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AUTOSAR C++14 Rule A5-1-3

Parameter list (possibly empty) shall be included in every lambda expression

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Description

Rule Definition

Parameter list (possibly empty) shall be included in every lambda expression.

Rationale

You do not have to include a parameter list in a lambda expression. For instance, this expression is syntactically valid and indicates a closure that can be called without parameters:

[&counter] {
   ++counter;
}
However, without the (), you or a reviewer might not recognize this as a function object. It is visually clearer to use the parameter list (...) even when the list is empty. For instance:
[&counter]() {
   ++counter;
}

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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#include <cstdint>

void func() {
    std::int32_t count = 0;
    
    auto lambda1 = [&count] {++count;}; //Noncompliant
    auto lambda2 = [&count] () { //Compliant
        ++count;
    };
}

The lambda expression assigned to lambda1 does not have a parameter list and violates the rule. The issue is fixed when the same lambda expression is assigned to lambda2.

Check Information

Group: Expressions
Category: Required, Automated

Version History

Introduced in R2019b

See Also

Topics