MISRA C++:2023 Rule 5.13.7

String literals with different encoding prefixes shall not be concatenated

Since R2024b

Description

Rule Definition

String literals with different encoding prefixes shall not be concatenated.

Rationale

Narrow string literals are enclosed in double quotes without a prefix. Wide string literals are enclosed in double quotes with a prefix L outside the quotes. See string literals.

Concatenation of narrow and wide string literals can lead to undefined behavior.

Polyspace Implementation

The rule checker reports violations on concatenations of wide string literals and narrow string literals.

If you do not specify the encoding of a string, Polyspace^® assumes that the encoding of the string is UTF-8. Polyspace does not report a violation when you concatenate an explicitly UTF-8 string with a string that does not specify any encoding:

const char* myStr = u8R"#(My)#"   "String"; // No violation

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

expand all

Concatenation of Narrow and Wide String Literals

char array[] = "Hello" "World";
wchar_t w_array[] = L"Hello" L"World";
wchar_t mixed[] = "Hello" L"World"; //Noncompliant

In this example, in the initialization of the array mixed, the narrow string literal "Hello" is concatenated with the wide string literal L"World".

Check Information

Group: Lexical Conventions

Category: Required

Version History

Introduced in R2024b