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.
...
In this noncompliant code example, a decimal constant is mistakenly prefaced with zeros so that all the constants are a fixed length.:
Code Block | ||||
---|---|---|---|---|
| ||||
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.:
Code Block | ||||
---|---|---|---|---|
| ||||
i_array[0] = 2719; i_array[1] = 4435; i_array[2] = 42; |
...
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
Automated Detection
Tool | Version | Checker | Description | ||||||
Astrée |
| octal-constant | Fully checked | ||||||
Axivion Bauhaus Suite |
| CertC-DCL18 | |||||||
CodeSonar |
| LANG.TYPE.OC | Octal constant | ||||||
Helix QAC |
| C0339, C1272 | |||||||
Klocwork |
| MISRA.TOKEN.OCTAL.ESCAPE MISRA.TOKEN.OCTAL.INT | |||||||
LDRA tool suite |
| 83 S | Fully Implemented | ||||||
Parasoft C/C++test |
| CERT_C-DCL18-a | Octal and hexadecimal escape sequences shall be terminated |
Octal constants (other than zero) |
shall not be used |
...
PC-lint Plus |
| 9001 | Fully supported | ||||||
Polyspace Bug Finder |
| CERT C: Rec. DCL18-C | Checks for use of octal constants (rec. fully covered) | ||||||
PVS-Studio |
| V536 | |||||||
RuleChecker |
| octal-constant | Fully checked | ||||||
SonarQube C/C++ Plugin |
| OctalConstantAndSequence |
Related Guidelines
MISRA C:2012 | Rule 7.1 (required) |
...