# Extra Clang Tools 21.1.8 documentation

## clang-tidy - performance-inefficient-string-concatenation

# performance-inefficient-string-concatenation

This check warns about the performance overhead arising from concatenating strings using the `operator+`, for instance:

    std::string a("Foo"), b("Bar");
    a = a + b;

Instead of this structure you should use `operator+=` or `std::string`’s (`std::basic_string`) class member function `append()`. For instance:

    std::string a("Foo"), b("Baz");
    for (int i = 0; i < 20000; ++i) {
        a = a + "Bar" + b;
    }

Could be rewritten in a greatly more efficient way like:

    std::string a("Foo"), b("Baz");
    for (int i = 0; i < 20000; ++i) {
        a.append("Bar").append(b);
    }

And this can be rewritten too:

    void f(const std::string&) {}
    std::string a("Foo"), b("Baz");
    void g() {
        f(a + "Bar" + b);
    }

In a slightly more efficient way like:

    void f(const std::string&) {}
    std::string a("Foo"), b("Baz");
    void g() {
        f(std::string(a).append("Bar").append(b));
    }

## Options

StrictMode

  When false, the check will only check the string usage in `while`, `for` and `for-range` statements. Default is false.