Attention: Here be dragons

This is the latest (unstable) version of this documentation, which may document features not available in or compatible with released stable versions of Redot.

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Introduction to the buildsystem

Redot is a primarily C++ project and it uses the SCons build system. We love SCons for how maintainable and easy to set up it makes our buildsystem. And thanks to that compiling Redot from source can be as simple as running:

scons

This produces an editor build for your current platform, operating system, and architecture. You can change what gets built by specifying a target, a platform, and/or an architecture. For example, to build an export template used for running exported games, you can run:

scons target=template_release

If you plan to debug or develop the engine, then you might want to enable the dev_build option to enable dev-only debugging code:

scons dev_build=yes

Following sections in the article will explain these and other universal options in more detail. But before you can compile Redot, you need to install a few prerequisites. Please refer to the platform documentation to learn more:

These articles cover in great detail both how to setup your environment to compile Redot on a specific platform, and how to compile for that platform. Please feel free to go back and forth between them and this article to reference platform-specific and universal configuration options.

Using multi-threading

The build process may take a while, depending on how powerful your system is. By default, Redot's SCons setup is configured to use all CPU threads but one (to keep the system responsive during compilation). If you want to adjust how many CPU threads SCons will use, use the -j <threads> parameter to specify how many threads will be used for the build.

Example for using 4 threads:

scons -j4

Platform selection

Redot's build system will begin by detecting the platforms it can build for. If not detected, the platform will simply not appear on the list of available platforms. The build requirements for each platform are described in the rest of this tutorial section.

SCons is invoked by just calling scons. If no platform is specified, SCons will detect the target platform automatically based on the host platform. It will then start building for the target platform right away.

To list the available target platforms, use scons platform=list:

scons platform=list
scons: Reading SConscript files ...
The following platforms are available:

    android
    javascript
    linuxbsd
    server
    windows

Please run SCons again and select a valid platform: platform=<string>

To build for a platform (for example, linuxbsd), run with the platform= (or p= to make it short) argument:

scons platform=linuxbsd

Resulting binary

The resulting binaries will be placed in the bin/ subdirectory, generally with this naming convention:

godot.<platform>.<target>[.dev][.double].<arch>[.<extra_suffix>][.<ext>]

For the previous build attempt, the result would look like this:

ls bin
bin/godot.linuxbsd.editor.x86_64

This means that the binary is for Linux or *BSD (not both), is not optimized, has the whole editor compiled in, and is meant for 64 bits.

A Windows binary with the same configuration will look like this:

C:\godot> dir bin/
godot.windows.editor.64.exe

Copy that binary to any location you like, as it contains the Project Manager, editor and all means to execute the game. However, it lacks the data to export it to the different platforms. For that the export templates are needed (which can be either downloaded from redotengine.org, or you can build them yourself).

Aside from that, there are a few standard options that can be set in all build targets, and which will be explained below.

Target

Target controls if the editor is contained and debug flags are used. All builds are optimized. Each mode means:

  • target=editor: Build with editor, optimized, with debugging code (defines: TOOLS_ENABLED, DEBUG_ENABLED, -O2//O2)

  • target=template_debug: Build with C++ debugging symbols (defines: DEBUG_ENABLED, -O2//O2)

  • target=template_release: Build without symbols (defines: -O3//O2)

The editor is enabled by default in all PC targets (Linux, Windows, macOS), disabled for everything else. Disabling the editor produces a binary that can run projects but does not include the editor or the Project Manager.

scons platform=<platform> target=editor/template_debug/template_release

Development and production aliases

When creating builds for development (running debugging/profiling tools), you often have different goals compared to production builds (making binaries as fast and small as possible).

Redot provides two aliases for this purpose:

  • dev_mode=yes is an alias for verbose=yes warnings=extra werror=yes tests=yes. This enables warnings-as-errors behavior (similar to Redot's continuous integration setup) and also builds unit tests so you can run them locally.

  • production=yes is an alias for use_static_cpp=yes debug_symbols=no lto=auto. Statically linking libstdc++ allows for better binary portability when compiling for Linux. This alias also enables link-time optimization when compiling for Linux, Web and Windows with MinGW, but keeps LTO disabled when compiling for macOS, iOS or Windows with MSVC. This is because LTO on those platforms is very slow to link or has issues with the generated code.

