.. _BuildingLibcxx: =============== Building libc++ =============== .. contents:: :local: .. _build instructions: Getting Started =============== On Mac OS 10.7 (Lion) and later, the easiest way to get this library is to install Xcode 4.2 or later. However if you want to install tip-of-trunk from here (getting the bleeding edge), read on. The following instructions describe how to checkout, build, test and (optionally) install libc++ and libc++abi. If your system already provides a libc++ installation it is important to be careful not to replace it. Remember Use the CMake option ``CMAKE_INSTALL_PREFIX`` to select a safe place to install libc++. .. warning:: * Replacing your systems libc++ installation could render the system non-functional. * macOS will not boot without a valid copy of ``libc++.1.dylib`` in ``/usr/lib``. .. code-block:: bash $ git clone https://github.com/llvm/llvm-project.git $ cd llvm-project $ mkdir build && cd build $ cmake -DCMAKE_C_COMPILER=clang \ -DCMAKE_CXX_COMPILER=clang++ \ -DLLVM_ENABLE_PROJECTS="libcxx;libcxxabi" \ ../llvm $ make # Build $ make check-cxx # Test $ make install-cxx install-cxxabi # Install For more information about configuring libc++ see :ref:`CMake Options`. You may also want to read the `LLVM getting started `_ documentation. Shared libraries for libc++ and libc++ abi should now be present in ``build/lib``. See :ref:`using an alternate libc++ installation ` for information on how to use this libc++. The instructions are for building libc++ on FreeBSD, Linux, or Mac using `libc++abi`_ as the C++ ABI library. On Linux, it is also possible to use :ref:`libsupc++ ` or libcxxrt. It is possible to build libc++ standalone (i.e. without building other LLVM projects). A standalone build would look like this: .. code-block:: bash $ git clone https://github.com/llvm/llvm-project.git llvm-project $ cd llvm-project $ mkdir build && cd build $ cmake -DCMAKE_C_COMPILER=clang \ -DCMAKE_CXX_COMPILER=clang++ \ -DLIBCXX_CXX_ABI=libcxxabi \ -DLIBCXX_CXX_ABI_INCLUDE_PATHS=path/to/separate/libcxxabi/include \ ../libcxx $ make $ make check-cxx # optional Experimental Support for Windows -------------------------------- The Windows support requires building with clang-cl as cl does not support one required extension: `#include_next`. Furthermore, VS 2015 or newer (19.00) is required. In the case of clang-cl, we need to specify the "MS Compatibility Version" as it defaults to 2014 (18.00). CMake + Visual Studio ~~~~~~~~~~~~~~~~~~~~~ Building with Visual Studio currently does not permit running tests. However, it is the simplest way to build. .. code-block:: batch > cmake -G "Visual Studio 14 2015" ^ -T "LLVM-vs2014" ^ -DLIBCXX_ENABLE_SHARED=YES ^ -DLIBCXX_ENABLE_STATIC=NO ^ -DLIBCXX_ENABLE_EXPERIMENTAL_LIBRARY=NO ^ \path\to\libcxx > cmake --build . CMake + ninja ~~~~~~~~~~~~~ Building with ninja is required for development to enable tests. Unfortunately, doing so requires additional configuration as we cannot just specify a toolset. .. code-block:: batch > cmake -G Ninja ^ -DCMAKE_MAKE_PROGRAM=/path/to/ninja ^ -DCMAKE_SYSTEM_NAME=Windows ^ -DCMAKE_C_COMPILER=clang-cl ^ -DCMAKE_C_FLAGS="-fms-compatibility-version=19.00 --target=i686--windows" ^ -DCMAKE_CXX_COMPILER=clang-cl ^ -DCMAKE_CXX_FLAGS="-fms-compatibility-version=19.00 --target=i686--windows" ^ -DLLVM_PATH=/path/to/llvm/tree ^ -DLIBCXX_ENABLE_SHARED=YES ^ -DLIBCXX_ENABLE_STATIC=NO ^ -DLIBCXX_ENABLE_EXPERIMENTAL_LIBRARY=NO ^ \path\to\libcxx > /path/to/ninja cxx > /path/to/ninja check-cxx Note that the paths specified with backward slashes must use the `\\` as the directory separator as clang-cl may otherwise parse the path as an argument. .. _`libc++abi`: http://libcxxabi.llvm.org/ .. _CMake Options: CMake Options ============= Here