# Build Instructions

Source releases may be obtained from the releases page.

You may also build the latest development version by cloning the git repository.

The following instructions assume that you have obtained a copy of the source, either by unpacking a release archive or cloning the git repository, and that your initial working directory contains the source code. (For release archives, this includes descending into the top level `lcm-X.Y.Z` subdirectory.)

Regardless of platform, CMake 3.12 or later is required. Binaries may be obtained from https://cmake.org/download/. Sufficiently recent Linux distributions may provide a new enough CMake via their package managers but if they don’t it is often possible to use pip to get a more recent version.

Please note that these instructions refer to the latest release of LCM. As the build procedure may vary from release to release, if you are building an old release or the latest `master`, we recommend referring to the copy of this document (`docs/content/build-instructions.md`) found in your source distribution.

## CMake Overview

These instructions assume that you will build in a directory named `build` as a direct subdirectory of the source directory, and that you will use the default generator. CMake permits the build directory to be almost anywhere (although in-source builds are strongly discouraged), and supports multiple generators. To users familiar with CMake, we recommend using Ninja.

A detailed description of how to use CMake is not specific to LCM and is beyond the scope of these instructions.

## Ubuntu and Debian

Required packages:

- build-essential

- cmake

- libglib2.0-dev

Optional packages (e.g., for language-specific support or building documentation):

- default-jdk

- doxygen

- liblua5.3-dev

- lua5.3

- python3-dev

Python packages needed for building documentation:

- Sphinx

- myst-parser

- sphinx-rtd-theme

From a terminal, run the following commands.

    mkdir build
    cd build
    cmake ..
    make
    sudo make install

## OS X

There are several ways to build LCM on OS X, none of which are necessarily better than the others.

### Homebrew

Install Homebrew packages

    brew install glib pkg-config cmake

Install Java. Type `javac` in a terminal, then follow the instructions.

Download and build LCM.

    mkdir build
    cd build
    cmake ..
    make
    make install

## Windows

LCM is officially supported on MSYS2. There is some residual support for Visual Studio that is unmaintained. Please see WinSpecific/README.md for more information on building on Windows.

## Other / General

On other POSIX.1-2001 systems (e.g., other GNU/Linux distributions, FreeBSD, Solaris, etc.) the only major requirement is to install the GLib 2.x development files and CMake. If possible, a Java development kit and Python should also be installed. Then follow the same instructions as for Ubuntu / Debian.

## Post Install

### Linux

In the following, replace `$LCM_INSTALL_PREFIX` with the prefix to which LCM was installed (by default, `/usr/local`), and replace `$LCM_LIBRARY_DIR` with the location of the LCM library, `lcm.so` (e.g. `/usr/local/lib`).

Some Linux distributions, such as Arch, do not contain the default install location (`/usr/local/lib/`) in the `ld.so.conf` search path. In this case, or if you installed LCM to a different, non-standard prefix, you may wish to create a `ld.so.conf` file for lcm:

    echo $LCM_LIBRARY_DIR > /etc/ld.so.conf.d/lcm.conf

Python users may need to add the lcm install location to Python’s site packages search path using a .pth file:

    PYTHON_VERSION=$(python -c "import sys; print(\"%s.%s\" % sys.version_info[:2])")
    PYTHON_USER_SITE=$(python -m site --user-site)
    echo "$LCM_LIBRARY_DIR/python$PYTHON_VERSION/site-packages" > $PYTHON_USER_SITE/lcm.pth

Lua users may need to add to `LUA_CPATH`:

    LUA_VERSION=$(lua -e "print(string.sub(_VERSION, 5))")
    export LUA_CPATH=$LUA_CPATH:$LCM_LIBRARY_DIR/lua/$LUA_VERSION/?.so

If you install LCM to a non-standard location (i.e. other than the default `/usr/local`, other CMake projects using LCM may need help finding it. Although you can always point to the directory where `lcmConfig.cmake` is installed by manually setting `lcm_DIR`, it may be convenient to add the location to the default search paths:

    export CMAKE_PREFIX_PATH=$CMAKE_PREFIX_PATH:$LCM_INSTALL_PREFIX

In addition, `pkgconfig` can be configured to find lcm.pc:

    export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:$LCM_LIBRARY_DIR/pkgconfig