LDNS 1.7.1 and above leverage Travis CI to increase coverage of compilers and platforms. Compilers include Clang and GCC; while platforms include Android, iOS, Linux, and OS X on AMD64, Aarch64, PowerPC and s390x hardware.
Android is tested on armv7a, aarch64, x86 and x86_64. The Android recipes build and install OpenSSL, and then builds LDNS. The testing is tailored for Android NDK-r19 and above, and includes NDK-r20 and NDK-r21. Mips and Mips64 are not tested because they are no longer supported under current NDKs.
iOS is tested for iPhoneOS, WatchOS, AppleTVOS, iPhoneSimulator, AppleTVSimulator and WatchSimulator. The testing uses Xcode 10 on OS X 10.13.
The LDNS Travis configuration file .travis.yml does not use top-level keys like os: and compiler: so there is no matrix expansion. Instead LDNS specifies the exact job to run under the jobs: and include: keys.
A typical recipe tests Clang and GCC on various hardware. The hardware includes AMD64, Aarch64, PowerPC and s390x. PowerPC is a little-endian platform, and s390x is a big-endian platform. There are pairs of recipes that are similar to the following.
OS X provides a single recipe to test Clang. GCC is not tested because GCC is an alias for Clang.
Two sanitizer builds are tested using Clang and GCC, for a total of four builds. The first sanitizer is Undefined Behavior sanitizer (UBsan), and the second is Address sanitizer (Asan). The sanitizers are only run on AMD64 hardware. Note the environment includes UBSAN=yes or ASAN=yes for the sanitizer builds.
The recipes are similar to the following.
When the Travis script encounters a sanitizer it uses different CFLAGS and configuration string.
Travis tests Android builds for the armv7a, aarch64, x86 and x86_64 architectures. The builds are trickier than other builds for several reasons. The testing requires installation of the Android NDK and SDK, it requires a cross-compile, and requires OpenSSL prerequisites. The Android cross-compiles also require care to set the Autotools triplet, the OpenSSL triplet, the toolchain path, the tool variables, and the sysroot. The discussion below detail the steps of the Android recipes.
The first step sets environmental variables for the cross-compile using the Travis job. A typical job with variables is shown below.
The second step for Android is to set the environmental variables ANDROID_NDK_ROOT and ANDROID_SDK_ROOT. This is an important step because the NDK and SDK use the variables internally to locate their own tools. Also see Recommended NDK Directory? on the android-ndk mailing list. (Many folks miss this step, or use incorrect variables like ANDROID_NDK_HOME or ANDROID_SDK_HOME).
If you are working from a developer machine you probably already have the necessary tools installed. You should ensure ANDROID_NDK_ROOT and ANDROID_SDK_ROOT are set properly.
The second step installs tools needed for OpenSSL, Expat and LDNS. This step is handled in by the script contrib/android/install_tools.sh. The tools include curl, tar, zip, unzip and java.
The third step installs the NDK and SDK. This step is handled in by the script contrib/android/install_ndk.sh. The script uses ANDROID_NDK_ROOT and ANDROID_SDK_ROOT to place the NDK and SDK in the $HOME directory.
If you are working from a developer machine you probably already have a NDK and SDK installed.
The fourth step sets the Android cross-compile environment using the script contrib/android/setenv_android.sh. The script is sourced so the variables in the script are available to the calling shell. The script sets variables like CC, CXX, AS and AR; sets CFLAGS and CXXFLAGS; sets a sysroot so Android headers and libraries are found; and adds the path to the toolchain to PATH.
contrib/android/setenv_android.sh knows which toolchain and architecture to select by inspecting environmental variables set by Travis for the job. In particular, the variables ANDROID_CPU and ANDROID_API tell contrib/android/setenv_android.sh which tools and libraries to select.
The contrib/android/setenv_android.sh script specifies the tools in a case statement like the following. There is a case for each of the architectures armv7a, aarch64, x86 and x86_64.
The fifth step builds OpenSSL. OpenSSL is built for iOS using the scripts contrib/android/install_openssl.sh. The script downloads, configures and installs the latest release version of the OpenSSL libraries. OpenSSL is configured with --prefix="$ANDROID_PREFIX" so the headers are placed in $ANDROID_PREFIX/include directory, and the libraries are placed in the $ANDROID_PREFIX/lib directory.
ANDROID_PREFIX is the value $HOME/android$ANDROID_API-$ANDROID_CPU. The libraries will be installed in $HOME/android23-armv7a, $HOME/android23-aarch64, etc. For Autotools projects, the appropriate PKG_CONFIG_PATH is exported.
PKG_CONFIG_PATH is an important variable. It is the userland equivalent to sysroot, and allows Autotools to find non-system headers and libraries for an architecture. Typical PKG_CONFIG_PATH are $HOME/android23-armv7a/lib/pkgconfig and $HOME/android23-aarch64/lib/pkgconfig.
