This rule is part of MISRA C++:2023.
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Rule 5.13.3 - Octal constants shall not be used
Category: Required
Analysis: Decidable,Single Translation Unit
Rationale
Any integer constant beginning with a 0 (zero) is an octal constant. Because of this, a zero-prefixed constant that is intended to be
a decimal number may be interpreted as an octal number, contrary to developer expectations.
Note: this rule does not apply to octal escape sequences because the use of a leading \ character means that there is
less scope for confusion.
Exception
The integer constant 0 (written as a single numeric digit) is an octal constant, but its use is permitted as an exception to this
rule.
Example
code[ 1 ] = 109; // Compliant - decimal 109
code[ 2 ] = 100; // Compliant - decimal 100
code[ 3 ] = 052; // Non-compliant - equivalent to decimal 42, not 52
code[ 4 ] = 071; // Non-compliant - equivalent to decimal 57, not 71
code[ 5 ] = 0; // Compliant by exception
code[ 6 ] = 000; // Non-compliant - exception does not apply
code[ 7 ] = '\123'; // Rule does not apply
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