问题
Is the following code legal?
struct BigInt {
uint64_t a : 128;
};
回答1:
A bitfield must fit within a single int, so you're out of luck unless int is 128 bits on your platform.
(You were also missing a ; at the end of the struct prior to the edit.)
回答2:
Not legal in standard C11 (on most platforms; in principle, an int might be 128 bits, but I never met a platform having that). Read n1570 (draft specification).
But on some platforms recent compilers (e.g. GCC 6) provide __int128 as an extension. You won't use that as a bitfield, but as some kind of integral type.
See also this answer to a related question.
来源：https://stackoverflow.com/questions/41267458/in-c-can-you-have-a-128-bit-bitfield