CODEWITHSUNDEEP
c++c++11
user11584010
user11584010

Reputation:

What is the difference between int{10} and 10?

As the title, I have two expressions:

int&& a = const_cast<int&&>(int{10});
int&& a = const_cast<int&&>(10);

The first compiling passed, but second not. Why is this happening?

In my view, it's because 10 is a literal and int{10} is a unamed variable. Is it?

Upvotes: 8

Views: 237

Answers (1)

SergeyA
SergeyA

Reputation: 62603

The only reason why your first conversion passed is a bug in g++. Neither code is legal, and both clang and icc reject it.

They even give a good message:

error: the operand of a const_cast to an rvalue reference type cannot be a non-class prvalue

This does make sense, since both 10 and int{10} are prvalues, and you can not bind a reference directly to prvalue. Instead, when references are initialized, compiler materializes the temporary variable and binds a reference to it. However, there are no rules for materializing temporary variables for const_cast - so there is nothing to bind the reference to.

Upvotes: 6

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