MISRA C:2012 Rule 7.2

A “u” or “U” suffix shall be applied to all integer constants that are represented in an unsigned type

Description

Rule Definition

A “u” or “U” suffix shall be applied to all integer constants that are represented in an unsigned type.

Rationale

The signedness of a constant is determined from:

Value of the constant.
Base of the constant: octal, decimal or hexadecimal.
Size of the various types.
Any suffixes used.

Unless you use a suffix u or U, another developer looking at your code cannot determine easily whether a constant is signed or unsigned.

Troubleshooting

If you expect a rule violation but do not see it, refer to Diagnose Why Coding Standard Violations Do Not Appear as Expected.

Examples

expand all

Use Suffix to Specify Unsigned Type

const unsigned long C[] = {
	0x9421FFD0, /*Noncompliant*/
	0x5322E762, 
	0x80000000, /*Noncompliant*/
	0x7FFFFFFF,
	0x00000001,
	0x83241947, /*Noncompliant*/
	0x57112957,
	0x2640EA23
};

const unsigned long D[] = {
	0x9421FFD0U, /*Compliant*/
	0x80000000U, /*Compliant*/
	0x83241947U, /*Compliant*/
};

In this example, Polyspace^® flags the unsigned members of C. For instance, 0x9421FFD0 is an unsigned number in a 32 bit environment because it exceeds the capacity of a signed integer. Because the unsigned number lacks the suffix u or U, Polyspace flags it. In D, the unsigned numbers use the suffix and are not flagged.

Check Information

Group: Literals and Constants

Category: Required

AGC Category: Readability

Version History

Introduced in R2014b