Code Review for Safety-Critical Systems in Industrial Automation: Why Precision Matters

Introduction

In industrial automation, software errors don’t just trigger bugs—they can shut down factories, cause equipment to malfunction, or put human lives at risk. That's why source code review services have evolved into mission-critical components of the development cycle in this domain. For manufacturers and system integrators working with programmable logic controllers (PLCs), supervisory control systems, or embedded firmware, thorough code review isn’t just good practice; it’s a legal, operational, and ethical imperative.

As industrial systems become increasingly software-driven, particularly in sectors such as oil and gas, automotive, and pharmaceuticals, the role of the code reviewer has expanded. Code review helps enforce compliance, reduce risk, and improve long-term maintainability in environments where reliability cannot be compromised.

The Industrial Context: When Code Errors Have Real-World Consequences

In web or app development, a software failure might cause downtime or inconvenience. In industrial environments, that same failure could cost millions of dollars or, worse, endanger human lives. Code drives everything from robotic arms on automotive assembly lines to temperature sensors in food manufacturing plants. The stakes are high.

Control logic often governs physical processes, including valve positions, conveyor motor states, and emergency shutdowns. A single incorrect boolean value or timing miscalculation can lead to:

• Machinery damage
• Production halts
• Safety incidents
• Regulatory violations

In this context, the importance of precise, verified, and reviewed code cannot be overstated.

Unique Challenges in Reviewing Code for Safety-Critical Systems

Reviewing industrial software involves complexities beyond typical application development. Let’s examine a few key differences:

Hardware Interdependence

Industrial software often interfaces directly with actuators, sensors, and hardware buses (CAN, Modbus, Profibus). Reviewers must understand not just the code but the behavior of the hardware it interacts with.

Real-Time Constraints

Real-time operating systems (RTOS) are common. Missing a timing window due to inefficient loops or memory leaks can cause system-wide failures.

Multi-Language Environments

Codebases frequently span C/C++, ladder logic, structured text (ST), and function block diagrams (FBD). Reviewers must be fluent in both low-level and high-level industrial languages.

Strict Compliance Requirements

Code must adhere to standards such as:

• IEC 61508 (Functional Safety)
• ISO 26262 (Automotive)
• IEC 61131-3 (PLC programming languages)

These standards impose architectural and verification demands that must be enforced at the code review level.

How Source Code Review Services Support Industrial Compliance

Outsourcing to professional source code review services gives organizations access to independent expertise, advanced review techniques, and domain-specific checklists. Unlike internal peer reviews, external providers bring objectivity and often better traceability—a crucial requirement in regulated environments.

Key Benefits:

• Gap analysis against industry-specific safety standards
• Independent validation to satisfy external auditors
• Structured documentation for safety certification
• Integration with safety lifecycle processes (e.g., V-model)

DevCom, for instance, specializes in adapting its code review frameworks to regulated industries, helping clients ensure that every logic path aligns with compliance targets and system behavior expectations.

Elements of an Effective Review Process in Industrial Projects

Safety-First Mindset

Code elegance takes a backseat to logical correctness. Reviewers must prioritize deterministic behavior, fail-safes, and system resilience.

Checklists and Protocols

Reviewers must assess logic using tailored checklists. Items often include:

• Correct state machine transitions
• Timeout and watchdog handling
• Signal noise filtering
• Emergency fallback logic

Augmented Manual Review

Manual reviews should be paired with tools like:

• Polyspace or LDRA for static analysis
• Codesys PLC Checker for IEC-61131 code validation
• Model-based simulation for functional verification

These help automate detection of unreachable code, memory leaks, and race conditions, enabling reviewers to focus on logic-level and safety concerns.

How Code Review Reduces Risk in Control Logic Deployment

Code review in industrial settings serves a broader purpose than simply catching syntax errors. It acts as a risk mitigation layer by:

• Validating real-time constraints
• Ensuring proper handling of edge-case conditions
• Detecting logic errors before HIL (hardware-in-the-loop) testing
• Identifying conflicts in concurrent task scheduling

Integration With Functional Safety Lifecycle

Code review is an essential part of the functional safety lifecycle, particularly in phases such as:

• Software Architecture Review
• Module-Level Implementation Verification
• System Validation

Reviewers Contribute to:

• Failure Mode and Effects Analysis (FMEA)
• Safety integrity level (SIL) assessments
• Verification traceability matrices

This tightly couples code quality with system safety—reviewers aren’t just developers; they’re safety gatekeepers.

What Makes Industrial Code Review Different

Let’s compare side-by-side:

Aspect	Traditional Code Review	Industrial Code Review
Focus	Readability, performance, security	Safety, determinism, fault tolerance
Toolchain	GitHub, ESLint, SonarQube	TIA Portal, Codesys, static analyzers
Stakeholders	Devs, testers	Engineers, auditors, safety experts
Risks	Bugs, rework	Equipment damage, human harm, legal issues
Review Complexity	Low to medium	Medium to very high

Best Practices for Reviewing Industrial Control Code

To maximize the impact of your review process:

1. Use a Domain-Specific Checklist

Don’t rely on generic style guides. Use checklists tailored to your industry (pharma, manufacturing, mining, etc.)

2. Perform Dual-Level Reviews

Have both a software engineer and an automation/control engineer review logic paths independently.

3. Maintain Review Logs for Auditing

Each review cycle should generate a signed document, including:

• Issues found
• Reviewer names
• Correction summaries
• Post-review test outcomes

4. Encourage Simulator-Based Validation

Encourage reviewers to use system simulators or test benches to validate logic dynamically, especially for mission-critical states.

The Future of Code Review in Industrial Automation

As industrial automation embraces AI and data-driven systems, code review is evolving:

AI-Enhanced Review

Tools like DeepCode and GitHub Copilot offer ML-powered review suggestions, but in safety-critical environments, human reviewers must still validate AI-generated logic for explainability and determinism.

Review of AI Agents

Industrial AI agents (e.g., for predictive maintenance) require reviewed fallback logic. If AI behavior fails, hardcoded deterministic code must take over safely—this needs rigorous review.

Integration Into DevSecOps

Industrial DevSecOps pipelines are beginning to incorporate automated code review steps as early as commit-time, improving traceability and time-to-certification.

Conclusion: Code Review as the Guardian of Safety and Uptime

Code review in industrial automation is not a technical ritual—it’s a business-critical process. From compliance to safety to long-term maintainability, it touches every layer of industrial software success. By partnering with providers of source code review services, companies gain not only access to advanced tools and checklists but also domain-specific expertise that ensures software is ready for real-world deployment.

DevCom continues to support industrial clients worldwide by delivering precision-focused code review tailored to high-stakes environments. Whether you’re modernizing legacy systems or building greenfield automation software, investing in thorough, compliant, and structured code review is the best way to ensure that what you ship is safe, scalable, and ready to meet the future.