Question: I'm compiling the following program using Microsoft Visual C++, as a C++20 program:

```
#include <iostream>
#include <tuple>

int main()
{
    auto t1 = std::make_tuple("one", "two", "three");
    auto t2 = std::make_tuple("one", "two", "three");

    std::cout << "(t1 == t2) is " << std::boolalpha << (t1 == t2) << "\n";
    std::cout << "(t1 != t2) is " << std::boolalpha << (t1 != t2) << "\n";

    return 0;
}

```

When I run it, I see the following output:

```
(t1 == t2) is false
(t1 != t2) is true

```

The tuples are identical, so why does it have wrong comparison results? How do I fix this?

Answer: 
What is the type of `"one"`? This is not a string, but rather a string literal.

Your problem basically boils down to this code:

```
char const* a = "one";
char const* b = "one";

std::cout << "(a == b) is " << std::boolalpha << (a == b) << "\n";
std::cout << "(a != b) is " << std::boolalpha << (a != b) << "\n";

```

Which will most likely output the same result.

This is because a string literal will decay into a `char const*`. Comparing two pointer compares their location in memory. Now this is a matter of whether your compiler is folding string literals into one. If the string literals are folded, then they are gonna be equal, if they are not, they are not gonna be equal. This can vary with different optimization levels.

How can you fix your comparison then?

Preferably use `std::string_view` as you don't seem to need to own or change their content:

```
using namespace std::literals;

// ... 

auto t1 = std::make_tuple("one"sv, "two"sv, "three"sv);
auto t2 = std::make_tuple("one"sv, "two"sv, "three"sv);

```

The `std::string_view` class is a thin wrapper around a pointer and a size, and define a comparison operator that check for value equality.
The problem is unrelated to C++20, but comes from how string literals are implemented. The answer is for example here:

[Why do (only) some compilers use the same address for identical string literals?](https://stackoverflow.com/questions/52814457/why-do-only-some-compilers-use-the-same-address-for-identical-string-literals)

In short, your program falls into the category of "~~undefined~~ unspecified behavior", as it assumes that identical C-style string literals have identical addresses. This is because expressions like `"a" == "a"` compare addresses, not the content. Your code could be made safe and predictable if you used `std::string` literals, like `"one"s`, `"one"sv` etc., see <https://en.cppreference.com/w/cpp/string/basic_string/operator%22%22s>