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MISRA C++:2008 Rule 2-13-2

Octal constants (other than zero) and octal escape sequences (other than "\0") shall not be used

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Description

Rule Definition

Octal constants (other than zero) and octal escape sequences (other than "\0") shall not be used.

Rationale

Octal constants are denoted by a leading zero. A developer or code reviewer can mistake an octal constant as a decimal constant with a redundant leading zero.

Octal escape sequences beginning with \ can also cause confusion. Inadvertently introducing an 8 or 9 in the digit sequence after \ breaks the escape sequence and introduces a new digit. A developer or code reviewer can ignore this issue and continue to treat the escape sequence as one digit.

Polyspace Implementation

The rule checker reports violations on:

  • Constants beginning with a leading zero.

  • Escape sequences that begin with a \ followed by a zero.

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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void func(void) {
  int busData[6];
  
  busData[0] = 100;
  busData[1] = 108;
  busData[2] = 052;      //Noncompliant
  busData[3] = 071;      //Noncompliant
  busData[4] = '\109';   //Noncompliant
  busData[5] = '\100';   //Noncompliant

}

The checker flags all octal constants (other than zero) and all octal escape sequences (other than \0).

In this example:

  • The octal escape sequence contains the digit 9, which is not an octal digit. This escape sequence has implementation-defined behavior.

  • The octal escape sequence \100 represents the number 64, but the rule checker forbids this use.

Check Information

Group: Lexical Conventions
Category: Required

Version History

Introduced in R2013b

See Also

Topics