Bazel

Bazel is an open-source build and test automation tool developed by Google. It serves as a sophisticated build system capable of managing complex dependencies and ensuring reproducible builds.

In safety-critical development, particularly in automotive systems and other highly regulated industries, the integrity and reproducibility of the build process are essential. Bazel supports this by enforcing strict rules for how code is built (e.g., compiled, linked, packaged) and tested, thereby contributing indirectly to the overall safety assurance of the final product.

Bazel is highly versatile and can be used to build a wide range of software projects across various programming languages. Examples include client-server applications, programs designed for microcontrollers inside vehicles and other complex systems. Its architecture allows it to efficiently handle large, multi-language, and multi-platform projects.

This capability is especially valuable in the automotive industry, where modern vehicles integrate software from numerous domains often written in different languages, all requiring a consistent and reliable build process to ensure functional safety and regulatory compliance.

Although Bazel is not part of the final embedded product, its role in building safety-critical software makes it a key consideration.

The build system is responsible for transforming source code into final executable binaries. If Bazel introduces errors, omits dependencies, or selects wrong inputs, it could compromise the integrity of the safety-critical software. For instance, an incorrect build configuration could result in outdated code being linked into a safety-relevant module or unintended compiler flags being used, potentially introducing latent defects.

Under ISO 26262, Bazel is a critical part of the development lifecycle and must undergo thorough validation and verification to ensure the correctness and traceability of safety-critical software. Trust in the build artifacts depends directly on the reliability of the build system.

Bazel is a development tool used during the engineering lifecycle to manage and execute the build process. Its primary function is to generate executable code, libraries, and other artifacts that are eventually integrated into target hardware, such as an automotive electronic control unit (ECU).

Like compilers and linkers, Bazel contributes to the creation of the final product but does not reside or execute on the embedded system itself. However, the outputs it produces (compiled and linked software components) are integral to the final product. Therefore, the robustness and correctness of Bazel’s operation are indirectly critical to the functional safety of the overall system.

Bazel’s capabilities for producing reproducible and robust builds make it relevant to functional safety standards beyond the automotive domain.

In industries governed by standards such as IEC 61508 (industrial), DO-178C (aerospace), or EN 50128 (railway), ensuring the integrity of the software build process is a fundamental requirement. While these standards typically focus on qualifying tools that directly generate or verify safety-critical code, a reliable and well-controlled build system like Bazel significantly enhances confidence in software correctness and traceability. Its ability to manage complex dependencies, enforce build rules, and support continuous integration and delivery pipelines is invaluable for maintaining the strict configuration control and verification activities required by these rigorous safety frameworks.

Bazel’s reproducibility helps demonstrate that the delivered software was built exactly as intended—an essential factor for certification and audit processes across safety-critical domains.

Validas AG offers the Bazel QKit, a powerful solution for qualifying your Bazel instance in compliance with the ISO 26262 safety standard. This qualification ensures that safety-relevant Bazel functionalities are safe for use in your environment. Validas not only delivers the tools for qualification but also provides continuous support to maintain the safety of your Bazel instance after updates. Additionally, Validas offers a suite of safety-qualified tools that can be seamlessly integrated with Bazel to enhance your development workflow.