Hi,
You might have missed the linker option. Please make sure that your
library doesn't use the default linux linker; /lib/ld-linux.so.2 , if
it's used then you are in trouble. You have to use the custom linker and
build your library from scratch and check regularly for the
functionality. Most of the default C/C++ stuff are missing in the
Android platform, so you might spend a whole lot of time and then
finally get into trouble. I'm writing you because same thing happened to
me. Please make sure if there is a list of available functions in the
platform as well, if you are using some functions from the Android platform.
I'm quite sure this problem is due to the incompatibility of the
libraries. So, I advise you to hit ldd, and check the libraries it loads.
Thanks,
Diluka.
Ashutosh wrote:
> Hello All,
>
> I am trying to call an API in a C++ library libNativeCpp.so and
> Android does not load it. The error is --
>
> DEBUG/dalvikvm(1185): LOADING path /system/lib/libNativeCpp.so
> 0x4001f6e8
> INFO/dalvikvm(1185): Unable to dlopen(/system/lib/libNativeCpp.so):
> Cannot find library
>
> I have used arm-2008q1/bin/arm-none-linux-gnueabi-gcc, arm-2008q1/bin/
> arm-none-linux-gnueabi-g++ for compilation.
>
> How I tried to do that is explained below --
>
> I have gone through the URL
> http://davanum.wordpress.com/2007/12/09/android-invoke-jni-based-methods-bridging-cc-and-java/
> and have been able to run the program successfully.
>
> After this I have made some changes in the source code.
> 1) I have changed signature of function add() in class NativeAdd. It
> is now 'public static native long add(int a, int b)'.
> 2) I have changed function Java_org_apache_NativeAdd_add() in file
> org_apache_NativeAdd.c. It now looks like --
>
> #include "org_apache_NativeAdd.h"
>
> JNIEXPORT jlong JNICALL Java_org_apache_NativeAdd_add
> (JNIEnv *env, jclass c, jint a, jint b)
> {
> long aa;
> aa = ret_mul(a, b);
> // aa = ret_mul_cpp(a, b);
> return aa;
> }
>
> The function ret_mul() is written in another file called NativeC.c.
> Content of file is --
> #include <stdio.h>
> int ret_mul(int a, int b)
> {
> return (a * b);
> }
>
> Now I compile these files and create libraries --
>
> arm-none-linux-gnueabi-gcc -I /usr/java/jdk1.6.0_04/include -I /usr/
> java/jdk1.6.0_04/include/linux -fpic -c org_apache_NativeAdd.c
> arm-none-linux-gnueabi-ld -T armelf_linux_eabi.xsc -shared -o
> libNativeAdd.so org_apache_NativeAdd.o
>
>
> arm-none-linux-gnueabi-gcc -fpic -c NativeC.c
> arm-none-linux-gnueabi-ld -T armelf_linux_eabi.xsc -shared -o
> libNativeC.so NativeC.o
>
> The file armelf_linux_eabi.xsc is modified as per the suggestion on
> the URL
> http://honeypod.blogspot.com/2007/12/shared-library-hello-world-for-android.html
> .
>
> I pushed the library to android environment --
> adb push libNativeAdd.so /system/lib
> adb push libNativeC.so /system/lib
>
> I have created an android project CallNative1 and in file
> NativeAdd.java, I am loading libraries as below --
> System.loadLibrary("NativeC");
> System.loadLibrary("NativeAdd");
>
> When I run the project CallNative1, it prints the result as
> multiplication of two integers.
>
> Now I write the same ret_mul() function in NativeCpp.cpp. Content of
> NativeCpp.cpp is --
>
> #include <iostream>
> int ret_mul_cpp(int a, int b)
> {
> return (a * b);
> }
>
> Compiled it --
>
> arm-none-linux-gnueabi-g++ -fpic -c NativeCpp.cpp
> arm-none-linux-gnueabi-ld -T armelf_linux_eabi.xsc -shared -o
> libNativeCpp.so NativeCpp.o
>
> Pushed the library --
>
> adb push libNativeCpp.so /system/lib
>
> Now loading libraries as below --
>
> System.loadLibrary("NativeCpp");
> System.loadLibrary("NativeAdd");
>
>
> When I run CallNative1 again I can see below errors in logcat.
