Android ndk static linking to openssl failed with BIO_new_dgram undefined - android-ndk

Question

I built libssl.a and libcryto.a. But when I want to link my.so to it, I got this error:
Error:(130) undefined reference to 'BIO_new_dgram'
If I delete this call, I can compile it succeed.
Did I build the library of openssl in a wrong way?
BIO_new_dgram is in libcrypto.a:
nm libcrypto.a | grep BIO_new_dgram
0000081c T BIO_new_dgram
I configure Openssl with:
./config shared --openssldir=$install_dir --prefix=$install_dir
and link command:
/home/choury/bin/Android/android-sdk-linux/ndk-bundle/toolchains/llvm/prebuilt/l
inux-x86_64/bin/clang++ --target=aarch64-none-linux-android --gcc-toolchain=/ho
me/choury/bin/Android/android-sdk-linux/ndk-bundle/toolchains/aarch64-linux-andr
oid-4.9/prebuilt/linux-x86_64 --sysroot=/home/choury/bin/Android/android-sdk-lin
ux/ndk-bundle/platforms/android-21/arch-arm64 -fPIC -std=c++11 -Wall -fPIC -ggdb
-O0 -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-und
efined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -Wl,--build
-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noe
xecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -shared -Wl,-soname,my.so -o
$outpath/my.so $mypath/a.o $mypath/b.o $install_dir/lib/libssl.a $install_dir/li
b/libcrypto.a -ldl my.a -lz -llog -lm "/home/choury/bin/Android/android-sdk-linux
/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/libs/arm64-v8a/libsupc++.a" "/home/
choury/bin/Android/android-sdk-linux/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9
/libs/arm64-v8a/libgnustl_shared.so"
I build the project with cmake, the Openssl part of it:
set(OPENSSL_INCLUDE_DIR ${OPENSSL_ROOT_DIR}/include)
set(OPENSSL_LIBRARIES ${OPENSSL_ROOT_DIR}/lib)
set(OPENSSL_CRYPTO_LIBRARY ${OPENSSL_LIBRARIES}/libcrypto.a)
set(OPENSSL_SSL_LIBRARY ${OPENSSL_LIBRARIES}/libssl.a)
find_package(OpenSSL REQUIRED IMPORTED)
The OPENSSL_ROOT_DIR is set with $install_dir in build.gradle.

Answer 1

The linker in NDK is sensitive to the order of static libraries on command line. If libA.a depends on libB.a, the command line should be
clang++ … a.o b.o a/libA.a b/libB.a … -Llibs -lm -ldl -lz -llog -o libqq.so
here I assume libm.so, libdl.so, libz.so and liblog.so. Note that the following command is equivalent:
clang++ … a.o b.o -La -lA -Lb -lB … -Llibs -lm -ldl -lz -llog -o libqq.so