Check it out in the intro video

Logical Design

Folly is a collection of relatively independent components, some as simple as a few symbols. There is no restriction on internal dependencies, meaning that a given folly module may use any other folly components.

All symbols are defined in the top-level namespace folly, except of course macros. Macro names are ALL_UPPERCASE and should be prefixed with FOLLY_. Namespace folly defines other internal namespaces such as internal or detail. User code should not depend on symbols in those namespaces.

Folly has an experimental directory as well. This designation connotes primarily that we feel the API may change heavily over time. This code, typically, is still in heavy use and is well tested.

What’s in it?

Because of folly’s fairly flat structure, the best way to see what’s in it is to look at the headers in top level folly/ directory. You can also check the docs folder for documentation, starting with the overview.

Folly is published on GitHub at https://github.com/facebook/folly.

`getdeps.py`

This script is used by many of Meta’s OSS tools. It will download and build all of the necessary dependencies first, and will then invoke cmake etc to build folly. This will help ensure that you build with relevant versions of all of the dependent libraries, taking into account what versions are installed locally on your system.

It’s written in python so you’ll need python3.6 or later on your PATH. It works on Linux, macOS and Windows.

The settings for folly’s cmake build are held in its getdeps manifest build/fbcode_builder/manifests/folly, which you can edit locally if desired.

Run tests

By default getdeps.py will build the tests for folly. To run them:

cd folly
python3 ./build/fbcode_builder/getdeps.py --allow-system-packages test

`build.sh`/`build.bat` wrapper

build.sh can be used on Linux and MacOS, on Windows use the build.bat script instead. Its a wrapper around getdeps.py.

Build with cmake directly

If you don’t want to let getdeps invoke cmake for you then by default, building the tests is disabled as part of the CMake all target. To build the tests, specify -DBUILD_TESTS=ON to CMake at configure time.

NB if you want to invoke cmake again to iterate on a getdeps.py build, there is a helpful run_cmake.py script output in the scratch-path build directory. You can find the scratch build directory from logs or with python3 ./build/fbcode_builder/getdeps.py show-build-dir.

Running tests with ctests also works if you cd to the build dir, e.g. (cd $(python3 ./build/fbcode_builder/getdeps.py show-build-dir) && ctest)

Finding dependencies in non-default locations

If you have boost, gtest, or other dependencies installed in a non-default location, you can use the CMAKE_INCLUDE_PATH and CMAKE_LIBRARY_PATH variables to make CMAKE look also look for header files and libraries in non-standard locations. For example, to also search the directories /alt/include/path1 and /alt/include/path2 for header files and the directories /alt/lib/path1 and /alt/lib/path2 for libraries, you can invoke cmake as follows:

cmake \
  -DCMAKE_INCLUDE_PATH=/alt/include/path1:/alt/include/path2 \
  -DCMAKE_LIBRARY_PATH=/alt/lib/path1:/alt/lib/path2 ...

Ubuntu LTS, CentOS Stream, Fedora

Use the getdeps.py approach above. We test in CI on Ubuntu LTS, and occasionally on other distros.

If you find the set of system packages is not quite right for your chosen distro, you can specify distro version specific overrides in the dependency manifests (e.g. https://github.com/facebook/folly/blob/main/build/fbcode_builder/manifests/boost ). You could probably make it work on most recent Ubuntu/Debian or Fedora/Redhat derived distributions.

At time of writing (Dec 2021) there is a build break on GCC 11.x based systems in lang_badge_test. If you don’t need badge functionality you can work around by commenting it out from CMakeLists.txt (unfortunately fbthrift does need it)

Windows (Vcpkg)

Note that many tests are disabled for folly Windows builds, you can see them in the log from the cmake configure step, or by looking for WINDOWS_DISABLED in CMakeLists.txt

That said, getdeps.py builds work on Windows and are tested in CI.

If you prefer, you can try Vcpkg. folly is available in Vcpkg and releases may be built via vcpkg install folly:x64-windows.

You may also use vcpkg install folly:x64-windows --head to build against main.

macOS

getdeps.py builds work on macOS and are tested in CI, however if you prefer, you can try one of the macOS package managers

Homebrew

folly is available as a Formula and releases may be built via brew install folly.

You may also use folly/build/bootstrap-osx-homebrew.sh to build against main:

  ./folly/build/bootstrap-osx-homebrew.sh

This will create a build directory _build in the top-level.

MacPorts

Install the required packages from MacPorts:

  sudo port install \
    boost \
    cmake \
    gflags \
    git \
    google-glog \
    libevent \
    libtool \
    lz4 \
    lzma \
    openssl \
    snappy \
    xz \
    zlib

Download and install double-conversion:

  git clone https://github.com/google/double-conversion.git
  cd double-conversion
  cmake -DBUILD_SHARED_LIBS=ON .
  make
  sudo make install

Download and install folly with the parameters listed below:

  git clone https://github.com/facebook/folly.git
  cd folly
  mkdir _build
  cd _build
  cmake ..
  make
  sudo make install

Folly