are some of the CMake variables that are used often, along with a brief explanation and LLVM-specific notes. For full documentation, check the CMake docs or execute ``cmake --help-variable VARIABLE_NAME``. **CMAKE_BUILD_TYPE**:STRING Sets the build type for ``make`` based generators. Possible values are Release, Debug, RelWithDebInfo and MinSizeRel. On systems like Visual Studio the user sets the build type with the IDE settings. **CMAKE_INSTALL_PREFIX**:PATH Path where LLVM will be installed if "make install" is invoked or the "INSTALL" target is built. **CMAKE_CXX_COMPILER**:STRING The C++ compiler to use when building and testing libc++. .. _libcxx-specific options: libc++ specific options ----------------------- .. option:: LIBCXX_INSTALL_LIBRARY:BOOL **Default**: ``ON`` Toggle the installation of the library portion of libc++. .. option:: LIBCXX_INSTALL_HEADERS:BOOL **Default**: ``ON`` Toggle the installation of the libc++ headers. .. option:: LIBCXX_ENABLE_ASSERTIONS:BOOL **Default**: ``OFF`` Build libc++ with assertions enabled. .. option:: LIBCXX_BUILD_32_BITS:BOOL **Default**: ``OFF`` Build libc++ as a 32 bit library. Also see `LLVM_BUILD_32_BITS`. .. option:: LIBCXX_ENABLE_SHARED:BOOL **Default**: ``ON`` Build libc++ as a shared library. Either `LIBCXX_ENABLE_SHARED` or `LIBCXX_ENABLE_STATIC` has to be enabled. .. option:: LIBCXX_ENABLE_STATIC:BOOL **Default**: ``ON`` Build libc++ as a static library. Either `LIBCXX_ENABLE_SHARED` or `LIBCXX_ENABLE_STATIC` has to be enabled. .. option:: LIBCXX_LIBDIR_SUFFIX:STRING Extra suffix to append to the directory where libraries are to be installed. This option overrides `LLVM_LIBDIR_SUFFIX`. .. option:: LIBCXX_INSTALL_PREFIX:STRING **Default**: ``""`` Define libc++ destination prefix. .. option:: LIBCXX_HERMETIC_STATIC_LIBRARY:BOOL **Default**: ``OFF`` Do not export any symbols from the static libc++ library. This is useful when the static libc++ library is being linked into shared libraries that may be used in with other shared libraries that use different C++ library. We want to avoid exporting any libc++ symbols in that case. .. option:: LIBCXX_ENABLE_FILESYSTEM:BOOL **Default**: ``ON`` except on Windows. This option can be used to enable or disable the filesystem components on platforms that may not support them. For example on Windows. .. _libc++experimental options: libc++experimental Specific Options ------------------------------------ .. option:: LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY:BOOL **Default**: ``ON`` Build and test libc++experimental.a. .. option:: LIBCXX_INSTALL_EXPERIMENTAL_LIBRARY:BOOL **Default**: ``LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY AND LIBCXX_INSTALL_LIBRARY`` Install libc++experimental.a alongside libc++. .. _ABI Library Specific Options: ABI Library Specific Options ---------------------------- .. option:: LIBCXX_CXX_ABI:STRING **Values**: ``none``, ``libcxxabi``, ``libcxxrt``, ``libstdc++``, ``libsupc++``. Select the ABI library to build libc++ against. .. option:: LIBCXX_CXX_ABI_INCLUDE_PATHS:PATHS Provide additional search paths for the ABI library headers. .. option:: LIBCXX_CXX_ABI_LIBRARY_PATH:PATH Provide the path to the ABI library that libc++ should link against. .. option:: LIBCXX_ENABLE_STATIC_ABI_LIBRARY:BOOL **Default**: ``OFF`` If this option is enabled, libc++ will try and link the selected ABI library statically. .. option:: LIBCXX_ENABLE_ABI_LINKER_SCRIPT:BOOL **Default**: ``ON`` by default on UNIX platforms other than Apple unless 'LIBCXX_ENABLE_STATIC_ABI_LIBRARY' is ON. Otherwise the default value is ``OFF``. This option generate and installs a linker script as ``libc++.so`` which links the correct ABI library. .. option:: LIBCXXABI_USE_LLVM_UNWINDER:BOOL **Default**: ``OFF`` Build and use the LLVM unwinder. Note: This option can only be used when libc++abi is the C++ ABI library used. libc++ Feature Options ---------------------- .. option:: LIBCXX_ENABLE_EXCEPTIONS:BOOL **Default**: ``ON`` Build libc++ with exception support. .. option:: LIBCXX_ENABLE_RTTI:BOOL **Default**: ``ON`` Build libc++ with run time type information. .. option:: LIBCXX_INCLUDE_TESTS:BOOL **Default**: ``ON`` (or value of ``LLVM_INCLUDE_DIR``) Build the libc++ tests. .. option:: LIBCXX_INCLUDE_BENCHMARKS:BOOL **Default**: ``ON`` Build the libc++ benchmark tests and the Google Benchmark library needed to support them. .. option:: LIBCXX_BENCHMARK_TEST_ARGS:STRING **Default**: ``--benchmark_min_time=0.01`` A semicolon list of arguments to pass when running the libc++ benchmarks using the ``check-cxx-benchmarks`` rule. By default we run the benchmarks for a very short amount of time, since the primary use of ``check-cxx-benchmarks`` is to get test and sanitizer coverage, not to get accurate measurements. .. option:: LIBCXX_BENCHMARK_NATIVE_STDLIB:STRING **Default**:: ``""`` **Values**:: ``libc++``, ``libstdc++`` Build the libc++ benchmark tests and Google Benchmark library against the specified standard library on the platform. On Linux this can be used to compare libc++ to libstdc++ by building the benchmark tests against both standard libraries. .. option:: LIBCXX_BENCHMARK_NATIVE_GCC_TOOLCHAIN:STRING Use the specified GCC toolchain and standard library when building the native stdlib benchmark tests. .. option:: LIBCXX_HIDE_FROM_ABI_PER_TU_BY_DEFAULT:BOOL **Default**: ``OFF`` Pick the default for whether to constrain ABI-unstable symbols to each individual translation unit. This setting controls whether `_LIBCPP_HIDE_FROM_ABI_PER_TU_BY_DEFAULT` is defined by default -- see the documentation of that macro for details. libc++ ABI Feature Options -------------------------- The following options allow building libc++ for a different ABI version. .. option:: LIBCXX_ABI_VERSION:STRING **Default**: ``1`` Defines the target ABI version of libc++. .. option:: LIBCXX_ABI_UNSTABLE:BOOL **Default**: ``OFF`` Build the "unstable" ABI version of libc++. Includes all ABI changing features on top of the current stable version. .. option:: LIBCXX_ABI_NAMESPACE:STRING **Default**: ``__n`` where ``n`` is the current ABI version. This option defines the name of the inline ABI versioning namespace. It can be used for building custom versions of libc++ with unique symbol names in order to prevent conflicts or ODR issues with other libc++ versions. .. warning:: When providing a custom namespace, it's the users responsibility to ensure the name won't cause conflicts with other names defined by libc++, both now and in the future. In particular, inline namespaces of the form ``__[0-9]+`` are strictly reserved by libc++ and may not be used by users. Doing otherwise could cause conflicts and hinder libc++ ABI evolution. .. option:: LIBCXX_ABI_DEFINES:STRING **Default**: ``""`` A semicolon-separated list of ABI macros to persist in the site config header. See ``include/__config`` for the list of ABI macros. .. _LLVM-specific variables: LLVM-specific options --------------------- .. option:: LLVM_LIBDIR_SUFFIX:STRING Extra suffix to append to the directory where libraries are to be installed. On a 64-bit architecture, one could use ``-DLLVM_LIBDIR_SUFFIX=64`` to install libraries to ``/usr/lib64``. .. option:: LLVM_BUILD_32_BITS:BOOL Build 32-bits executables and libraries on 64-bits systems. This option is available only on some 64-bits Unix systems. Defaults to OFF. .. option:: LLVM_LIT_ARGS:STRING Arguments given to lit. ``make check`` and ``make clang-test`` are affected. By default, ``'-sv --no-progress-bar'`` on Visual C++ and