//

// 9.5.type.punning.cpp

// chapter 09 others

// modern c++ tutorial

//

// created by changkun at changkun.de

// https://github.com/changkun/modern-cpp-tutorial

//

#include <bit>

#include <cstdint>

#include <cstring>

#include <iostream>

int main() {

float f = 3.14f;

// Reinterpreting an object's bytes via a different type through a

// pointer/reference cast violates the strict-aliasing rule and is

// undefined behavior:

// std::uint32_t bad = *reinterpret_cast<std::uint32_t*>(&f); // UB

// Portable and always-valid approach (any standard): std::memcpy.

std::uint32_t bits;

std::memcpy(&bits, &f, sizeof bits);

// C++20: std::bit_cast does the same well-defined reinterpretation

// and is usable in constant expressions.

auto bits2 = std::bit_cast<std::uint32_t>(f);

std::cout << std::hex << bits << " == " << bits2 << std::dec

<< " : " << (bits == bits2) << "\n";

std::cout << "round-trip: " << std::bit_cast<float>(bits2) << "\n";

}