Clang (6.0) emits "ud2" instructions for both auto&& and const auto&. If the const auto& can bind directly to an r-value, this must mean Clang is wrong, or am I missing something? GCC on the other hand emits code for both functions, although with slight difference (I'm not skilled enough in assembler to analyze the GCC output in further detail) Code example: https://godbolt.org/g/7fjszE <https://godbolt.org/g/uNJoZB> /Viktor On Fri, Mar 23, 2018 at 1:06 PM Peter Dimov via Boost <boost@lists.boost.org> wrote:
Matt Calabrese wrote:
On Fri, Mar 23, 2018 at 12:01 PM, Peter Dimov via Boost <boost@lists.boost.org> wrote:
Interesting question. value() && returns T&&. The auto const& reference can't bind directly to T&&, because that's not an lvalue.
An lvalue-reference-to-const can bind to an rvalue (it's why you can pass an rvalue to a function that takes a "const T&").
You're right, it does bind directly. http://eel.is/c++draft/dcl.init.ref#5.3.1
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