If you don’t need any of the fancy formatting options, writing your own << operator is trivial. Formally, I suspect that writing one for __int128_t would be considered undefined behavior, but practically, I think it would work, up until the library starts providing actual support for it (at which point, you’d retire your conversion operator). … Read more
For GCC before C23, a primitive 128-bit integer type is only ever available on 64-bit targets, so you need to check for availability even if you have already detected a recent GCC version. In theory gcc could support TImode integers on machines where it would take 4x 32-bit registers to hold one, but I don’t … Read more
It’s here in System.Numerics. “The BigInteger type is an immutable type that represents an arbitrarily large integer whose value in theory has no upper or lower bounds.” var i = System.Numerics.BigInteger.Parse(“10000000000000000000000000000000”);