Compiler

A compiler is a specialized software tool that translates human-readable source code (written in programming languages like C or C++) into machine-readable object code and executable binaries. This machine code is what the computer's processor can directly execute. In the context of functional safety, the compiler is the bridge between the high-level design and the low-level instructions that control a safety-critical system, such as those in an automotive ECU.

Compilers are essential for developing software across a wide range of complex, technology-driven systems such as automobiles, trains, robotics, and spacecraft. They are the link between the designed algorithms and the actual operation of the electronic control units (ECUs).

In automotive development, every line of code, every function, and every interaction must be precise and reliable to ensure the vehicle operates safely. If a compiler introduces an error during the translation process, it can lead to unpredictable or dangerous behavior in the final system. This is why the selection and careful consideration of compilers are so important for automotive applications, particularly in safety-critical contexts governed by standards like ISO 26262.

ISO 26262 mandates a systematic evaluation process that begins by classifying the tool based on its potential impact on the system. It then defines the required Tool Confidence Level (TCL) according to how critical the tool's role is in the safety development lifecycle.

If the compiler's output directly influences safety, it may require "qualification" to ensure it can be trusted. This rigorous approach ensures that the compiler used to generate the vehicle's software is reliable and does not introduce safety risks, ultimately contributing to the overall safety argument of the vehicle.

The same principle also applies to other safety standards, such as IEC 61508 for general industrial applications or DO-178C for aerospace.

Although the software tool itself is not part of the final embedded product, the output of the compiler (the binary code) absolutely becomes part of the final system. If the compiler misinterprets or incorrectly optimizes a section of code, the final system may behave unpredictably, which could result in a potentially hazardous failure.

This distinction is critical; the compiler's output directly influences the safety of the vehicle's systems. Therefore, the compiler itself must be rigorously evaluated and potentially also be qualified according to ISO 26262.

While other tools, such as static analyzers, also play a vital role in verification and do not produce outputs that are part of the final system, the direct output of a compiler into the vehicle's software necessitates a higher level of scrutiny for functional safety.