A simple compile time random number generator for C++. (uses std::rotl (C++20), but can be easily replaced if needed)

rng.cpp

constexpr uint32_t hash(uint32_t in)
{
	constexpr uint32_t r[]{
		0xdf15236c, 0x16d16793, 0x3a697614, 0xe0fe08e4,
		0xa3a53275, 0xccc10ff9, 0xb92fae55, 0xecf491de,
		0x36e86773, 0x0ed24a6a, 0xd7153d80, 0x84adf386,
		0x17110e76, 0x6d411a6a, 0xcbd41fed, 0x4b1d6b30
	};
	uint32_t out{ in ^ r[in & 0xF] };
	out ^= std::rotl(in, 020) ^ r[(in >> 010) & 0xF];
	out ^= std::rotl(in, 010) ^ r[(in >> 020) & 0xF];
	out ^= std::rotr(in, 010) ^ r[(in >> 030) & 0xF];
	return out;
}

template <size_t N>
constexpr uint32_t hash(char const(&str)[N])
{
	uint32_t h{};
	for (uint32_t i{}; i < N; ++i)
		h ^= uint32_t(str[i]) << (i % 4 * 8);
	return hash(h);
}

template <size_t N>
constexpr uint32_t constexpr_rand_impl(char const(&file)[N], uint32_t line, uint32_t column = 0x8dc97987)
{
	return hash(hash(__TIME__) ^ hash(file) ^ hash(line) ^ hash(column));
}

#define RANDOM constexpr_rand_impl(__FILE__, __LINE__)

void test()
{

	constexpr auto r1 = RANDOM;
	constexpr auto r2 = RANDOM;
	constexpr auto r3 = RANDOM;
	constexpr auto r4 = RANDOM;

}

Thanks! I will definitely add an attribution.