Use alignas to align struct

Question

In the following struct:

struct alignas(?) test
{
    int32_t f1; // 4 bytes
    int8_t f2; // 1 byte
    int8_t f3; // 1 byte
};

How to use alignas so that sizeof(test) would be exactly 6 bytes?

alignas(1) is not accepted by compiler (gcc, msvc, clang) (error like: error: requested alignment is less than minimum alignment of 4 for type 'test').

UPD. This variant works OK, of course:

#pragma pack(push, 1)

struct alignas(?) test
{
    int32_t f1; // 4 bytes
    int8_t f2; // 1 byte
    int8_t f3; // 1 byte
};

#pragma pack(pop)

But is there a way to do it without preprocessor using only standard C++11/14?

What are the required members? Currently your three members will always add up to 6 bytes — Nick Strupat, Nov 11 '15 at 15:08

score 3 · Accepted Answer · answered Nov 11 '15 at 14:43

3

No. alignas only lets you make alignment stricter, and only up to the maximum alignment of standard types.

The standard provides no mechanism for misaligning types.

answered Nov 11 '15 at 14:43

rici

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Use alignas to align struct

1 Answers1