Value class of const int captured by lambda

Question

I am trying to understand when and when not a lambda with a fixed value-odr-uses a variable with automatic storage duration defined in its environment (caused by this answer ). Studying around this, I came across a little curiosity. GCC and Clang apparently disagree with the category of id id values ​​in the following code:

 template <typename T> void assert_is_lvalue(const T&) {} template <typename T> void assert_is_lvalue(const T&&) = delete; int main() { const int n = 0; [=] { assert_is_lvalue(n); }; } 

Clang successfully compiles the code, but GCC does not ( error: use of deleted function ). Which one is correct? Or is it something that is not defined or defined by the implementation?

An object reference binding should use odr-use, and this is confirmed by removing the default lambda capture and observing that both compilers then complain that n cannot be implicitly captured without a default binding.

Marking the lambda as mutable does not make any noticeable difference in the output of the compilers.