结构体位对齐的问题

[childman]

GCC编译器中定义如下：
struct iec_i {
u_char ft :1;
u_short ns :15;
u_char res :1;
u_short nr :15;
}__attribute__((__packed__));

struct iec_s {
u_char ft :1;
u_short res1 :15;
u_char res2 :1;
u_short nr :15;
}__attribute__((__packed__));

struct iec_u {
u_char ft :2;
u_char start_act :1;
u_char start_con :1;
u_char stop_act :1;
u_char stop_con :1;
u_char test_act :1;
u_char test_con :1;
u_char res1;
u_short res2;
}__attribute__((__packed__));

struct iechdr {
u_char start;
u_char length;
u_char raw[0];
union {
struct iec_i ic;
struct iec_s sc;
struct iec_u uc;
}fc;
}__attribute__((__packed__));

得出:
sizeof(struct iec_i)=4
sizeof(struct iec_u)=4
sizeof(struct iec_s)=4
sizeof(struct iechdr)=6

移植到BCB

#pragma pack(1)

struct iec_i {
u_char ft :1;
u_short ns :15;
u_char res :1;
u_short nr :15;
};

struct iec_s {
u_char ft :1;
u_short res1 :15;
u_char res2 :1;
u_short nr :15;
};

struct iec_u {
u_char ft :2;
u_char start_act :1;
u_char start_con :1;
u_char stop_act :1;
u_char stop_con :1;
u_char test_act :1;
u_char test_con :1;
u_char res1;
u_short res2;
};

struct iechdr {
u_char start;
u_char length;
u_char raw[0];
union {
struct iec_i ic;
struct iec_s sc;
struct iec_u uc;
}fc;
};

得出:
sizeof(struct iec_i)=6
sizeof(struct iec_u)=4
sizeof(struct iec_s)=6
sizeof(struct iechdr)=8

怎样才能做到跟GCC里一样的效果？

[childman]

谢谢各位解答，已经得到解决

[friendbcb]

顶起来，学习一下

[YeBinYe]

可以参考http://dev.firnow.com/course/3_program/c++/cppsl/2008830/138884.html

[Waiting4you]

struct iec_i {
    u_short ft :1;
    u_short ns :15; //把类型改成一样
    u_short res :1;
    u_short nr :15;
};

struct iec_s {
    u_short ft :1;
    u_short res1 :15;
    u_short res2 :1;
    u_short nr :15;
};

struct iec_u {
    u_char ft :2;
    u_char start_act :1;
    u_char start_con :1;
    u_char stop_act :1;
    u_char stop_con :1;
    u_char test_act :1;
    u_char test_con :1;
    u_char res1;
    u_short res2;
};

struct iechdr {
    u_char start;
    u_char length;
    u_char raw[0];
    union {
        struct iec_i ic;
        struct iec_s sc;
        struct iec_u uc;
    }fc;
};

[ccrun.com]

毛毛正解. 楼主可以结帖了. 毛毛+100