struct x
{
char a : 1; // statement 1
char c : 3; // statement 2
};
如果这个结构将是什么大小.声明1和2的含义是什么？
解决方法
它意味着占用1位的存储器而c占用3位的存储器.
结构的大小将是：
至少4位
填充(比特)
最有可能的是,它将是8位,即：1个字节
因为,
如果一系列位字段没有达到int的大小,则可以进行填充.填充量由结构构件的对准特征确定.
什么是比特字段？
From IBM documentation:
Both C and C++ allow integer members to be stored into memory spaces smaller than the compiler would ordinarily allow. These space-saving structure members are called bit fields,and their width in bits can be explicitly declared. Bit fields are used in programs that must force a data structure to correspond to a fixed hardware representation and are unlikely to be portable.
The Syntax for declaring a bit field is as follows:
>>-type_specifier–+————+–:–constant_expression–;—><
‘-declarator-‘A bit field declaration contains a type specifier followed by an optional declarator,a colon,a constant integer expression that indicates the field width in bits,and a semicolon. A bit field declaration may not use either of the type qualifiers,const or volatile.
