Main Content

AUTOSAR C++14 Rule M3-4-1

An identifier declared to be an object or type shall be defined in a block that minimizes its visibility

expand all in page

Description

Rule Definition

An identifier declared to be an object or type shall be defined in a block that minimizes its visibility.

Rationale

Defining variables with the minimum possible block scope reduces the possibility that they might later be accessed unintentionally.

For instance, if an object is meant to be accessed in one function only, declare the object local to the function.

Polyspace Implementation

The rule checker determines if an object is used in one block only. If the object is used in one block but defined outside the block, the checker raises a violation.

When you declare a variable outside a range-based for loop and use it only inside the loop block, Polyspace® flags the variable. If you cannot declare the variable inside the loop block, justify this result using comments in your result or code. See Address Results in Polyspace User Interface Through Bug Fixes or Justifications.

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

expand all

static int countReset; //Noncompliant

volatile int check;

void increaseCount() {
    int count = countReset;
    while(check%2) {
     count++;
    }
}

In this example, the variable countReset is declared global used in one function only. A compliant solution declares the variable local to the function to reduce its visibility.

Check Information

Group: Basic Concepts
Category: Required, Automated

Version History

Introduced in R2019a

expand all

See Also

Topics