Collectives™ on Stack Overflow

Find centralized, trusted content and collaborate around the technologies you use most.

Teams

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

Now that Android Studio 2.2 is released officially, I'm migrating from my old ndk-build process to try and use CMake within AS. As I'm incorporating several codebases from within my company (that I can't edit) that make heavy use of C++11 code (including the dreaded std::to_string() method), the only way I can compile is with a select few configuration options - all of which I discovered earlier when beginning work with ndk-build. (see below)

So everything compiles again and builds into the APK - and I 100% verify that my output shared library exists in the APK, but I'm unable to successfully use System.loadLibrary('mylibrary') - and it turns out this is because the dependency libc++_shared.so is missing.

As in, I get the following error:

java.lang.UnsatisfiedLinkError: dlopen failed: library "libc++_shared.so" not found
In my old ndk-build process, I always wound up with the 2 libraries (mylibrary.so and libc++_shared.so) in my output folder, which thereby got bundled together into the app. It seems the CMake toolchain isn't bundling libc++_shared.so at all (indeed, it's not found in the APK). 
I've been banging my head on this for 6 hours. Can I somehow get the CMake toolchain to bundle this missing library? Any clues?
My settings:
In gradle.build:
externalNativeBuild {
        cmake {
            arguments '-DANDROID_STL=c++_shared', '-DANDROID_TOOLCHAIN=gcc', '-DANDROID_PLATFORM=android-16'
And my CMakeLists.txt (filenames cut out for brevity):
cmake_minimum_required(VERSION 3.4.1)
set(CMAKE_CXX_FLAGS "${CMAKE_C_FLAGS} -std=gnu++11")
include_directories(.)
include_directories(./other)
set(my_SRCS jniInterface.cpp
    etc.cpp)
add_library(mylibrary SHARED ${my_SRCS})
target_link_libraries(mylibrary atomic log)
                This is a known issue in the Android Studio CMake integration: code.google.com/p/android/issues/detail?id=214664
– Dan Albert
                Sep 21, 2016 at 20:24
                you might try to see if this one: github.com/googlesamples/android-ndk/pull/298  could work for you. there might be more than this to be done, give it a try to see if it could help you for the moment
– Gerry
                Sep 21, 2016 at 22:11
                Thanks @Gerry that does indeed work. I might formulate the changes I made into an alternative answer to this thread.. :-)
– Mete
                Sep 22, 2016 at 9:16
                For some reason you must also also use -DANDROID_ARM_NEON=1, or the library won't be bundled, perhaps it depends on neon or whatever.
– user823738
                Sep 13, 2019 at 10:30
                what is the diff between "package 'libc++_shared.so' in the apk file" and linking libc++_shared.so to my target?
– Vivek Mangal
                Jun 4, 2022 at 18:59
I wrote a CMake config that should package the STL files:
https://github.com/jomof/ndk-stl/blob/master/ndk-stl-config.cmake
Copy this file next to your CMakeLists.txt and inside CMakeLists.txt do 
include(ndk-stl-config.cmake)
Let me know if you have problems
                Thanks man, I like the look of this but keep running into the error 'Could not find a package configuration file provided by "ndk-stl"' - I tried changing PATHS "." to PATHS ${CMAKE_CURRENT_LIST_DIR} but still no luck. Will keep trying in the meantime...
– Mete
                Sep 22, 2016 at 8:52
                Note, although I found another workaround to the problem, I think yours looks easier and more portable if it works, so I would give you the answer if we can figure out that paths issue
– Mete
                Sep 22, 2016 at 9:34
                That message means CMake couldn't locate the package file ndk-stl-config.cmake. Did you name the file ndk-stl-config.cmake and place it next to your CMakeLists.txt? If so, hmmm, two ideas: (1) share a repro project with me on github, (2) paste the full message that you got (build with ./gradlew assemble on command-line)
– Jomo Fisher
                Sep 22, 2016 at 14:39
                EDIT: I accepted Gerry's suggestion to use include(...) instead of find_package(...). He confirmed this worked from his side.
– Jomo Fisher
                Sep 22, 2016 at 19:41
                this works great, changed sample to use this one: it is much cleaner implementation!  thanks
– Gerry
                Sep 22, 2016 at 20:29
            cmake {
                cppFlags "-std=c++14 -fexceptions -frtti"
                arguments "-DANDROID_ARM_NEON=TRUE",'-DANDROID_STL=c++_shared'
                @kakyo There is no flag named 'cppFlags' or 'arguments' : google.github.io/android-gradle-dsl/current/…  How did you get this to work?
– Alan
                Feb 10, 2020 at 22:11
As Gerry pointed out, the latest changes to the audio-echo sample project (https://github.com/googlesamples/android-ndk/pull/298) include changes that worked for me. I added this to the bottom of my CMakeLists.txt file. 
# Android Studio CMake does not pack stl shared libraries, so app needs to pack
# the right shared lib into APK. The following code find right stl type and copy
# the needed shared lib into app's app/src/main/jniLibs, android studio assembles
# it into the final APK
# Helper function to retrieve shared stl path and name in NDK
# stl_path: the path to the NDK's shared lib path; empty if not using shared stl
function(get_stl_info stl_path stl_name)
   # assume app not uses shared stl lib
   set(${stl_path} "" PARENT_SCOPE)
   if(NOT ${ANDROID_STL} MATCHES "_shared")
       return()
   endif()
   # using shared lib, config lib name and path
   if("${ANDROID_STL}" MATCHES "c\\\+\\\+_")
       # app uses c++_shared for stl type
       set(stlPath "llvm-libc++/libs/${ANDROID_ABI}")
       set(stlName "libc++_shared.so")
   elseif(${ANDROID_STL} MATCHES "gnustl_")
       set(stlPath "gnu-libstdc++/4.9/libs/${ANDROID_ABI}")
       set(stlName "libgnustl_shared.so")
   else()
       # this sample not supporting other stl types
       message(FATAL_ERROR "Not Suppored STL type: ${ANDROID_STL}")
       return()
   endif()
   set(${stl_path} ${ANDROID_NDK}/sources/cxx-stl/${stlPath} PARENT_SCOPE)
   set(${stl_name} ${stlName} PARENT_SCOPE)
endfunction()
# force copying needed shared stl lib into ${project}/app/src/main/jniLibs
# so it will be packed into APK
get_stl_info(ndk_stl_path  ndk_stl_name)
if(NOT ${ndk_stl_path} STREQUAL "")
    set(jniLibs_dir "${CMAKE_CURRENT_SOURCE_DIR}/../jniLibs")
    add_custom_command(TARGET mylibrary PRE_BUILD
                   COMMAND "${CMAKE_COMMAND}" -E
                   copy ${ndk_stl_path}/${ndk_stl_name}
                   "${jniLibs_dir}/${ANDROID_ABI}/${ndk_stl_name}"
                   COMMENT "Copying Shared library to the packing directory")
endif()
I guess it's a workaround that we'll be able to do without some day... Note you have to change the line add_custom_command(TARGET mylibrary PRE_BUILD and replace mylibrary with your target name.
        
Thanks for contributing an answer to Stack Overflow!
Please be sure to answer the question. Provide details and share your research!
But avoid …
Asking for help, clarification, or responding to other answers.
Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.