>
> DEBUG/dalvikvm(1185): LOADING path /system/lib/libNativeCpp.so
> 0x4001f6e8
> INFO/dalvikvm(1185): Unable to dlopen(/system/lib/libNativeCpp.so):
> Cannot find library
>
>
> Below are the information about symbols in both the libraries --
>
>
> arm-none-linux-gnueabi-nm libNativeC.so
> 00000244 a _DYNAMIC
> 0000029c a _GLOBAL_OFFSET_TABLE_
> 000002a8 A __bss_end__
> 000002a8 A __bss_start
> 000002a8 A __bss_start__
> 000002a8 D __data_start
> 000002a8 A __end__
> 00000244 A __exidx_end
> 00000244 A __exidx_start
> 000002a8 A _bss_end__
> 000002a8 A _edata
> 000002a8 A _end
> 00000214 T ret_mul
>
>
> arm-none-linux-gnueabi-nm libNativeCpp.so
> =========================================
> 000007a0 a _DYNAMIC
> 00000840 a _GLOBAL_OFFSET_TABLE_
> 000006ec t _GLOBAL__I__Z11ret_mul_cppii
> 00000460 T _Z11ret_mul_cppii
> 00000640 t _Z41__static_initialization_and_destruction_0ii
> U _ZNKSs4sizeEv
> U _ZNKSsixEj
> U _ZNSt8ios_base4InitC1Ev
> U _ZNSt8ios_base4InitD1Ev
> 00000490 t _ZSt17__verify_groupingPKcjRKSs
> 00000708 W _ZSt3minIjERKT_S2_S2_
> 00000868 b _ZSt8__ioinit
> U __aeabi_atexit
> U __aeabi_unwind_cpp_pr0
> U __aeabi_unwind_cpp_pr1
> 0000086c A __bss_end__
> 00000868 A __bss_start
> 00000868 A __bss_start__
> 00000868 B __data_start
> U __dso_handle
> 0000086c A __end__
> 0000079c A __exidx_end
> 00000774 A __exidx_start
> 0000086c A _bss_end__
> 00000868 A _edata
> 0000086c A _end
>
> I have gonr through the discussion at
> http://groups.google.com/group/android-internals/browse_thread/thread/780ba5316409cf5d
> and I also feel that the problem is with unresolved symbols.
>
> I pulled whole /system directory from Android and treid to grep one of
> the undefined symbols _ZNKSs4sizeEv, in /system but could not find it.
> But if I grep them in arm-2008q1 directory I find many matches.
>
> grep -r _ZNKSs4sizeEv arm-2008q1/*
> Binary file arm-2008q1/arm-none-linux-gnueabi/libc/armv4t/usr/lib/
> libstdc++.so.6 matches
> Binary file arm-2008q1/arm-none-linux-gnueabi/libc/armv4t/usr/lib/
> libstdc++.a matches
> Binary file arm-2008q1/arm-none-linux-gnueabi/libc/armv4t/usr/lib/
> libstdc++.so.6.0.9 matches
> Binary file arm-2008q1/arm-none-linux-gnueabi/libc/armv4t/usr/lib/
> libstdc++.so matches
> Binary file arm-2008q1/arm-none-linux-gnueabi/libc/thumb2/usr/lib/
> libstdc++.so.6 matches
> Binary file arm-2008q1/arm-none-linux-gnueabi/libc/thumb2/usr/lib/
> libstdc++.a matches
> Binary file arm-2008q1/arm-none-linux-gnueabi/libc/thumb2/usr/lib/
> libstdc++.so.6.0.9 matches
> Binary file arm-2008q1/arm-none-linux-gnueabi/libc/thumb2/usr/lib/
> libstdc++.so matches
> Binary file arm-2008q1/arm-none-linux-gnueabi/libc/usr/lib/libstdc+
> +.so.6 matches
> Binary file arm-2008q1/arm-none-linux-gnueabi/libc/usr/lib/libstdc++.a
> matches
> Binary file arm-2008q1/arm-none-linux-gnueabi/libc/usr/lib/libstdc+
> +.so.6.0.9 matches
> Binary file arm-2008q1/arm-none-linux-gnueabi/libc/usr/lib/libstdc+
> +.so matches
>
> I don't know why these symbols are not there in /system/lib at
> android. Statically linking a C++ library is not advisable.
>
> Could anyone please suggest me how do I go about it ?
>
> Thanks
> Ashutosh
>
>
>
> >
>
>
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