MISRA C++:2023 Rule 5.13.2

Octal escape sequences, hexadecimal escape sequences and universal character names shall be terminated

Since R2024b

Description

Rule Definition

Octal escape sequences, hexadecimal escape sequences and universal character names shall be terminated. ¹

Rationale

There is potential for confusion if an octal or hexadecimal escape sequence, or universal character name is followed by other characters. For example, the character constant '\x1f' consists of a single character, whereas the character constant '\x1g' consists of the two characters '\x1' and 'g'. The manner in which multicharacter constants are represented as integers is implementation-defined.

If every octal and hexadecimal escape sequence and universal character name in a character constant or string literal is terminated, you reduce potential confusion.

Polyspace Implementation

The rule checker reports violations when an escape sequence or universal character name is not terminated with the end-of-string literal or another escape sequence.

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

Compliant and Noncompliant Escape Sequences

In this example, the rule is violated when an escape sequence is not terminated with the end of string literal or another escape sequence.

const char * s1 = "\x41g";     // Noncompliant 
const char * s2 = "\x41" "g";  // Compliant - Terminated by end of literal
const char * s3 = "\x41\x67";  // Compliant - Terminated by another escape sequence

const char * c1 = "\1412";   //Noncompliant
const char * c2 = "\141\t";  //Compliant 
const char * string2 = "\u1234F600"; //Non-compliant

const char * string22 = "\U1234F600"; // Compliant - universal charcater sequence consists
                                      // of 8 digits and terminates with the end of literal

Check Information

Group: Lexical Conventions

Category: Required

Version History

Introduced in R2024b