It's only for Linux 64-bit a 64-bit value. And it's seems a bit of a GCC choice, while Microsoft chose to keep long as a 32-bit integer (and not support long long for some time instead insisting in their _int64 private type).
And while not sure about the original Sun Solaris versions which might only have existed as 32-bit anyways, the later Linux kernel based versions however almost certainly use the same logic as the other Linux versions, although Sun had a tendency of trying to customize it when they could, and sometimes even when they shouldn't :-).