CMake测试被忽略-在Android中使用Gradle构建CMake项目

Question

I'm trying to integrate https://github.com/j0r1/JRTPLIB into gradle. There's already a tutorial on the readme about how to compile the library to installation on Android, but I need gradle integration.

Here's how I added the project to my gradle file:

https://github.com/lucaszanella/jscam/blob/ecc99f430b360f7e1aa5bf687633a5e3557c045e/src/jscam/android/app/build.gradle#L118

I'm getting a compilation error because my system libs don't have support for ifaddrs . However, the cmakelists of the project has a test for that:

jrtplib_include_test(ifaddrs.h RTP_SUPPORT_IFADDRS "// No ifaddrs support")

So why is gradle trying to build something that didn't pass the test?

Here's the error while compiling my app:

Error while executing '/android-sdk-linux/cmake/3.6.4111459/bin/cmake' with arguments {--build /home/project/src/jscam/android/app/.externalNativeBuild/cmake/debug/x86 --target jrtplib-shared}
  [1/3] Building CXX object src/CMakeFiles/jrtplib-shared.dir/rtpudpv4transmitter.cpp.o
  [2/3] Building CXX object src/CMakeFiles/jrtplib-shared.dir/rtpudpv6transmitter.cpp.o
  FAILED: /android-sdk-linux/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++  --target=i686-none-linux-android --gcc-toolchain=/android-sdk-linux/ndk-bundle/toolchains/x86-4.9/prebuilt/linux-x86_64 --sysroot=/android-sdk-linux/ndk-bundle/sysroot  -DJRTPLIB_COMPILING -Djrtplib_shared_EXPORTS -I/home/project/src/jscam/JRTPLIB/src -Isrc -isystem /android-sdk-linux/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/include -isystem /android-sdk-linux/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/libs/x86/include -isystem /android-sdk-linux/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/include/backward-isystem /android-sdk-linux/ndk-bundle/sysroot/usr/include/i686-linux-android -D__ANDROID_API__=16 -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -mstackrealign -Wa,--noexecstack -Wformat -Werror=format-security   -O0 -fno-limit-debug-info  -fPIC -MD -MT src/CMakeFiles/jrtplib-shared.dir/rtpudpv6transmitter.cpp.o -MF src/CMakeFiles/jrtplib-shared.dir/rtpudpv6transmitter.cpp.o.d -o src/CMakeFiles/jrtplib-shared.dir/rtpudpv6transmitter.cpp.o -c /home/project/src/jscam/JRTPLIB/src/rtpudpv6transmitter.cpp
  /home/project/src/jscam/JRTPLIB/src/rtpudpv6transmitter.cpp:1575:2: error: use of undeclared identifier 'getifaddrs'
          getifaddrs(&addrs);
          ^
  /home/project/src/jscam/JRTPLIB/src/rtpudpv6transmitter.cpp:1588:2: error: use of undeclared identifier 'freeifaddrs'
          freeifaddrs(addrs);
          ^
  2 errors generated.
  FAILED: /android-sdk-linux/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++  --target=i686-none-linux-android --gcc-toolchain=/android-sdk-linux/ndk-bundle/toolchains/x86-4.9/prebuilt/linux-x86_64 --sysroot=/android-sdk-linux/ndk-bundle/sysroot  -DJRTPLIB_COMPILING -Djrtplib_shared_EXPORTS -I/home/project/src/jscam/JRTPLIB/src -Isrc -isystem /android-sdk-linux/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/include -isystem /android-sdk-linux/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/libs/x86/include -isystem /android-sdk-linux/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/include/backward-isystem /android-sdk-linux/ndk-bundle/sysroot/usr/include/i686-linux-android -D__ANDROID_API__=16 -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -mstackrealign -Wa,--noexecstack -Wformat -Werror=format-security   -O0 -fno-limit-debug-info  -fPIC -MD -MT src/CMakeFiles/jrtplib-shared.dir/rtpudpv4transmitter.cpp.o -MF src/CMakeFiles/jrtplib-shared.dir/rtpudpv4transmitter.cpp.o.d -o src/CMakeFiles/jrtplib-shared.dir/rtpudpv4transmitter.cpp.o -c /home/project/src/jscam/JRTPLIB/src/rtpudpv4transmitter.cpp
  /home/project/src/jscam/JRTPLIB/src/rtpudpv4transmitter.cpp:1813:2: error: use of undeclared identifier 'getifaddrs'
          getifaddrs(&addrs);
          ^
  /home/project/src/jscam/JRTPLIB/src/rtpudpv4transmitter.cpp:1826:2: error: use of undeclared identifier 'freeifaddrs'
          freeifaddrs(addrs);
          ^
  2 errors generated.
  ninja: build stopped: subcommand failed.

Answer 1

Android NDK has <ifaddrs.h> for you. But the missing functions, like getifaddrs() , are available for __ANDROID_API__ 24 and higher, while your projects sets __ANDROID_API__=16 .

If your library will be used with minSdkVersion below 24, you cannot use these functions. Unfortunately, JRTPLIB doesn't seem to have such granular support for ifaddrs, but you can force RTP_SUPPORT_IFADDRS off if you choose to.