hisl_0067: Protect against divide-by-zero calculations

R2026b

Protect the divisor from going to zero in divide operations to improve robustness of generated code

Usage: High-Integrity System Modeling

Guideline ID: hisl_0067

Rules

hisl_0067: Protect against divide-by-zero calculations
To support robustness of generated code, when performing divide operations, protect the divisor from going to zero. Rationale Improve code compliance of generated code. Verification Check for divide-by-zero calculations (Simulink Check) Example — Correct Graphical function to model divide-by-zero check. Example — Incorrect Division operation can result in a divide-by-zero scenario.

hisl_0067: Protect against divide-by-zero calculations

To support robustness of generated code, when performing divide operations, protect the divisor from going to zero.

Rationale

Improve code compliance of generated code.

Verification

Check for divide-by-zero calculations (Simulink Check)

Example — Correct

Graphical function to model divide-by-zero check.

Correct example of modeling to prevent divide-by-zero.

Example — Incorrect

Division operation can result in a divide-by-zero scenario.

Divide-by-zero exists in model example.

To prove that division-by-zero is not possible, perform a static analysis of the model.
If division-by-zero is possible, implement one of the following. Using more than one option can result in redundant protection operations:
- Execute the divide-by-zero Model Advisor check
- Modify the code generation process to use Code Replacement Libraries (CRLs)
- For integer-based operations, clear configuration parameter Remove code that protects against integer division arithmetic exceptions (Embedded Coder)
Using CRLs or clearing configuration parameter Remove code that protects against integer division arithmetic exceptions (Embedded Coder) protects division operations against divide-by-zero operations. However, this action does introduce additional computational and memory overhead, as well as the potential to introduce unreachable code.

IEC 61508-3, Table A.3 (3) 'Language subset'
IEC 61508-3, Table A.4 (3) 'Defensive programming'
IEC 62304, 5.5.3 - Software Unit acceptance criteria
ISO 26262-6, Table 1(b) 'Use of language subsets'
ISO 26262-6, Table 1(d) 'Use of defensive implementation techniques'
EN 50128, Table A.4 (11) 'Language Subset'
EN 50128, Table A.3 (1) 'Defensive Programming'
EN 50657, Table A.4 (11) 'Language Subset'
EN 50657, Table A.3 (1) 'Defensive Programming'
EN 50716, Table A.3 (1) 'Defensive Programming'
DO-331, Section MB.6.3.2.g 'Algorithms are accurate'
MISRA C:2012, Dir 4.1
MISRA C:2023, Dir 4.1

Introduced in R2021a

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The Industry Standards section has been updated to include EN 50657 references.

The Industry Standards section has been updated to include MISRA C:2023 references.