tidy - performance-inefficient-string-concatenation — Extra Clang Tools 22.0.0git documentation (original) (raw)

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, forand for-range statements. Default is false.