Can you `= delete` a templated function on a second declaration?

Question

Consider the following code:

template <typename T> int foo();
template <typename T> int foo() = delete;

is this valid C++11?

• GCC (9.1) says: Yes!
• clang (8.0) says: No!
• nvcc (9.2) says: No!
• MSVC (19.20) says: Yes! _{(in C++14 mode, it doesn't support C++11.)}

... see it all on GodBolt.

so which compilers are right and which compilers are s@#$%e ? :-)

Answer 1

GCC和MSVC有一个错误。

[dcl.fct.def.delete]

4 ...删除的功能定义应为该功能的第一个声明，或者对于功能模板的显式专门化，应为该专门化的第一个声明...

我相信它也代表实例化的声明和定义。由于引用已删除的函数是一个硬错误，因此必须尽快将其声明为Deleted。