CertC-DCL18ΒΆ

Do not begin integer constants with 0 when specifying a decimal value

Required inputs: IR

The C Standard defines octal constants as a 0 followed by octal digits (0 1 2 3 4 5 6 7). Programming errors can occur when decimal values are mistakenly specified as octal constants.

Noncompliant Code Example

In this noncompliant code example, a decimal constant is mistakenly prefaced with zeros so that all the constants are a fixed length:

i_array[0] = 2719;
i_array[1] = 4435;
i_array[2] = 0042;

Although it may appear that i_array[2] is assigned the decimal value 42, it is actually assigned the decimal value 34.

Compliant Solution

To avoid using wrong values and to make the code more readable, do not preface constants with zeroes if the value is meant to be decimal:

i_array[0] = 2719;
i_array[1] = 4435;
i_array[2] =   42;
Risk Assessment

Misrepresenting decimal values as octal can lead to incorrect comparisons and assignments.

Rule Severity Likelihood Remediation Cost Priority Level
DCL18-C Low Unlikely Low P3 L3
Related Guidelines
MISRA C:2012 Rule 7.1 (required)
Excerpt from SEI CERT C Coding Standard: Rules for Developing Safe, Reliable, and Secure Systems (2016 Edition) and SEI CERT C Coding Standard [https://cmu-sei.github.io/secure-coding-standards/sei-cert-c-coding-standard/recommendations/declarations-and-initialization-dcl/dcl18-c], Copyright (C) 1995-2026 Carnegie Mellon University. See section 9.4. "3rd-Party Licenses" in the documentation for full details.

Possible Messages

Key

Text

Severity

Disabled

octal_literal

Use of octal literal.

None

False

Options