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AUTOSAR C++14 Rule M5-0-4

An implicit integral conversion shall not change the signedness of the underlying type

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Description

Rule Definition

An implicit integral conversion shall not change the signedness of the underlying type.

Rationale

Some conversions from signed to unsigned data types can lead to implementation-defined behavior. You can see unexpected results from the conversion.

Polyspace Implementation

The checker flags implicit conversions from a signed to an unsigned integer data type or vice versa.

The checker assumes that ptrdiff_t is a signed integer.

Troubleshooting

If you expect a rule violation but Polyspace® does not report it, see Diagnose Why Coding Standard Violations Do Not Appear as Expected.

Examples

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typedef char int8_t;
typedef unsigned char uint8_t;

void func()
  {
    int8_t s8;
    uint8_t u8;

    s8 = u8; //Noncompliant
    u8 = s8 + u8; //Noncompliant
    u8 = static_cast< uint8_t > ( s8 ) + u8; //Compliant
}

In this example, the rule is violated when a variable with a variable with signed data type is implicitly converted to a variable with unsigned data type or vice versa. If the conversion is explicit, as in the preceding example, the rule violation does not occur.

Check Information

Group: Expressions
Category: Required, Automated

Version History

Introduced in R2019a

See Also

Topics