hisl_0001: Usage of Abs block

R2026b

Avoid unsupported data types and protect against integer overflow for the Abs block

Usage: High-Integrity System Modeling

Guideline ID: hisl_0001

Rules

hisl_0001: Usage of Abs block
A

To support robustness of generated code, when using the Abs block, avoid Boolean and unsigned data types as inputs to the Abs block.

Rationale

Support generation of traceable code.

Verification

Check usage of Abs blocks (Simulink Check)

Example — Correct

Signed integer input to the Abs block.

Simulink model with Constant block value -128 feeding an Abs block with Saturate on Integer Overflow on, producing output 127

Example — Incorrect

Unsigned integer input to the Abs block.

Simulink model with Constant block value -128 feeding an Abs block with Saturate on Integer Overflow off, producing output -128

B

To support robustness of generated code, when using the Abs block, select block parameter Saturate on integer overflow.

Rationale

Achieve consistent and expected behavior of model simulation and generated code.

Verification

Check usage of Abs blocks (Simulink Check)

Tips

  • The Abs block does not support Boolean data types. Specifying an unsigned input data type, might optimize the Abs block out of the generated code, resulting in a block you cannot trace to the generated code.

  • For signed data types, Simulink® does not represent the absolute value of the most negative value. When you select Saturate on integer overflow, the absolute value of the data type saturates to the most positive representable value. When you clear Saturate on integer overflow, absolute value calculations in the simulation and generated code might not be consistent or expected.

Industry Standards

  • IEC 61508-3, Table A.3 (3) 'Language subset'
    IEC 61508-3, Table A.4 (3) 'Defensive programming'
    IEC 61508-3, Table A.3 (2) 'Strongly typed programming language'
    IEC 61508-3, Table B.8 (3) 'Control Flow Analysis'

  • IEC 62304, 5.5.3 - Software Unit acceptance criteria

  • ISO 26262-6, Table 1 (1b) 'Use of language subsets'
    ISO 26262-6, Table 1 (1d) 'Use of defensive implementation techniques'
    ISO 26262-6, Table 7 (1f) 'Control flow analysis'

  • EN 50128, Table A.4 (11) 'Language Subset'
    EN 50128, Table A.3 (1) 'Defensive Programming'
    EN 50128, Table A.4 (8) 'Strongly Typed Programming Language'
    EN 50128 Table A.19 (3) 'Control Flow Analysis'

  • EN 50657, Table A.4 (11) 'Language Subset'
    EN 50657, Table A.3 (1) 'Defensive Programming'
    EN 50657, Table A.4 (8) 'Strongly Typed Programming Language'
    EN 50657 Table A.19 (3) 'Control Flow Analysis'

  • EN 50716, Table A.3 (1) 'Defensive Programming'
    EN 50716, Table A.19 (1) 'Control Flow Analysis'

  • DO-331, Section MB.6.3.2.d 'Low-level requirements are verifiable'
    DO-331, Section MB.6.3.2.g – 'Algorithms are accurate'

  • MISRA C:2012, Dir 4.1

  • MISRA C:2023, Dir 4.1

  • INT32-C. Ensure that operations on signed integers do not result in overflow

Version History

Introduced in R2010a

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