Alignment not supported?

[정인배(Inbae Jeong)]

I need to align a type for calling an external function.

How do I set the alignment for a type like the struct below?

struct my_arg {
int a;
alignas(32) int b;
};

I don't see any option for giving the alignment requirement to b.

Currently I make a large enough character array and manually
serialize/deserialize as if gcc would do with alignof and sizeof
operator (and with non-standard endianness macros), and it seems it's
working, but i really hope there is support for alignment. The code
gets uglier when the struct contains another struct in it so that i
don't think i can manage it if the struct changes.