View source for Building LDC from source

This page shows you how to build and install [[LDC]] on most Posix-like systems such as linux, macOS, BSD, or Android. For building LDC on '''Windows''', please see [[Building and hacking LDC on Windows using MSVC|its dedicated page]].

== Advice ==
It is hard for us to keep these wiki pages up-to-date. If you run into trouble, have a look at the build scripts for our [http://wiki.dlang.org/LDC_contributor%27s_guide#Continuous_Integration Continuous Integration] platforms: the Azure Pipelines scripts for [https://github.com/ldc-developers/ldc/blob/master/.azure-pipelines/posix.yml Ubuntu Linux and macOS] and [https://github.com/ldc-developers/ldc/blob/master/.azure-pipelines/windows.yml Windows] are always up-to-date with the latest build setup.

== Prerequisites ==

* Git (for fetching the source code, if not using a tarball)
* a C++ toolchain (GCC, Clang, …)
* a D compiler (LDC/DMD/GDC)
** If there's no suitable prebuilt D compiler for your platform: LDC 0.17 is the last version that does not need a D compiler to be built. Thus for bootstrapping, you can first build 0.17, and then use that to build newer compiler versions. Our testing infrastructure explicitly tests that new LDC versions can be built with 0.17 (on 64-bit systems). The git branch is called <tt>ltsmaster</tt> or [https://github.com/ldc-developers/ldc/releases you can get the source for the latest 0.17 release]. Note that it doesn't support the latest LLVM versions.
* CMake 3.8+
* [https://github.com/ninja-build/ninja/releases Ninja] or Make (Ninja is highly recommended as it builds in parallel by default and doesn't suffer from concurrency issues wrt. CMake custom commands)
* Python
* libcurl for Phobos' <tt>std.net.curl</tt> (e.g., <tt>libcurl4</tt> on recent Ubuntu)
* zlib-dev (e.g., <tt>zlib1g-dev</tt> on Ubuntu)
* For 0.17 ltsmaster:
** libconfig++: get the <tt>libconfig-devel</tt> or <tt>libconfig-dev</tt> package for some Linux distributions. On OSX, <tt>sudo port install libconfig-hr</tt>; on Android with the Termux app, <tt>pkg install libconfig-dev</tt>.
** libcurl-dev (e.g., <tt>libcurl4-gnutls-dev</tt> on Ubuntu)
* For the tests: gdb, unzip, zip and tzdata
** For BSD: bash and GNU make

On Ubuntu 18.04, this amounts to:

<syntaxhighlight lang=bash>
apt-get install git-core g++ ldc cmake ninja-build zlib1g-dev libcurl4 \
                gdb unzip zip tzdata # only required for the tests
</syntaxhighlight>

=== LLVM ===

The minimum supported LLVM version as of October 2019 is 3.9. Many Linux distributions already provide recent LLVM dev packages, sometimes in the form of user-curated package repositories (PPA, …). If a recent LLVM package is available, you might prefer to use it, as LLVM is a rather big project to build, e.g., via <code>apt-get install llvm-dev libclang-common-<matching LLVM version>-dev</code> (the LLVM compiler-rt libraries aka <tt>libclang-common-*-dev</tt> are optional but recommended). Only the Android target requires building [https://github.com/ldc-developers/llvm/releases our lightly tweaked version of LLVM], which is what we'll use here. There are also pre-built binary tarballs of our tweaked LLVM at that link, but they don't always work in other build environments, so we lay out the steps below in case you can't use them.

==== Building LLVM from source ====

<syntaxhighlight lang=bash>
# Non-Apple platforms: install binutils-dev package required to generate the ld.gold LTO linker plugin
apt-get install binutils-dev

# Download & extract source tarball of our lightly tweaked LLVM
curl -OL https://github.com/ldc-developers/llvm/releases/download/ldc-v9.0.0/llvm-9.0.0.src.tar.xz
tar -xf llvm-9.0.0.src.tar.xz

# Generate Ninja build files; remove `-G Ninja` to use Make instead
mkdir build-llvm && cd build-llvm # using a fresh new build dir is highly recommended whenever re-invoking CMake
cmake -G Ninja ../llvm-9.0.0.src \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_INSTALL_PREFIX=$PWD/../install-llvm \
  -DLLVM_BINUTILS_INCDIR=/usr/include \ # non-Apple only: location of binutils-dev's plugin.h
  -DLLVM_TARGETS_TO_BUILD='AArch64;ARM;Mips;MSP430;NVPTX;PowerPC;RISCV;WebAssembly;X86' \ # defaults to `all` if not specified
  -DCOMPILER_RT_INCLUDE_TESTS=OFF \
  -DLLVM_INCLUDE_TESTS=OFF

# Build and install (to directory specified as CMAKE_INSTALL_PREFIX above)
ninja install # or `make -j$(nproc) install`
cd ..
</syntaxhighlight>

Check out the [http://llvm.org/docs/CMake.html#llvm-specific-variables LLVM CMake page] for more CMake variables.

If you are planning to work on LDC itself, we recommend <tt>-DCMAKE_BUILD_TYPE=RelWithDebInfo</tt> for the (huge!) LLVM debuginfos and <tt>-DLLVM_ENABLE_ASSERTIONS=ON</tt>. LLVM's assertions mode also controls LDC's assertions (in both C++ and D parts of LDC). A debug build of LLVM (<tt>-DCMAKE_BUILD_TYPE=Debug</tt>) leads to a ''heavy'' slowdown of LDC's compilation speed. LLVM's <tt>CMAKE_BUILD_TYPE</tt> also controls how the C++ parts of LDC are compiled (LDC inherits the C++ compiler flags used to build LLVM).

