How to print __int128 in g++?

Question

I am using the GCC built-in type __int128 for a few things in my C++ program, nothing really significant, at least not enough to justify to use BigInt library o

Answer 1

The stock cout does not handle __int128, but you may extends it with your own function.

For starter, code something like this:

std::ostream& operator<<(std::ostream& os, __int128 t) {
    // TODO: Convert t to string
    return os << str;
}

There are many solution on SO to convert 128 bit number to string, I'll not repeat here.

About library compatibility in comment:

You only need to roll your own function if the standard library does not provide such handler. Once the library support the type, you should then see a conflict when building, something like [ note: built-in candidate operator<< ], go try that with int64_t.