c - 6.3.1.1p2 的含义，要点 2

Question

6.3.1.1p2说

The following may be used in an expression wherever an int or unsigned int may be used:

• An object or expression with an integer type (other than int or unsigned int) whose integer conversion rank is less than or equal to the rank of int and unsigned int.

• A bit-field of type _Bool, int, signed int, or unsigned int.

第二个要点背后的意图是什么？

为什么要忽略排名低于 int 的其他类型的整数字段？

这是否意味着我可以做例如:

printf("%d\n", (struct{ _Bool x:1; }){0}.x);

但不是:

printf("%d\n", (struct{ unsigned short x:1; }){0}.x);

Answer 1

大概这是因为 6.7.2.1p5 :

A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed int, unsigned int, or some other implementation-defined type. It is implementation-defined whether atomic types are permitted.

即无论如何，您不能可移植地创建其他类型的位域。