If you are building natively in Termux for Android, you'll want to specify a proper default triple like <tt>-DLLVM_DEFAULT_TARGET_TRIPLE=armv7a-unknown-linux-androideabi</tt>.

== Building LDC from source ==

Now that you're ready to build LDC from source, clone the [https://github.com/ldc-developers/ldc LDC GitHub repository] or get [https://github.com/ldc-developers/ldc/releases one of our official source releases]:

 git clone --recursive https://github.com/ldc-developers/ldc.git

If you already have the git repo, don't forget to make sure your submodules are up to date by running <tt>git submodule update --init</tt>.

Run the following commands to configure and build LDC and its default libraries:

<syntaxhighlight lang=bash>
# Generate Ninja build files
mkdir build-ldc && cd build-ldc # using a fresh new build dir is highly recommended whenever re-invoking CMake
cmake -G Ninja ../ldc \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_INSTALL_PREFIX=$PWD/../install-ldc \
  -DLLVM_ROOT_DIR=$PWD/../install-llvm \                  # not needed if using a distro LLVM package
  -DD_COMPILER=$PWD/../ldc2-1.17.0-linux-x86_64/bin/ldmd2 # not needed if host D compiler (ldmd2/dmd/gdmd) is found in PATH or if building 0.17 ltsmaster

# Build; use -j<N> to limit parallelism if running out of memory. The binaries end up in bin/.
ninja
# Optional: install LDC to the CMAKE_INSTALL_PREFIX directory above
ninja install
</syntaxhighlight>

If you are planning to work on LDC, we recommend <tt>-DCMAKE_BUILD_TYPE=RelWithDebInfo</tt>.

If you want to target Android and are building ldc 1.4 or later, add <tt>-DLDC_TARGET_PRESET=Android-arm</tt> to the CMake config.

'''Note''': When installing LDC, existing Phobos/druntime includes (*.d and *.di files) aren't removed, only overwritten. This can cause conflicts when installing a new LDC version into an older LDC installation directory, e.g., when a <tt>std/datetime.d</tt> module is replaced by a <tt>std/datetime/*.d</tt> package. Cleaning up the installation dir or using a new one is recommended.

=== More useful CMake variables ===

{| class="wikitable"
|-
| '''LLVM_ROOT_DIR''' and '''LLVM_CONFIG''' || Allows you to specify the LLVM instance to use. LLVM_CONFIG specifies the path and name of the <tt>llvm-config</tt> binary to use. By default, it is assumed to be <tt>${LLVM_ROOT_DIR}/bin/llvm-config</tt>, otherwise it is searched for on default system paths.
|-
| '''BUILD_LTO_LIBS''' || Set this to <tt>ON</tt> to build an additional LTO-able set of Phobos and druntime (to be selected via <tt>-defaultlib=phobos2-ldc-lto,druntime-ldc-lto</tt>).
|-
| '''LDC_INSTALL_LTOPLUGIN''' || Set this to <tt>ON</tt> to include the LLVM <tt>ld.gold</tt> LTO linker plugin in the LDC installation, if found.
|-
| '''LDC_INSTALL_LLVM_RUNTIME_LIBS''' || Set this to <tt>ON</tt> to include the LLVM compiler-rt libraries in the LDC installation, if found.
|-
| '''MULTILIB''' || Set this to <tt>ON</tt> to build the 32-bit libraries too. You'll need a multilib C toolchain, e.g., <tt>apt-get install g++-multilib</tt>.
|-
| '''BUILD_SHARED_LIBS''' || Build only shared libraries (<tt>ON</tt>), only static libraries (<tt>OFF</tt>), or both (<tt>BOTH</tt>). Defaults to <tt>BOTH</tt> if shared libraries are supported on your platform, and <tt>OFF</tt> if they aren't.
|-
| '''LIB_SUFFIX''' || Some Linux distributions, such as Fedora, expect 64 bit libraries in <tt>/usr/lib64</tt> instead of <tt>/usr/lib</tt>. In this case, the installation directory can be adjusted using <tt>-DLIB_SUFFIX=64</tt>.
|-
| '''INCLUDE_INSTALL_DIR''' || The location the D modules for druntime and Phobos are installed to. Defaults to <tt>${CMAKE_INSTALL_PREFIX}/include/d</tt>.
|-
| '''LDC_WITH_LLD''' || Set this to <tt>OFF</tt> to disable the LLD linker integration even if the LLD headers are found, e.g., when getting errors about conflicting command-line options when running LDC.
|-
| '''LDC_DYNAMIC_COMPILE''' || Set this to <tt>False</tt> to disable dynamic compilation aka JIT. Try this when getting strange CMake errors.
|-
| '''LIBCONFIG_LIBRARY''' and '''LIBCONFIG_INCLUDE_DIR''' || Only for 0.17 ltsmaster, these variables can be used to specify the location of the libconfig++ library files and the path to the corresponding header files. NOTE: on error <tt>Could NOT find LibConfig (missing: LIBCONFIG_INCLUDE_DIR LIBCONFIG_LIBRARY)</tt> and using brew, use for eg: <tt>CMAKE_PREFIX_PATH=`brew --prefix` cmake …</tt> [see https://github.com/ldc-developers/ldc/issues/952].
|-
|}

NOTE: see https://github.com/Linuxbrew/homebrew-core/blob/master/Formula/ldc.rb for brew's install

== Tips ==

The Makefiles generated by CMake respect the <tt>DESTDIR</tt> variable for the <tt>install</tt> target. It is prepended to all the file installation targets. This can be useful for building packages:

<tt>$ make install DESTDIR=&lt;your root directory&gt;</tt>

[[Category:LDC]]