOT received a path with backslashes instead of forward-slashes, build/core/ is never found and stripped from the variable. How did my coworker fix it? Easy. He switched the lines around:
NDK_ROOT := $(dir $(lastword $(MAKEFILE_LIST)))
NDK_ROOT := $(subst \,/,$(NDK_ROOT))
NDK_ROOT := $(strip $(NDK_ROOT:%build/core/=%))
NDK_ROOT := $(NDK_ROOT:%/=%)
My hello-jni project now builds, along with Teapot, another sample from the NDK, which I tried just to be sure. And so does native-audio, native-codec, native-media, and More Teapots. Haven't tried to run them yet... but I have no build errors.
I don't know if this fix will break Cygwin users, I don't have that on my box. I also don't know if it would break Linux environments because I don't have Linux on my box. But this may help native Windows users, and I hope so, because I uselessly beat my head on this for 3 or 4 days and read more SO articles than I ever care to at once.

Using a windows machine I encountered this error but it was saying the clear-vars.mk : No such file or directory. After I looked at the ndk-build.cmd in the directory
C:\Users\\AppData\Local\Android\Sdk\ndk-bundle\build
the file looks like this
#echo off
set NDK_ROOT=%~dp0\..
set PREBUILT_PATH=%NDK_ROOT%\prebuilt\windows-x86_64
if exist %PREBUILT_PATH% goto FOUND
set PREBUILT_PATH=%NDK_ROOT%\prebuilt\windows
:FOUND
"%PREBUILT_PATH%\bin\make.exe" -f "%NDK_ROOT%\build\core\build-local.mk" SHELL=cmd %*
But you will also find the same file name under directory
C:\Users\jmatthews\AppData\Local\Android\Sdk\ndk-bundle
and the file looks like this
#echo off
%~dp0\build\ndk-build.cmd %*
remove the second line so it looks like this with only 1 line echo off
#echo off
This file is called and messes up the Windows directory structure. After that I was able to compile on windows. Also I had issues with the project using a space in the directory so move your project location to directories without spaces.

Adding prebuilt set of files structured in folders to android out folder

I have glibc compiled for arm which is different from Android glibc or the bionic C as the glibc environment I have complied will help in providing more api's.
Now I can copy the glibc environment on /system/ folder while Android is running, and on doing chroot I can run my programs on glibc environment.
Currently I am compiling glibc and Android separately and then tarring the glibc and copying it on Android emulator sdcard and then untarring it on /system folder and then doing chroot on /system/glibc
I compile glibc separately and then place it somewhere in Android source code.
Now while compiling Android source, what should I do so that the entire prebuilt folder structure of glibc gets copied to /system folder and become part of part of system.img.
With this when I copy the system.img to Android emulator and launch it, glibc is already present in /system folder and just need to run the apps in glibc environment.
UPDATE
after I did as per Yuri mentioned in his answer (I created glibc folder and copied everything into it), when I compile the code I get below output.
build/core/main.mk:490: * Some files have been added to ALL_PREBUILT.
build/core/main.mk:491: *
build/core/main.mk:492: * ALL_PREBUILT is a deprecated mechanism that
build/core/main.mk:493: * should not be used for new files.
build/core/main.mk:494: * As an alternative, use PRODUCT_COPY_FILES in
build/core/main.mk:495: * the appropriate product definition.
build/core/main.mk:496: * build/target/product/core.mk is the product
build/core/main.mk:497: * definition used in all products.
build/core/main.mk:498: *
build/core/main.mk:499: * unexpected glibc in ALL_PREBUILT
build/core/main.mk:500: *
build/core/main.mk:501: * ALL_PREBUILT contains unexpected files. Stop.
So I added glibc in build/core/legacy_prebuilts.mk
But then I get
make: * No rule to make target mkdir', needed byout/target/product/generic/root/glibc'. Stop.

Finally I did it in a very unusual way.
I had 3 options:
Use BUILD_PREBUILT variable, but drawback it you can do it for a
single file, but I had multiple files and in a particular forlder
structure
Use PRODUCT_COPY_FILES. But somehow it was not working for me
PRODUCT_COPY_FILES is for a device, and it was not a new device for
me. I was working on emulator.
Using the solution given by Yuri, using ALL_PREBUILT +=, but as Yuri
mentioned it was for GB and I am using JB and ICS and hence was not
working for me.
The approach i took is to use shell script within the Android.mk file.
I used some like this:
Assume you have a folder named my_folder containing entire prebuilt folder structure which needs to be copied to anddroid out folder as is, inside my_folder, I created Android.mk and entered below text:
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
$(shell mkdir -p $(TARGET_OUT)/my_folder/)
$(shell cp -rf $(LOCAL_PATH)/* `pwd`/$(TARGET_OUT)/my_folder/)
This way all my prebuilt set of files and folders in my_folder directory were copied as is to system folder in android out.
I hope this helps someone.

