Linking external libraries to Android native shared library

[purvi]

Hi,

I have a question. To include any external library whether a static
library (*.a) or shared library (*.so) and link to the current native
shared library I have to inlcude the below code in my Andriod.mk

include $(CLEAR_VARS)

LOCAL_PREBUILT_LIBS:= libexternal1.a

include $(BUILD_MULTI_PREBUILT)

include $(CLEAR_VARS)

LOCAL_MODULE:=mynativeexample

LOCAL_SRC_FILES:=myexample.c

LOCAL_STATIC_LIBRARIES:=libexternal1

include $(BUILD_SHARED_LIBRARY)

The library libexternal1.a is compiled and build outside android. and
resides in the directory same as the path of my Andriod.mk
The path is \android-ndk-1.6_r1\apps\MyApplication\project\jni\.

And I am getting an error : No rule to make target 'out/apps/
MyApplication//libexternal1.a' needed to make 'out/apps/
MyApplication//
mynativeexample.so'
If I copy the libexternal1.a to 'out/apps/MyApplication//' it gives me
error
'out/apps/MyApplication//libexternal1.a' : file not recognized: File
format not recognized
As per few android-ndk threads I went thru it is improper to copy the
libexternal1.a to the out directory as the library should be
automatically created in the 'out' directory.
Something is missing in my Android.mk or something related to path of
my external static library.

The same error occurs when I use a shared library instead of static
library.

Can anyone please help me why is this happening and how to solve
this.?

Thanks.
Regards,
Purvi

[northfork]

how was your external library compiled?
it should be made with android tools to match the platform you are
making for.

[purvi]

I used gcc to compile and build external library.

> > Purvi- Hide quoted text -
>
> - Show quoted text -

[purvi]

Hi,

So is it that I have to use arm-eabi-gcc compiler to compile a C
source code and build a static or shared library out of it and use it
in my Android.mk. Or can I include the C source code (not the native
code) in my Android.mk as a module?

Thanks.
Regards,
Purvi

> > - Show quoted text -- Hide quoted text -

[David Turner]

LOCAL_PREBUILT_LIBS is not supported by the NDK build system.

It is a feature of the full Android build system which is very differently implemented.

Try adding the path to your prebuilt static library to your LOCAL_LDLIBS instead.

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[purvi]

Ok. Earlier I did try with LOCAL_LDLIBS:= -lexternall to add my
precompiled library. The externall.a is compiled using gcc and the
path to this library is \android-ndk-1.6_r1\build\platforms
\android-4\arch-arm\usr\lib. I came across that LOCAL_LDLIBS is only
used to access the libraries provided by Android NDK not any other
external precompiled library. So When I place my externall.a at the
above path it gives me error : externall.a : file not recognized:File
format not recognized.

Is there a different way to deal with this?

> Try adding the path to your prebuilt static library to your LOCAL_LDLIBS
> instead.

I retied modifying my Android.mk for LOCAL_LDLIBS. The problem still
persists.
Can anyone please help me out with this?

Thanks.
Regards,
Purvi

[David Turner]

On Thu, Jan 7, 2010 at 7:01 AM, purvi <purvi...@gmail.com> wrote:

Ok. Earlier I did try with LOCAL_LDLIBS:= -lexternall to add my
precompiled library. The externall.a is compiled using gcc and the
path to this library is \android-ndk-1.6_r1\build\platforms
\android-4\arch-arm\usr\lib. I came across that LOCAL_LDLIBS is only
used to access the libraries provided by Android NDK not any other
external precompiled library. So When I place my externall.a at the
above path it gives me error : externall.a : file not recognized:File
format not recognized.

You don't need to use -lexternall and modify anything under build/platforms,

just use the path to the static library as in some/directory/libexternall.a instead on your LOCAL_LDLIBS line.

On the other handm the "File format not recognized" probably means that there is something wrong with your

static library. How was it generated exactly ? Did you use a cross-compiler that targets ARMv5TE for example ?

 

Is there a different way to deal with this?

> Try adding the path to your prebuilt static library to your LOCAL_LDLIBS
> instead.

I retied modifying my Android.mk for LOCAL_LDLIBS. The problem still
persists.
Can anyone please help me out with this?

Thanks.
Regards,
Purvi

[purvi]

ok. I get the idea how to include the external library.

I used gcc to generate the library. As a suggestion given to me by a
group member, the reason for the file not recognized error is that it
is not compatible with the toolchain. So I tried to use the arm-eabi-
gcc to compile the static libraries but the library was not created.
Can you please tell me how can I compile it to be compatible?

Thanks.
Regards,
Purvi

On Jan 7, 12:30 pm, David Turner <di...@android.com> wrote:

> > android-ndk...@googlegroups.com<android-ndk%2Bunsubscribe@googlegr­oups.com>

> > .
> > For more options, visit this group at

> >http://groups.google.com/group/android-ndk?hl=en.- Hide quoted text -

[David Turner]

On Thu, Jan 7, 2010 at 10:30 AM, purvi <purvi...@gmail.com> wrote:

ok. I get the idea how to include the external library.

I used gcc to generate the library. As a suggestion given to me by a
group member, the reason for the file not recognized error is that it
is not compatible with the toolchain. So I tried to use the arm-eabi-
gcc to compile the static libraries but the library was not created.
Can you please tell me how can I compile it to be compatible?

There really is too much detail to give if you don't know the difference between a compiler and cross-compiler.

I instead recommend you to write an Android.mk file to build your sources instead and use the NDK to handle

all of the nasty details instead.

Hope this helps

To unsubscribe from this group, send email to android-ndk...@googlegroups.com.

[purvi]

Thank you for the guidance it was quite helpful.

> There really is too much detail to give if you don't know the difference
> between a compiler and cross-compiler.

I was able to make out the diff between compiling and cross
compiling.
Can you please tell me how can we crosscompile any assembly source
code.

> I instead recommend you to write an Android.mk file to build your sources
> instead and use the NDK to handle
> all of the nasty details instead.

Actually yes I tried this option at the very first time, but the C
source code have some assembly code as well.
So when I include the assembly source in Android.mk it is giving me
error Bad instructions on each line of my assembly code.
The same is true when I tried to cross compile the assembly code with
arm-none-eabi-gcc.

Thanks.
Regards,
Purvi

[David Turner]

Make the assembly source names end with .S instead of .c

This will instruct the compiler to pre-process them and later run through the result directly through the assembler.

If you use the NDK, simply do something like:

LOCAL_SRC_FILES := foo.c bar.S

to build foo.c as a C source file and bar.S as an assembler file.

If you have inlined assembler within a C source code, it probably is compiler-specific and something tells me it's not

compatible with gcc anyway.

[purvi]

> If you use the NDK, simply do something like:
>
> LOCAL_SRC_FILES := foo.c bar.S
>
> to build foo.c as a C source file and bar.S as an assembler file.
>

Yes, that is exactly what I am doing in my Android.mk. I placed all my
c source and assembly source in LOCAL_SRC_FILES in the order of their
dependencies. it is giving me error Bad instructions on each line of
my assembly code. If you can please help to understand the reason for
it and any solution to this error.

> If you have inlined assembler within a C source code, it probably is
> compiler-specific and something tells me it's not
> compatible with gcc anyway.
>

There is no inline assembly code in my C code.

Thank you for the guidance. It is really helpful.

Regards,
Purvi

[David Turner]

You will have to provide at least a sample assembly source file so we can have a look at it.

Are you sure it's ARM assembly ?