我试图编译以下联合时会弹出此警告: 10:5: note: offset of packed bit-field 'main()::pack_it_in::<anonymous struct>::two' has changed in GCC 4.4
#pragma GCC diagnostic ignore "-Wpacked-bitfield-compat"
union pack_it_in {
struct
{
uint8_t zero : 3;
uint8_t one : 2;
uint8_t two : 6;
uint8_t three : 4;
uint8_t four : 1;
} __attribute__((packed)) u8_2;
uint16_t u16;
};
#pragma GCC diagnostic pop
#pragma不忽略该注释。有没有办法使#pragma不需要使用-Wno-packed-bitfield-compat
,因为我希望此警告仅在我的八个工会中忽略了?
只是遇到了类似的问题。似乎GCC只是不喜欢穿越类型宽度的Bitfields(如示例中two
所做的那样)吗?
如果将所有类型更改为uint16_t
,GCC接受:
union pack_it_in {
struct
{
uint16_t zero : 3;
uint16_t one : 2;
uint16_t two : 6;
uint16_t three : 4;
uint16_t four : 1;
} __attribute__((packed)) u8_2;
uint16_t u16;
};
布局是您想要的,即使这些成员的类型可能不是。
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wpacked-bitfield-compat"
union pack_it_in {
struct
{
uint8_t zero : 3;
uint8_t one : 2;
uint8_t two : 6;
uint8_t three : 4;
uint8_t four : 1;
} __attribute__((packed)) u8_2;
uint16_t u16;
};
#pragma GCC diagnostic pop