CODEWITHSUNDEEP
c++c++20forwarding-referencedecltype-auto
nullptr
nullptr

Reputation: 353

why use universal reference to accept function result rather than decltype(auto)?

auto && result = foo();

vs

decltype(auto) result = foo();

the only difference is that when the return type of foo is not reference, the type of former is rvalue reference but the type of latter is not reference.

declare return int return int& return int&&
auto int int int
auto&& int&& int& int&&
decltype(auto) int int& int&&

Upvotes: 2

Views: 165

Answers (1)

Barry
Barry

Reputation: 303007

Consider:

constexpr auto f() -> /* #1 */  {
    /* #2 */ r = g();
    return r;
}

if g returns a prvalue (let's say int), then:

#1 #2 result
auto&& auto&& dangling reference
auto&& decltype(auto) dangling reference
decltype(auto) auto&& dangling reference
decltype(auto) decltype(auto) returns int

Upvotes: 4

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