返回数组与返回int64_t（C / C ++）

Question

Again and again I read that you can't return an array from a function (in C/C++), but if that's the case, how can an int64_t be returned from a function? Isn't int64_t just an array of long int ?

(Yes, I know you can return a pointer to the start of an array, but I'm talking about returning int[4] , not int* .)

Answer 1

Isn't int64_t just an array of long int?

No, int64_t is an alias to a scalar type (as opposed to an aggregate type like an array type), and usually it is an alias to long long type.

Of course this applies when int64_t is defined as exact-width integer types are optional in C.

Answer 2

You can actually return any type that isn't an array - for example, if you wish to return four int values, you can return a struct my_4ints { int x[4] };

But int64_t (on a 32-bit machine) is one 'item'. It happens to be returned as two register values, on x86, typically eax, edx. But that's still returning ONE value.

Answer 3

If you wrap your array in a struct, you can return it from a function. But it is to be avoided because the ABIs are not completely stable on these kind of thing (example: objects compiled with gcc 3.3 linked to objects compiled with gcc 3.4 on Solaris are not compatible and may crash in that case).