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ladybird/Documentation/AdvancedBuildInstructions.md
Timothy Flynn a4e814578b Documentation: Add a note about clang plugins
2024-08-28 15:36:47 +02:00

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Advanced Build Instructions

This file covers a few advanced scenarios that go beyond what the basic build guide provides.

Ninja build targets

The Meta/ladybird.sh script provides an abstraction over the build targets which are made available by CMake. The following build targets cannot be accessed through the script and have to be used directly by changing the current directory to Build/ladybird and then running ninja <target>:

  • ninja check-style: Runs the same linters the CI does to verify project style on changed files
  • ninja lint-shell-scripts: Checks style of shell scripts in the source tree with shellcheck
  • ninja all_generated: Builds all generated code. Useful for running analysis tools that can use compile_commands.json without a full system build

CMake build options

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_ADDRESS_SANITIZER: builds in runtime checks for memory corruption bugs (like buffer overflows and memory leaks) in Lagom test cases.
  • ENABLE_MEMORY_SANITIZER: enables runtime checks for uninitialized memory accesses in Lagom test cases.
  • ENABLE_UNDEFINED_SANITIZER: builds in runtime checks for 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_COMPILER_EXPLORER_BUILD: Skip building non-library entities in Lagom (this only applies to Lagom).
  • ENABLE_FUZZERS: builds fuzzers for various parts of the system.
  • ENABLE_FUZZERS_LIBFUZZER: builds Clang libFuzzer-based fuzzers for various parts of the system.
  • ENABLE_FUZZERS_OSSFUZZ: builds OSS-Fuzz compatible fuzzers for various parts of the system.
  • 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.
  • LAGOM_TOOLS_ONLY: Skips building libraries, utiltis and tests for Lagom. Mostly only useful for cross-compilation.
  • 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.
  • INCLUDE_FLAC_SPEC_TESTS: downloads and includes the xiph.org FLAC test suite.
  • 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.
  • ENABLE_CLANG_PLUGINS: enables clang plugins which analyze the code for programming mistakes.

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.

To toggle or change a build option, see the 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:

# Reconfigure an existing binary directory with process debug enabled
$ cmake -B Build/ladbyird -DPROCESS_DEBUG=ON

For more information on how the CMake cache works, see the CMake guide for Running CMake. Additional context is available in the CMake documentation for variables and set().

Tests

For information on running host and target tests, see Running Tests. The documentation there also contains useful information for debugging CI test failures.

Clang-format updates

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 to install the latest release of clang-format.
  2. Compile LLVM from source as described in the LLVM documentation here.

Clangd Configuration

Clangd will automatically look for configuration information in files named .clangd in each of the parent directories of the file being edited. The Ladybird source code repository has a top-level .clangd configuration file in the root directory. One of the configuration stanzas in that file specifies the location for a compilation database. Depending on your build configuration (e.g., Debug, default, Sanitizer, etc), the path to the compilation database in that file may not be correct. The result is that clangd will have a difficult time understanding all your include directories. To resolve the problem, you can use the Meta/configure-clangd.sh script.

Clang Plugins

Clang plugins are used to validate the code at compile time. Currently, they are used to detect JavaScript-related garbage collection faux pas, such as neglecting to visit a garbage-collected type.

When clang plugins are enabled, it is recommended to have the following environment variable set for ccache:

export CCACHE_COMPILERCHECK="%compiler% -v"

By default, ccache will include the plugins themselves in file hashes. So if a plugin changes, the hash of every file will change, and you will be stuck with an uncached build. This setting will prevent ccache from using plugins in the file hashes.