PRODUCT_COPY_FILES must be placed in product mk files (device/mydevice/..), not module files (Android.mk). This is mentioned here.
This format is used for copying dirs:
PRODUCT_COPY_FILES += $(call find-copy-subdir-files,*,vendor/mydir,system/app)
This command is not working for apk files though, giving error:
build/core/Makefile: *** Prebuilt apk found in PRODUCT_COPY_FILES: vendor/mydir/ray-system-ui-release.apk:system/app/ui-release.apk, use BUILD_PREBUILT instead!. Stop.

Here is an example from the book "Embedded Android" that will help you. Create a folder in the root of your aosp project called rootfs-glibc, put there the code that you want to copy, and create there Android.mk file with the following content:
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
# This part is a hack, we're doing "addprefix" because if we don't,
# this dependency will be stripped out by the build system
GLIBC_ROOTFS := $(addprefix $(TARGET_ROOT_OUT)/, rootfs-glibc)
$(GLIBC_ROOTFS): mkdir -p $(TARGET_ROOT_OUT) cp -af $(TOPDIR)rootfs-glibc/* $(TARGET_ROOT_OUT) rm
# The last command just gets rid of this very .mk since it's copied as-is
ALL_PREBUILT += $(GLIBC_ROOTFS)
There is a note that this is true for Gingerbread. Maybe in newer versions of Android the make system has been changed.

Consider using a PHONY_PACKAGE with a custom installation step.
Unlike the $(shell cp whatever) answer above, this will only run during the installation step, rather than on every Make step (which is certainly not what you want).
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := some_module
LOCAL_ADDITIONAL_DEPENDENCIES := FORCE # Decide if you need this
LOCAL_POST_INSTALL_CMD = cd $(LOCAL_PATH) && cp -a mystuff $(TARGET_OUT_WHATEVER)
include $(BUILD_PHONY_PACKAGE)

I was thinking if I could do this way
1. I have both android and glibc compiled separetely.
2. Once both are compiled, I manually copy the glibc entire folder to /out/target/product/generic/system/glibc/ folder
3. Then I run "make snod"
Would that work?