OpenSSL also uses a custom configuration file called 15-android.conf. It is a copy of the OpenSSL's project file and located at contrib/android/15-android.conf. The LDNS version is copied to the OpenSSL source files after unpacking the OpenSSL distribution. The LDNS version has legacy NDK support removed and some other fixes, like ANDROID_NDK_ROOT awareness. The changes mean LDNS's 15-android.conf will only work with LDNS, with NDK-r19 and above, and a properly set environment.
OpenSSL is configured with no-engine. If you want to include OpenSSL engines then edit contrib/android/install_openssl.sh and remove the config option.
Finally, once OpenSSL are built, then the Travis script configures and builds LDNS. The recipe looks as follows.
Travis only smoke tests an Android build using a compile, link and install. The self tests are not run. TODO: figure out how to fire up an emulator, push the tests to the device and run them.
contrib/android/setenv_android.sh uses specific flags for CFLAGS and CXXFLAGS. They are taken from ndk-build, so we consider them the official flag set. It is important to use the same flags across projects to avoid subtle problems due to mixing and matching different flags.
CXXFLAGS includes -fexceptions and -frtti because exceptions and runtime type info are disabled by default. CFLAGS include -funwind-tables and -fexceptions to ensure C++ exceptions pass through C code, if needed. Also see docs/CPLUSPLUS-SUPPORT.html in the NDK docs.
To inspect the flags used by ndk-build for a platform clone ASOP's ndk-samples and build the hello-jni project. Use the V=1 flag to see the full compiler output from ndk-build.
Travis tests iOS builds for the armv7a, armv7s and aarch64 architectures for iPhoneOS, AppleTVOS and WatchOS. iPhoneOS is tested using both 32-bit builds (iPhones) and 64-bit builds (iPads). Travis also tests compiles against the simulators. The builds are trickier than other builds for several reasons. The testing requires a cross-compile, and requires OpenSSL prerequisites. The iOS cross-compiles also require care to set the Autotools triplet, the OpenSSL triplet, the toolchain path, the tool variables, and the sysroot. The discussion below detail the steps of the iOS recipes.
The first step sets environmental variables for the cross-compile using the Travis job. A typical job with variables is shown below.
The second step installs tools needed for OpenSSL, Expat and LDNS. This step is handled in by the script contrib/ios/install_tools.sh. The tools include autotools, curl and perl. The installation happens at the before_script: stage of Travis.
The third step sets the iOS cross-compile environment using the script contrib/ios/setenv_ios.sh. The script is sourced so the variables in the script are available to the calling shell. The script sets variables like CC, CXX, AS and AR; sets CFLAGS and CXXFLAGS; sets a sysroot so iOS headers and libraries are found; and adds the path to the toolchain to PATH.
contrib/ios/setenv_ios.sh knows which toolchain and architecture to select by inspecting environmental variables set by Travis for the job. In particular, the variables IOS_SDK and IOS_CPU tell contrib/ios/setenv_ios.sh which tools and libraries to select.
The contrib/ios/setenv_ios.sh script specifies the tools to use during the cross-compile. For Apple SDKs, the tool names are the same as a desktop. There are no special prefixes for the mobile tools.
If you are working from a developer machine you probably already have the necessary tools installed.
The fourth step builds OpenSSL. OpenSSL is built for iOS using the scripts contrib/ios/install_openssl.sh. The script downloads, configures and installs the latest release version of the OpenSSL libraries. OpenSSL is configured with --prefix="$IOS_PREFIX" so the headers are placed in $IOS_PREFIX/include directory, and the libraries are placed in the $IOS_PREFIX/lib directory.
IOS_PREFIX is the value $HOME/$IOS_SDK-$IOS_CPU. The scheme handles both iOS SDKs and cpu architectures so the pair receives a unique installation directory. The libraries will be installed in $HOME/iPhoneOS-armv7s, $HOME/iPhoneOS-arm64, $HOME/iPhoneSimulator-i386, etc. For Autotools projects, the appropriate PKG_CONFIG_PATH is exported.
PKG_CONFIG_PATH is an important variable. It is the userland equivalent to sysroot, and allows Autotools to find non-system headers and libraries for an architecture. Typical PKG_CONFIG_PATH are $HOME/iPhoneOS-armv7s/lib/pkgconfig and $HOME/iPhoneOS-arm64/lib/pkgconfig.
OpenSSL also uses a custom configuration file called 15-ios.conf. It is a copy of the OpenSSL's project file and located at contrib/ios/15-ios.conf. The LDNS version is copied to the OpenSSL source files after unpacking the OpenSSL distribution. The changes mean LDNS's 15-ios.conf will only work with LDNS and a properly set environment.
OpenSSL is configured with no-engine. Engines require dynamic loading so engines are disabled permanently in 15-ios.conf.
Finally, once OpenSSL are built, then the Travis script configures and builds LDNS. The full recipe looks as follows.
Travis only smoke tests an iOS build using a compile, link and install. The self tests are not run. TODO: figure out how to fire up an simulator, push the tests to the device and run them.
contrib/ios/setenv_ios.sh uses specific flags for CFLAGS and CXXFLAGS. They are taken from Xcode, so we consider them the official flag set. It is important to use the same flags across projects to avoid subtle problems due to mixing and matching different flags.