Should I Use std::move When Returning Objects from Functions?

When to Employ std::move on Function Return Values

When returning an object from a function, consider using std::move if:

1. Avoiding Copy Operations:
When returning an lvalue object that would otherwise require a copy operation, using std::move prevents the unnecessary copy. However, this is only effective if NRVO (named return value optimization) is not applicable. NRVO allows the compiler to elide the copy operation in certain circumstances, rendering std::move superfluous.

2. Ensured Object Disposal:
An lvalue object designated for disposal can be returned using std::move to ensure that any references or pointers to it become invalid. Without std::move, the compiler may not recognize this intent, leaving the object accessible after the function call.

3. Specific Exceptions:
There are some exceptions where std::move should not be used:

• When the object is a by-value function parameter, as it is already an rvalue.
• When it is preferable to allow move elision, which is typically the case for inexpensive operations.

Simplified Rules for Non-Template Code:

For non-template code, the following simplified rules can be applied:

• Use std::move when the object is an lvalue and moving it is desired.
• Do not worry about NRVO or potential copy optimizations, as these are automatically handled.

By following these guidelines, you can effectively utilize std::move to optimize function return values and ensure the proper handling of lvalue objects.

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