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sccache - Shared Compilation Cache

sccache is a ccache-like compiler caching tool. It is used as a compiler wrapper and avoids compilation when possible, storing cached results either on local disk or in one of several cloud storage backends.

sccache includes support for caching the compilation of Assembler, C/C++ code, Rust, as well as NVIDIA's CUDA using nvcc, and clang, AMD's ROCm HIP.

sccache also provides icecream-style distributed compilation (automatic packaging of local toolchains) for all supported compilers (including Rust). The distributed compilation system includes several security features that icecream lacks such as authentication, transport layer encryption, and sandboxed compiler execution on build servers. See the distributed quickstart guide for more information.

sccache is also available as a GitHub Actions to facilitate the deployment using GitHub Actions cache.

Table of Contents (ToC)

Installation

There are prebuilt x86-64 binaries available for Windows, Linux (a portable binary compiled against musl), and macOS on the releases page. Several package managers also include sccache packages, you can install the latest release from source using cargo, or build directly from a source checkout.

macOS

On macOS sccache can be installed via Homebrew:

brew install sccache

or via MacPorts:

sudo port install sccache

Windows

On Windows, sccache can be installed via scoop:

scoop install sccache

or winget:

winget install Mozilla.sccache

Via cargo

If you have a Rust toolchain installed you can install sccache using cargo. Note that this will compile sccache from source which is fairly resource-intensive. For CI purposes you should use prebuilt binary packages.

cargo install sccache --locked

With Nix

Sccache is available in nixpkgs, so if you don't need the latest version you can use that:

buildInputs = [ pkgs.sccache ];

We also provide a flake with an overlay for getting the latest version:

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    sccache = {
      url = "github:mozilla/sccache";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = { self, nixpkgs, sccache, ... }:
    let
      system = "x86_64-linux";
      pkgs = import nixpkgs {
        inherit system;
        overlays = [ sccache.overlays.default ];
      };
    in {
      devShells.${system}.default = pkgs.mkShell {
        buildInputs = [ pkgs.sccache ];
      };
    };
}

Or use it directly from the flake without the overlay:

nix run github:mozilla/sccache -- --help
nix shell github:mozilla/sccache

Usage

Running sccache is like running ccache: prefix your compilation commands with it, like so:

sccache gcc -o foo.o -c foo.c

If you want to use sccache for caching Rust builds you can define build.rustc-wrapper in the cargo configuration file. For example, you can set it globally in $HOME/.cargo/config.toml by adding:

[build]
rustc-wrapper = "/path/to/sccache"

Note that you need to use cargo 1.40 or newer for this to work.

Alternatively you can use the environment variable RUSTC_WRAPPER:

export RUSTC_WRAPPER=/path/to/sccache
cargo build

sccache supports gcc, clang, MSVC, rustc, NVCC, NVC++, hipcc, and Wind River's diab compiler. Both gcc and msvc support Response Files, read more about their implementation here.

If you don't specify otherwise, sccache will use a local disk cache.

sccache works using a client-server model, where the server runs locally on the same machine as the client. The client-server model allows the server to be more efficient by keeping some state in memory. The sccache command will spawn a server process if one is not already running, or you can run sccache --start-server to start the background server process without performing any compilation.

By default sccache server will listen on 127.0.0.1:4226, you can specify environment variable SCCACHE_SERVER_PORT to use a different port or SCCACHE_SERVER_UDS to listen on unix domain socket. Abstract unix socket is also supported as long as the path is escaped following the format. For example:

% env SCCACHE_SERVER_UDS=$HOME/sccache.sock sccache --start-server # unix socket
% env SCCACHE_SERVER_UDS=\\x00sccache.sock sccache --start-server # abstract unix socket

You can run sccache --stop-server to terminate the server. It will also terminate after (by default) 10 minutes of inactivity.

Running sccache --show-stats will print a summary of cache statistics.

Some notes about using sccache with Jenkins are here.

To use sccache with cmake, provide the following command line arguments to cmake 3.4 or newer:

-DCMAKE_C_COMPILER_LAUNCHER=sccache
-DCMAKE_CXX_COMPILER_LAUNCHER=sccache

The process for using sccache with MSVC and cmake, depends on which version of cmake you're using. For versions of cmake 3.24 and earlier, to generate PDB files for debugging with MSVC, you can use the /Z7 option. Alternatively, the /Zi option together with /Fd can work if /Fd names a different PDB file name for each object file created. Note that CMake sets /Zi by default, so if you use CMake, you can use /Z7 by adding code like this in your CMakeLists.txt:

if(CMAKE_BUILD_TYPE STREQUAL "Debug")
  string(REPLACE "/Zi" "/Z7" CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG}")
  string(REPLACE "/Zi" "/Z7" CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG}")
elseif(CMAKE_BUILD_TYPE STREQUAL "Release")
  string(REPLACE "/Zi" "/Z7" CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE}")
  string(REPLACE "/Zi" "/Z7" CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE}")
elseif(CMAKE_BUILD_TYPE STREQUAL "RelWithDebInfo")
  string(REPLACE "/Zi" "/Z7" CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO}")
  string(REPLACE "/Zi" "/Z7" CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELWITHDEBINFO}")
endif()

By default, sccache will fail your build if it fails to successfully communicate with its associated server. To have sccache instead gracefully failover to the local compiler without stopping, set the environment variable SCCACHE_IGNORE_SERVER_IO_ERROR=1.

For versions of cmake 3.25 and later, to compile with MSVC, you have to use the new CMAKE_MSVC_DEBUG_INFORMATION_FORMAT option, meant to configure the -Z7 flag. Additionally, you must set the cmake policy number 0141 to the NEW setting:

set(CMAKE_MSVC_DEBUG_INFORMATION_FORMAT "$<$<CONFIG:Debug,RelWithDebInfo>:Embedded>")
cmake_policy(SET CMP0141 NEW)

Example configuration where we automatically look for sccache in the PATH:

find_program(SCCACHE sccache REQUIRED)

set(CMAKE_C_COMPILER_LAUNCHER ${SCCACHE})
set(CMAKE_CXX_COMPILER_LAUNCHER ${SCCACHE})
set(CMAKE_MSVC_DEBUG_INFORMATION_FORMAT "$<$<CONFIG:Debug,RelWithDebInfo>:Embedded>")
cmake_policy(SET CMP0141 NEW)

Alternatively, if configuring cmake with MSVC on the command line, assuming that sccache is on the default search path:

cmake -DCMAKE_C_COMPILER_LAUNCHER=sccache -DCMAKE_CXX_COMPILER_LAUNCHER=sccache -DCMAKE_MSVC_DEBUG_INFORMATION_FORMAT=Embedded -DCMAKE_POLICY_CMP0141=NEW [...]

And you can build code as usual without any additional flags in the command line, which is useful for I

Sccache

Install / Use

README