# Extra Clang Tools 21.1.8 documentation

## clang-tidy - bugprone-string-constructor

# bugprone-string-constructor

Finds string constructors that are suspicious and probably errors.

A common mistake is to swap parameters to the ‘fill’ string-constructor.

Examples:

    std::string str('x', 50); // should be str(50, 'x')

Calling the string-literal constructor with a length bigger than the literal is suspicious and adds extra random characters to the string.

Examples:

    std::string("test", 200);   // Will include random characters after "test".
    std::string("test", 2, 5);  // Will include random characters after "st".
    std::string_view("test", 200);

Creating an empty string from constructors with parameters is considered suspicious. The programmer should use the empty constructor instead.

Examples:

    std::string("test", 0);   // Creation of an empty string.
    std::string("test", 1, 0);
    std::string_view("test", 0);

Passing an invalid first character position parameter to constructor will cause `std::out_of_range` exception at runtime.

Examples:

    std::string("test", -1, 10); // Negative first character position.
    std::string("test", 10, 10); // First character position is bigger than string literal character range".

## Options

WarnOnLargeLength

  When true, the check will warn on a string with a length greater than `LargeLengthThreshold`. Default is true.

LargeLengthThreshold

  An integer specifying the large length threshold. Default is 0x800000.

StringNames

  Default is ::std::basic_string;::std::basic_string_view.

  Semicolon-delimited list of class names to apply this check to. By default ::std::basic_string applies to `std::string` and `std::wstring`. Set to e.g. ::std::basic_string;llvm::StringRef;QString to perform this check on custom classes.