I noticed that
template <size_t n, char[n]> class x
{
};
is happily accepted by my C++ compiler. However, when I naively attempt something like
x <4, "hey"> something;
I get a nice
Non type template argument does not refer to any declaration
So I wonder: how would I go with actually making a class out of that template?
#include <iostream>
template <size_t n, char s[n]>
class X {
public:
X() {
std::cout << s;
std::cout << std::endl;
}
};
char hey[] = "hey";
int main() {
X<4, hey> x;
}
But X<4, "hey"> x; does not compile because, for a non-type template argument, certain restrictions apply:
For pointers to objects, the template arguments have to designate the address of an object with static storage duration and a linkage (either internal or external), or a constant expression that evaluates to the appropriate null pointer or std::nullptr_t value.
This raises another issue, I found the following on cppreference.com:
Array and function types may be written in a template declaration, but they are automatically replaced by pointer to object and pointer to function as appropriate.
So s is actually a pointer, therefore the following will compile:
X<5, hey> something;
Potential buffer-overflow problem.
X<"hey"> and char hey[] = "hey"; X<hey>. Is there any way to use a more compact notation, something similar to the "hey" version?
template <size_t n, char[n]> class x
{
};
char foobar[]="hey";
x<4, foobar> y;
Compiles with gcc 5.3.1
x<5, "hey"> something;, I don't think the compiler is going to enforce the type safety here.