There are some optional features that can be enabled during compilation that are intended to help with specific types of development work or introduce experimental features. Currently, the following build options are available:
-`ENABLE_UNDEFINED_SANITIZER`: builds in runtime checks for [undefined behavior](https://en.wikipedia.org/wiki/Undefined_behavior) (like null pointer dereferences and signed integer overflows) in Lagom and the SerenityOS userland.
-`UNDEFINED_BEHAVIOR_IS_FATAL`: makes all undefined behavior sanitizer errors non-recoverable. This option reduces the performance overhead of `ENABLE_UNDEFINED_SANITIZER`.
-`ENABLE_ALL_THE_DEBUG_MACROS`: used for checking whether debug code compiles on CI. This should not be set normally, as it clutters the console output and makes the system run very slowly. Instead, enable only the needed debug macros, as described below.
-`ENABLE_COMPILETIME_FORMAT_CHECK`: checks for the validity of `std::format`-style format string during compilation. Enabled by default.
-`INCLUDE_WASM_SPEC_TESTS`: downloads and includes the WebAssembly spec testsuite tests. In order to use this option, you will need to install `prettier` and `wabt`. wabt version 1.0.35 or higher is required to pre-process the WebAssembly spec testsuite.
-`SERENITY_CACHE_DIR`: sets the location of a shared cache of downloaded files. Should not need to be set manually unless managing a distribution package.
-`ENABLE_NETWORK_DOWNLOADS`: allows downloading files from the internet during the build. Default on, turning off enables offline builds. For offline builds, the structure of the SERENITY_CACHE_DIR must be set up the way that the build expects.
Many parts of the codebase have debug functionality, mostly consisting of additional messages printed to the debug console. This is done via the `<component_name>_DEBUG` macros, which can be enabled individually at build time. They are listed in [this file](../Meta/CMake/all_the_debug_macros.cmake).
To toggle or change a build option, see the [CMake Cache Manipulation](#cmake-cache-manipulation) section below.
## CMake Cache Manipulation
CMake caches variables and options in the binary directory. This allows a developer to tailor variables that are `set()` within the persistent configuration cache.
There are three main ways to manipulate the cache:
-`cmake path/to/binary/dir -DVAR_NAME=Value`
-`ccmake` (TUI interface)
-`cmake-gui`
Options can be set via the initial `cmake` invocation that creates the binary directory to set the initial cache for the binary directory.
Once the binary directory exists, any of the three options above can be used to change the value of cache variables.
For example, boolean options such as `ENABLE_<setting>` or `<component_name>_DEBUG` can be enabled with the value `ON` and disabled with `OFF`:
For more information on how the CMake cache works, see the CMake guide for [Running CMake](https://cmake.org/runningcmake/). Additional context is available in the CMake documentation for
[variables](https://cmake.org/cmake/help/latest/manual/cmake-language.7.html#variables) and [set()](https://cmake.org/cmake/help/latest/command/set.html#set-cache-entry).
For information on running host and target tests, see [Testing](Testing.md). The documentation there also contains useful information for debugging CI test failures.
Some OS distributions don't ship bleeding-edge clang-format binaries. Below are 2 options to acquire an updated clang-format tool, in order of preference:
1) If you have a Debian-based (apt-based) distribution, use the [LLVM apt repositories](https://apt.llvm.org) to install the latest release of clang-format.
2) Compile LLVM from source as described in the LLVM documentation [here](https://llvm.org/docs/GettingStarted.html#compiling-the-llvm-suite-source-code).
