tidy - cppcoreguidelines-rvalue-reference-param-not-moved — Extra Clang Tools 22.0.0git documentation (original) (raw)

Warns when an rvalue reference function parameter is never moved within the function body.

Rvalue reference parameters indicate a parameter that should be moved withstd::move from within the function body. Any such parameter that is never moved is confusing and potentially indicative of a buggy program.

Example:

void logic(std::string&& Input) { std::string Copy(Input); // Oops - forgot to std::move }

Note that parameters that are unused and marked as such will not be diagnosed.

Example:

void conditional_use([[maybe_unused]] std::string&& Input) { // No diagnostic here since Input is unused and marked as such }

Options¶

AllowPartialMove¶

If set to true, the check accepts std::move calls containing any subexpression containing the parameter. CppCoreGuideline F.18 officially mandates that the parameter itself must be moved. Default is false.

// 'p' is flagged by this check if and only if AllowPartialMove is false void move_members_of(pair<Obj, Obj>&& p) { pair<Obj, Obj> other; other.first = std::move(p.first); other.second = std::move(p.second); }

// 'p' is never flagged by this check void move_whole_pair(pair<Obj, Obj>&& p) { pair<Obj, Obj> other = std::move(p); }

IgnoreUnnamedParams¶

If set to true, the check ignores unnamed rvalue reference parameters. Default is false.

IgnoreNonDeducedTemplateTypes¶

If set to true, the check ignores non-deduced template type rvalue reference parameters. Default is false.

template struct SomeClass { // Below, 'T' is not deduced and 'T&&' is an rvalue reference type. // This will be flagged if and only if IgnoreNonDeducedTemplateTypes is // false. One suggested fix would be to specialize the class for 'T' and // 'T&' separately (e.g., see std::future), or allow only one of 'T' or // 'T&' instantiations of SomeClass (e.g., see std::optional). SomeClass(T&& t) { } };

// Never flagged, since 'T' is a forwarding reference in a deduced context template void forwarding_ref(T&& t) { T other = std::forward(t); }

MoveFunction¶

Specify the function used for moving. Default is ::std::move.

This check implements F.18from the C++ Core Guidelines.