You can manually override options from those aliases by specifying them on the same command line with different values. For example, you can use scons production=yes debug_symbols=yes to create production-optimized binaries with debugging symbols included.

Dev build

Note

dev_build should not be confused with dev_mode, which is an alias for several development-related options (see above).

When doing engine development the dev_build option can be used together with target to enable dev-specific code. dev_build defines DEV_ENABLED, disables optimization (-O0//0d), enables generating debug symbols, and does not define NDEBUG (so assert() works in thirdparty libraries).

scons platform=<platform> dev_build=yes

This flag appends the .dev suffix (for development) to the generated binary name.

See also

There are additional SCons options to enable sanitizers, which are tools you can enable at compile-time to better debug certain engine issues. See Using sanitizers for more information.

Debugging symbols

By default, debug_symbols=no is used, which means no debugging symbols are included in compiled binaries. Use debug_symbols=yes to include debug symbols within compiled binaries, which allows debuggers and profilers to work correctly. Debugging symbols are also required for Redot's crash stacktraces to display with references to source code files and lines.

The downside is that debugging symbols are large files (significantly larger than the binaries themselves). As a result, official binaries currently do not include debugging symbols. This means you need to compile Redot yourself to have access to debugging symbols.

When using debug_symbols=yes, you can also use separate_debug_symbols=yes to put debug information in a separate file with a .debug suffix. This allows distributing both files independently. Note that on Windows, when compiling with MSVC, debugging information is always written to a separate .pdb file regardless of separate_debug_symbols.

Tip

Use the strip <path/to/binary> command to remove debugging symbols from a binary you've already compiled.

Optimization level

Several compiler optimization levels can be chosen from:

  • optimize=speed_trace (default when targeting non-Web platforms): Favors execution speed at the cost of larger binary size. Optimizations may sometimes negatively impact debugger usage (stack traces may be less accurate. If this occurs to you, use optimize=debug instead.

  • optimize=speed: Favors even more execution speed, at the cost of even larger binary size compared to optimize=speed_trace. Even less friendly to debugging compared to optimize=debug, as this uses the most aggressive optimizations available.

  • optimize=size (default when targeting the Web platform): Favors small binaries at the cost of slower execution speed.

  • optimize=debug: Only enables optimizations that do not impact debugging in any way. This results in faster binaries than optimize=none, but slower binaries than optimize=speed_trace.

  • optimize=none: Do not perform any optimization. This provides the fastest build times, but the slowest execution times.

  • optimize=custom (advanced users only): Do not pass optimization arguments to the C/C++ compilers. You will have to pass arguments manually using the cflags, ccflags and cxxflags SCons options.

Architecture

The arch option is meant to control the CPU or OS version intended to run the binaries. It is focused mostly on desktop platforms and ignored everywhere else.

Supported values for the arch option are auto, x86_32, x86_64, arm32, arm64, rv64, ppc32, ppc64 and wasm32.

scons platform=<platform> arch={auto|x86_32|x86_64|arm32|arm64|rv64|ppc32|ppc64|wasm32}

This flag appends the value of arch to resulting binaries when relevant. The default value arch=auto detects the architecture that matches the host platform.

Custom modules

It's possible to compile modules residing outside of Redot's directory tree, along with the built-in modules.

A custom_modules build option can be passed to the command line before compiling. The option represents a comma-separated list of directory paths containing a collection of independent C++ modules that can be seen as C++ packages, just like the built-in modules/ directory.

For instance, it's possible to provide both relative, absolute, and user directory paths containing such modules:

scons custom_modules="../modules,/abs/path/to/modules,~/src/redot_modules"

Note

If there's any custom module with the exact directory name as a built-in module, the engine will only compile the custom one. This logic can be used to override built-in module implementations.

See also

Custom modules in C++

Cleaning generated files

Sometimes, you may encounter an error due to generated files being present. You can remove them by using scons --clean <options>, where <options> is the list of build options you've used to build Redot previously.

