Abstract:

This webinar introduces product developers to the Bazel build system for C++ projects, asserting its superiority over traditional tools like CMake and Makefiles for achieving maintainable, scalable, and multi-language builds. The session provides practical guidance on setting up a new C++ project, managing external dependencies hermetically through the Bazel Central Registry, and configuring a sysroot to ensure reproducible builds independent of the host machine. A core focus is placed on advanced workflows, including seamless IDE integration with clangd via a compilation database, cross-compilation to diverse target platforms (e.g., Linux ARM64), and packaging applications into OCI containers. The webinar also demonstrates how to streamline multi-platform builds using Bazel's "transitions" feature, enforce code quality with clang-tidy through the Aspect CLI, and automate BUILD file generation with Gazelle, while also addressing common Bazel workflow challenges and criticisms.

A Developer's Guide to C++ with Bazel

• 0:10 Intro & Why Bazel for C++: The webinar targets product developers, aiming to make Bazel approachable for C++ workflows, arguing it's a superior choice over traditional tools like Make/CMake due to better maintainability and reproducibility.
• 4:52 Hermetic Builds & Toolchains: Explains Bazel's core concept of hermetic builds, using managed toolchains (like LLVM/Clang) and sysroots to ensure consistent, reproducible outputs independent of the host system.
• 10:27 Project Setup with Aspect CLI: Demonstrates initializing a new C++ project using aspect init, which automatically configures toolchains and environment variables (direnv).
• 15:51 "Hello World" & Bazel's Declarative Approach: Shows how to create a simple hello.c and its cc_binary rule, illustrating Bazel's declarative style of defining build targets rather than directly invoking compilers.
• 26:13 Hermetic Dependency Management (libmagic): Details how to add third-party C++ libraries (e.g., libmagic) from the Bazel Central Registry (BCR) and statically link them, ensuring all developers use the exact same, hermetic version.
• 35:54 IDE Integration with clangd: Explains how to generate a compile_commands.json file using @hedron_compile_commands to enable advanced editor features like auto-completion, jump-to-definition, and clang-tidy warnings via the clangd language server.
• 43:51 Cross-Compilation to Linux ARM64: Demonstrates building a C++ application for a linux_aarch64 target platform from a macOS host, by configuring a specific sysroot that contains the target environment's headers and libraries.
• 49:46 Packaging into OCI Containers: Illustrates how to package the cross-compiled binary into a minimal distroless Docker container using rules_oci, showcasing a complete build-to-containerization workflow.
• 53:53 Simplified Multi-Platform Builds with Transitions: Introduces Bazel's "transitions" feature, which allows targets in BUILD files (e.g., platform_transition_binary) to declare their desired target platform, removing the need for explicit --platforms flags and enabling multi-architecture builds.
• 57:44 Linting with clang-tidy & Aspect CLI: Shows how clang-tidy is used for code quality checks, both within the editor and programmatically via the bazel lint command (from Aspect CLI), with potential integration into CI/CD workflows.
• 1:00:25 Automated BUILD File Generation (Gazelle): Briefly covers Gazelle, a tool that automatically generates and maintains BUILD files by analyzing source code and identifying #include statements and dependencies.
• 1:01:01 Q&A and Bazel Critiques: Addresses common Bazel topics such as bazel run's unpredictable working directory and the speaker's strong opinion on preferring Makefiles for task runners over bazel run. Also, briefly discusses improvements needed for Bazel's coverage system.