llvm-project/clang-tools-extra/docs/clang-tidy/checks/performance-unnecessary-copy-initialization.rst

.. title:: clang-tidy - performance-unnecessary-copy-initialization

performance-unnecessary-copy-initialization
===========================================

Finds local variable declarations that are initialized using the copy
constructor of a non-trivially-copyable type but it would suffice to obtain a
const reference.

The check is only applied if it is safe to replace the copy by a const
reference. This is the case when the variable is const qualified or when it is
only used as a const, i.e. only const methods or operators are invoked on it, or
it is used as const reference or value argument in constructors or function
calls.

Example:

.. code-block:: c++

  const string& constReference() {
  }
  void function() {
    // The warning will suggest making this a const reference.
    const string UnnecessaryCopy = constReference();
  }

  struct Foo {
    const string& name() const;
  }
  void Function(const Foo& foo) {
    // The warning will suggest making this a const reference.
    string UnnecessaryCopy = foo.name();
    UnnecessaryCopy.find("bar");
  }