Passing c-style string to a template function

Question

I can't understand the following behavior of my program. As far as I know, template argument deduction allows only 1) array- or function-to-pointer conversions or 2) const conversions. The program below should result in a compilation error. However, if I pass two c-style strings of equal length, it compiles. What is causing this behavior?

#include <iostream>
#include <type_traits>
  
  
template <typename T>
int compare(T& x, T& y) {
  return 1;
}
  
  
int main() {
   compare("abc", "abc"); // no compilation error
}    

Answer 1

You can use cpp-insights to have a look at what is going on here. You will see your generated function signiture is:

template<>
int compare<const char[4]>(const char (&x)[4], const char (&y)[4])
{
  return 1;
}

This is because the type of the 2 literals are both const char[4] and you are taking a reference to them in your signature. The reason that it ends up being const& is because your type brings the const with it. The same way that this works:

template <typename T>
int foo(T& x) {
  return 1;
}

...

  int a = 5;
  const int& r_a = a;
  foo(r_a);