Problems compiling avahi into Android NDK project

Over the last few days I've been having a difficult time trying to build avahi into a static or shared library for use with an existing Android NDK project.
We have a few games in the App and Play stores and my task is to get multiplayer working in the Android versions.
Specifically the task involves replacing the Bonjour component so that these games can connect to each other via zeroconf.
Research seemed to indicate that avahi is the lib that we're looking for, but at this point I'm open to anything that will work!
I'm hoping that someone here can either help me get avahi compiling or suggest another more appropriate (and easier to install) lib.
Project uses android-ndk-r8b and is being built on OSX 10.7.4 using command line (not eclipse)
Got the latest Avahi source from here:
http://www.linuxfromscratch.org/blfs/view/svn/basicnet/avahi.html
homebrewed all the necessary libs to get ./configure to run without errors.
./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var --disable-static --disable-mono --disable-monodoc --disable-gdbm --disable-libdaemon --disable-nls --disable-gtk --disable-gtk3 --disable-python --disable-qt3 --disable-qt4 --enable-core-docs --with-distro=none
./configure runs with no apparent red flags.
make results in this compile error:
socket.c: In function 'ipv6_pktinfo':
socket.c:271: warning: unused variable 'yes' [-Wunused-variable]
socket.c:270: warning: unused parameter 'fd' [-Wunused-parameter]
socket.c: In function 'avahi_send_dns_packet_ipv6':
socket.c:609: error: 'IPV6_PKTINFO' undeclared (first use in this function)
socket.c:609: error: (Each undeclared identifier is reported only once
socket.c:609: error: for each function it appears in.)
socket.c: In function 'avahi_recv_dns_packet_ipv6':
socket.c:869: error: 'IPV6_HOPLIMIT' undeclared (first use in this function)
socket.c:878: error: 'IPV6_PKTINFO' undeclared (first use in this function)
make[2]: *** [libavahi_core_la-socket.lo] Error 1
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2
Figured that it's not building against the android-ndk-r8b libs or finding ipv6.h or something.
Checked my .bash_profile.sh file:
export PATH=/Users/Muy01/Projects/Development/Android/android-sdks/tools/:$PATH
export PATH=/Users/Muy01/Projects/Development/Android/android-sdks/platform-tools/:$PATH
export PATH=/Users/Muy01/Projects/Development/Android/android-ndk-r8b/:$PATH
added --host=arm-linux-androideabi to the ./configure arguments list
resulting in this error:
checking host system type... Invalid configuration `arm-linux-androideabi': system `androideabi' not recognized
Couldn't figure out how to get a list of available host system types so changed direction and decided to try and build the static lib via Android.mk file.
Found this post on creating an appropriate Android.mk file:
can't compile avahi on android
Realized that I don't have Android.mk files within all the subdirectories.
Researched, downloaded, built, Androgenizer to try and convert all the Makefile.am files into Android.mk files.
http://cgit.collabora.com/git/user/derek/androgenizer.git/
Couldn't figure out or find info on how to do that though =/
Decided to try and create my own Android.mk file:
LOCAL_PATH := $(call my-dir)
ROOT_LOCAL_PATH :=$(call my-dir)
#Build avahi into a static lib
include $(CLEAR_VARS)
AVAHI_TOP := $(ROOT_LOCAL_PATH)/../avahi-0.6.31
MY_SOURCES := $(wildcard $(AVAHI_TOP)/avahi-core/*.c*)
MY_SOURCES += $(wildcard $(AVAHI_TOP)/avahi-common/*.c*)
LOCAL_C_INCLUDES := $(AVAHI_TOP)
LOCAL_SRC_FILES := $(MY_SOURCES:$(LOCAL_PATH)%=%)
LOCAL_MODULE := avahi
include $(BUILD_STATIC_LIBRARY)
Results in compile time errors for avahi-core/iface-linux.c:33:0:
/avahi-0.6.31/avahi-core/iface-linux.h:27:8: Redefinition of 'struct AvahiInterfaceMonitorOSDep'
/avahi-0.6.31/avahi-core/iface.h:46:16: Originally defined here
/avahi-0.6.31/avahi-core/iface-linux.h:33:9: Redeclaration of enumerator 'LIST_IFACE'
/avahi-0.6.31/avahi-core/iface.h:52:9: Previous definition of 'LIST_IFACE' was here
/avahi-0.6.31/avahi-core/iface-linux.h:34:9: Redeclaration of enumerator 'LIST_ADDR'
/avahi-0.6.31/avahi-core/iface.h:53:9: Previous definition of 'LIST_ADDR' was here
/avahi-0.6.31/avahi-core/iface-linux.h:35:9: Redeclaration of enumerator 'LIST_DONE'
/avahi-0.6.31/avahi-core/iface.h:54:9: Previous definition of 'LIST_DONE' was here
/jni//../avahi-0.6.31/avahi-core/iface-linux.c: In function 'netlink_callback':
And now I'm pretty much stuck.
I tried #if 0'ing out the iface-linux.c and h files resulting in a cascading slew of other errors, so prob a bad idea.
Thinking that it may be something I've done wrong with the ./configure command?
Perhaps an issue with my Android.mk file?
I figure this must be something that quite a few developers are dealing with so I'm probably missing something because I can't seem to find any good information via google.
Any help would be much appreciated!
I've sent this out to the avhi mailing list as well, if I get a response there I will post here for posterity.
Thanks,
Chris

I'll follow up here with the solution that worked for me.
My solution was to use JMDNS instead of Avahi.
There's not much traffic on the Avahi mailing list.
JMDNS has working examples available.
JMDNS took me about 4 hours to set up within my NDK environment and about a day to work out some "kinks."

tar avahi-0.6.31
patch -p1 < 0001-Add-Android-support.patch
patch -p1 < 0002-Add-uninstalled.pc.in-files.patch
cd avahi-0.6.31
./configure --sysconfdir=/etc --localstatedir=/var
make
cd the subdirectories: make Android.mk
then, you will see Android.mk in all the subdirectories.
ndk-build V=1 NDK_LOG=2 APP_ABI="armeabi armeabi-v7a"

Compiling linked ( not copied ) files using NDK

I'm building an OpenGL based app - writing in native C/C++.
I want to have my native files in a single location and only linked to the project ( so when I edit them in XCode/Eclipse the other project already has the updated files ). However, I can't figure out how to get ndk-build to build files that aren't actually in the JNI folder. Symbolic links ( in OSX ) didn't do the trick.
I keep getting
make: *** No rule to make target `/Developer/SDKs/android-ndk-r7b/build/core/myfile.cpp', needed by `obj/local/armeabi/objs/glHelloArrow/myfile.o'. Stop.
Any ideas?

I build outside of JNI folder on Windows. My Android.mk includes a makefile in a different folder:
LOCAL_PATH := $(MY_WORKSPACE)/path/jni
include $(MY_WORKSPACE)/path/jni/Src.mk
where the actual sources are listed:
LOCAL_SRC_FILES := \
a.cpp \
b.cpp \
etc.
One caveat is - make does not work right with relative paths. Or rather, it does, but assumes the path to be relative to the current folder, which in case of the ndk-build process can be all over the place. Thus the env variable that denotes the root of the file location.
Some details here.

I have a similar issue with cross-platform codebase. I've not found any way to do this.
My workaround is to create a symlink from my source code root directory into jni, so I can give the NDK build system paths like jni/link/common/foo.c.
Just be sure that you remove the symlink if you ever need to run tools that do recursive directory traversals...