Alternatively, you can use git clean -fixd which will clean build artifacts for all platforms and configurations. Beware, as this will remove all untracked and ignored files in the repository. Don't run this command if you have uncommitted work!

Other build options

There are several other build options that you can use to configure the way Redot should be built (compiler, debug options, etc.) as well as the features to include/disable.

Check the output of scons --help for details about each option for the version you are willing to compile.

Overriding the build options

Using a file

The default custom.py file can be created at the root of the Redot Engine source to initialize any SCons build options passed via the command line:

# custom.py

optimize = "size"
module_mono_enabled = "yes"
use_llvm = "yes"
extra_suffix = "game_title"

You can also disable some of the builtin modules before compiling, saving some time it takes to build the engine. See Optimizing a build for size page for more details.

See also

You can use the online Redot build options generator to generate a custom.py file containing SCons options. You can then save this file and place it at the root of your Redot source directory.

Another custom file can be specified explicitly with the profile command line option, both overriding the default build configuration:

scons profile=path/to/custom.py

Note

Build options set from the file can be overridden by the command line options.

It's also possible to override the options conditionally:

# custom.py

import version

# Override options specific for Redot 3.x and 4.x versions.
if version.major == 3:
    pass
elif version.major == 4:
    pass

Using the SCONSFLAGS

SCONSFLAGS is an environment variable which is used by the SCons to set the options automatically without having to supply them via the command line.

For instance, you may want to force a number of CPU threads with the aforementioned -j option for all future builds:

export SCONSFLAGS="-j4"

SCU (single compilation unit) build

Regular builds tend to be bottlenecked by including large numbers of headers in each compilation translation unit. Primarily to speed up development (rather than for production builds), Redot offers a "single compilation unit" build (aka "Unity / Jumbo" build).

For the folders accelerated by this option, multiple .cpp files are compiled in each translation unit, so headers can be shared between multiple files, which can dramatically decrease build times.

To perform an SCU build, use the scu_build=yes SCons option.

Note

When developing a Pull Request using SCU builds, be sure to make a regular build prior to submitting the PR. This is because SCU builds by nature include headers from earlier .cpp files in the translation unit, therefore won't catch all the includes you will need in a regular build. The CI will catch these errors, but it will usually be faster to catch them on a local build on your machine.

Export templates

Official export templates are downloaded from the Redot Engine site: redotengine.org. However, you might want to build them yourself (in case you want newer ones, you are using custom modules, or simply don't trust your own shadow).

If you download the official export templates package and unzip it, you will notice that most files are optimized binaries or packages for each platform:

android_debug.apk
android_release.apk
android_source.zip
ios.zip
linux_debug.arm32
linux_debug.arm64
linux_debug.x86_32
linux_debug.x86_64
linux_release.arm32
linux_release.arm64
linux_release.x86_32
linux_release.x86_64
macos.zip
version.txt
web_debug.zip
web_dlink_debug.zip
web_dlink_nothreads_debug.zip
web_dlink_nothreads_release.zip
web_dlink_release.zip
web_nothreads_debug.zip
web_nothreads_release.zip
web_release.zip
windows_debug_x86_32_console.exe
windows_debug_x86_32.exe
windows_debug_x86_64_console.exe
windows_debug_x86_64.exe
windows_debug_arm64_console.exe
windows_debug_arm64.exe
windows_release_x86_32_console.exe
windows_release_x86_32.exe
windows_release_x86_64_console.exe
windows_release_x86_64.exe
windows_release_arm64_console.exe
windows_release_arm64.exe

To create those yourself, follow the instructions detailed for each platform in this same tutorial section. Each platform explains how to create its own template.

The version.txt file should contain the corresponding Redot version identifier. This file is used to install export templates in a version-specific directory to avoid conflicts. For instance, if you are building export templates for Redot 3.1.1, version.txt should contain 3.1.1.stable on the first line (and nothing else). This version identifier is based on the major, minor, patch (if present) and status lines of the version.py file in the Redot Git repository.

If you are developing for multiple platforms, macOS is definitely the most convenient host platform for cross-compilation, since you can cross-compile for every target. Linux and Windows come in second place, but Linux has the advantage of being the easier platform to set this up.