Xcode, ``'-sv'`` on others. Using Alternate ABI libraries ============================= .. _libsupcxx: Using libsupc++ on Linux ------------------------ You will need libstdc++ in order to provide libsupc++. Figure out where the libsupc++ headers are on your system. On Ubuntu this is ``/usr/include/c++/`` and ``/usr/include/c++//`` You can also figure this out by running .. code-block:: bash $ echo | g++ -Wp,-v -x c++ - -fsyntax-only ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu" ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../x86_64-linux-gnu/include" #include "..." search starts here: #include <...> search starts here: /usr/include/c++/4.7 /usr/include/c++/4.7/x86_64-linux-gnu /usr/include/c++/4.7/backward /usr/lib/gcc/x86_64-linux-gnu/4.7/include /usr/local/include /usr/lib/gcc/x86_64-linux-gnu/4.7/include-fixed /usr/include/x86_64-linux-gnu /usr/include End of search list. Note that the first two entries happen to be what we are looking for. This may not be correct on other platforms. We can now run CMake: .. code-block:: bash $ CC=clang CXX=clang++ cmake -G "Unix Makefiles" \ -DLIBCXX_CXX_ABI=libstdc++ \ -DLIBCXX_CXX_ABI_INCLUDE_PATHS="/usr/include/c++/4.7/;/usr/include/c++/4.7/x86_64-linux-gnu/" \ -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr \ You can also substitute ``-DLIBCXX_CXX_ABI=libsupc++`` above, which will cause the library to be linked to libsupc++ instead of libstdc++, but this is only recommended if you know that you will never need to link against libstdc++ in the same executable as libc++. GCC ships libsupc++ separately but only as a static library. If a program also needs to link against libstdc++, it will provide its own copy of libsupc++ and this can lead to subtle problems. .. code-block:: bash $ make cxx $ make install You can now run clang with -stdlib=libc++. .. _libcxxrt_ref: Using libcxxrt on Linux ------------------------ You will need to keep the source tree of `libcxxrt`_ available on your build machine and your copy of the libcxxrt shared library must be placed where your linker will find it. We can now run CMake like: .. code-block:: bash $ CC=clang CXX=clang++ cmake -G "Unix Makefiles" \ -DLIBCXX_CXX_ABI=libcxxrt \ -DLIBCXX_CXX_ABI_INCLUDE_PATHS=path/to/libcxxrt-sources/src \ -DCMAKE_BUILD_TYPE=Release \ -DCMAKE_INSTALL_PREFIX=/usr \ $ make cxx $ make install Unfortunately you can't simply run clang with "-stdlib=libc++" at this point, as clang is set up to link for libc++ linked to libsupc++. To get around this you'll have to set up your linker yourself (or patch clang). For example, .. code-block:: bash $ clang++ -stdlib=libc++ helloworld.cpp \ -nodefaultlibs -lc++ -lcxxrt -lm -lc -lgcc_s -lgcc Alternately, you could just add libcxxrt to your libraries list, which in most situations will give the same result: .. code-block:: bash $ clang++ -stdlib=libc++ helloworld.cpp -lcxxrt .. _`libcxxrt`: https://github.com/pathscale/libcxxrt/ Using a local ABI library installation --------------------------------------- .. warning:: This is not recommended in almost all cases. These instructions should only be used when you can't install your ABI library. Normally you must link libc++ against a ABI shared library that the linker can find. If you want to build and test libc++ against an ABI library not in the linker's path you need to set ``-DLIBCXX_CXX_ABI_LIBRARY_PATH=/path/to/abi/lib`` when configuring CMake. An example build using libc++abi would look like: .. code-block:: bash $ CC=clang CXX=clang++ cmake \ -DLIBCXX_CXX_ABI=libc++abi \ -DLIBCXX_CXX_ABI_INCLUDE_PATHS="/path/to/libcxxabi/include" \ -DLIBCXX_CXX_ABI_LIBRARY_PATH="/path/to/libcxxabi-build/lib" \ path/to/libcxx $ make When testing libc++ LIT will automatically link against the proper ABI library.