String literal type is not as expected

Question

Consider the following program:

#include <iostream>
#include <type_traits>

int main(int argc, char* argv[])
{
    std::cout << std::is_same<decltype("hello"), char*>::value << std::endl;
    std::cout << std::is_same<decltype("hello"), const char*>::value << std::endl;
    std::cout << std::is_same<decltype("hello"), char[5]>::value << std::endl;
    std::cout << std::is_same<decltype("hello"), const char[5]>::value << std::endl;
    std::cout << std::is_same<decltype("hello"), char[6]>::value << std::endl;
    std::cout << std::is_same<decltype("hello"), const char[6]>::value << std::endl;
    std::cout << std::is_same<decltype("hello"), char[]>::value << std::endl;
    std::cout << std::is_same<decltype("hello"), const char[]>::value << std::endl;
    return 0;
}

It returns only zeroes, while I would have expected "hello" to be a const char[6]. What is the type of "hello"?

One could even read this as a dupe of https://stackoverflow.com/q/15036281/3002139 — Baum mit Augen, Feb 13 '18 at 22:33
Whenever you are wondering what `decltype(...)` is, it can be helpful to [get the compiler to tell you in an error message](https://wandbox.org/permlink/02pW8u0mTY9L57kS) — Justin, Feb 13 '18 at 22:34
How about const char (&)[6]? static_assert(std::is_same::value, "hrmm"); does not trigger using msvc17 with std set to latest. — SoronelHaetir, Feb 13 '18 at 22:41

Mateusz Grzejek · Accepted Answer · 2018-02-13T22:44:41.587

3

Edit: I was too quick and didn't notice the const char[6]. Since none of your checks involve &:

Quoting 8.4.1 Literals:

A literal is a primary expression. Its type depends on its form. A string literal is an lvalue; all other literals are prvalues.

Hence, the type is const char (&)[6].

edited Feb 13 '18 at 22:44

answered Feb 13 '18 at 22:33

Mateusz Grzejek

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It's type **is** `const char[6]`, the reference is the effect of `decltype`. Please check my duplicate link in question comment. – llllllllll Feb 13 '18 at 22:47

score 1 · Answer 2 · answered Feb 13 '18 at 22:36

1

Type is const char (&)[6] as you can see here

answered Feb 13 '18 at 22:36

Jarod42

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String literal type is not as expected

2 Answers2