Linking with versioned shared library in Android NDK

Question

I am trying to load two shared libraries in my Android application through the loadLibrary call:

System.loadLibrary("mywrapper");
System.loadLibrary("crypto");

I keep running catching the `UnsatisfiedLinkError. Here is a more detailed version of the error.

Caused by: java.lang.UnsatisfiedLinkError: Cannot load library: link_image[1969]:
  130 could not load needed library 'libcrypto.so.1.0.0' for 
  'libmywrapper.so' (load_library[1111]: Library 'libcrypto.so.1.0.0' not found)

Any ideas?

After spending some time I found out that Android doesn't support versioned libraries. Has any one faced the same issue?

score 6 · Answer 1 · answered May 19 '15 at 06:02

I had the same problem on building libwebsockets for Android, which needs to link with OpenSSL. I use libssl.so as example. You should do the same for related .so files.

Before:
huiying@huiying-PORTEGE-R835:~$ objdump -p libssl.so | grep so
libssl.so:     file format elf32-little
  NEEDED               libcrypto.so.1.0.0
  NEEDED               libdl.so
  NEEDED               libc.so
  SONAME               libssl.so.1.0.0

After 
huiying@huiying-PORTEGE-R835:~$ rpl -R -e .so.1.0.0 "_1_0_0.so" libssl.so 
Replacing ".so.1.0.0" with "_1_0_0.so" (case sensitive) (partial words matched)
.
A Total of 2 matches replaced in 1 file searched.
huiying@huiying-PORTEGE-R835:~$ objdump -p libssl.so | grep so
libssl.so:     file format elf32-little
  NEEDED               libcrypto_1_0_0.so
  NEEDED               libdl.so
  NEEDED               libc.so
  SONAME               libssl_1_0_0.so

And don't forget to change file name "libssl.so" to "libssl_1_0_0.so".

The hack works. I have running Android app to prove it. See my rant at http://computervisionandjava.blogspot.com/2015/05/trouble-with-versioned-shared-libraries.html.

I wasn't able to get rpl to work with the .so files, but I was able to just edit the file with VIM and do the string replace there. Great hack. Thanks! — Xample, Feb 08 '17 at 14:57

feverDream · Answer 2 · 2012-07-17T10:17:32.360

It seems android has an issue with loading versioned libraries.The issue at hand was because of library so-name in my case libcrypto.so.1.0.0. Even if you rename the library and try to load it as a prebuilt shared library in an android make file it fails.( It has to be because the library name is somehow embedded in the file. And any library that links with it expects to be linked with a library of with the same name )

I hope there are other ways out there when it comes to handling libraries with version names in android.

For now I am evading the problem all together by using static libraries of openssl and linking them with my own shared library.

score 2 · Answer 3 · answered Sep 23 '14 at 19:15

Year 2014 and still no support for versioned shared libs. So I made a script to patch SONAME. Just point the script to input dir where all versioned libs placed. Then check output dir "unver".

#!/bin/bash

DIR="$1"

if [ "$DIR" == "" ]; then
    echo "Usage: fix-soname.sh <target dir>"
    exit
fi

if [ ! -d $DIR ]; then
    echo "Not found: $DIR"
    exit
fi

OUT="$DIR/unver"
echo "Input=$DIR"
echo "Output=$OUT"

CWD=$(pwd)
cd $DIR

# prep dirs
mkdir -p $OUT
rm -f -R $OUT/*

# rename libs and copy to out dir
find "$DIR" -type f -name '*.so*' | while read FILE; do

    NAME=$(basename "$FILE")
    SONAME=$NAME

    while read SYMLINK; do
        X=$(basename "$SYMLINK")
        #echo "$X (${#X}) -> $NAME (${#NAME})"
        if [ "${#X}" -lt "${#SONAME}" ]; then
            SONAME=$X
        fi
done<<EOT
`find -L $DIR -samefile $FILE`
EOT

    #echo $SONAME
    cp -f $SONAME $OUT/
done

# patch libs in out dir
find "$OUT" -type f -name '*.so*' | while read FILE; do

    # get file name without path
    NAME=$(basename "$FILE")

    # extract SONAME from shared lib
    SONAME=`readelf -d $FILE | grep '(SONAME)' | grep -P '(?<=\[)(lib.*?)(?=\])' -o`

    #echo "$NAME [$SONAME]"

    # patch SONAME if required
    if [ "$NAME" != "$SONAME" ]; then
        L1=${#NAME}
        L2=${#SONAME}
        LDIFF=$((L2-L1))
        #echo "$NAME [$SONAME] ($LDIFF)"

        if [ "$LDIFF" -gt "0" ]; then
            SONEW=$NAME
            for (( c=1; c<=$LDIFF; c++ )); do
                SONEW+="\x00"
            done
            echo "$NAME [$SONAME] -> $SONEW ($LDIFF)"
            rpl -R -e "$SONAME" "$SONEW" $OUT
        fi
    fi
done

cd $CWD

it didnt work for me... i ran it on openssl source dir, with the binaries compiled and the 'unver' dir output is exactaly the same as the original binary libcrypto.so — Giovani, Feb 13 '15 at 11:48
You can uncomment #echo in script and see where something goes wrong. — sviborg, Feb 14 '15 at 12:43

Linking with versioned shared library in Android NDK

3 Answers3

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