复制简单结构时memcpy和'='之间的区别 [英] Difference between memcpy and '=' when copying simple struct

问题描述

考虑复制一个简单的结构，不需要特殊的复制语义.

Consider copy a simple struct which doesn't require special copy semantics.

struct A
{
    char i
    int i;
    long l;
    double b;
    //...maybe more member
}
struct A a;
a.c = 'a'; //skip other member just for illustrate
struct A b;
memset(&a, 0, sizeof(a));
b.c = a.c;
//...for other members, the first way to assign
memcpy(&b, &a, sizeof(b)); //the second way
b = a;    //the third way

这3种方法做同样的事情，看来它们都是正确的.我曾经使用'memcpy'复制简单的结构，但现在看来'='可以做同样的事情.那么使用memcpy和'='有什么区别吗?

The 3 methods do the same thing, and it seems all of them are correct. I used to use 'memcpy' for copying simple structs, but seems now '=' can do the same thing. So is there any difference between using memcpy and '='?

推荐答案

memcpy将结构视为字节的连续数组，并仅复制所有字节.结果，它将始终在成员之后复制填充字节.

memcpy treats the structure as a contiguous array of bytes, and just copies all of them. As a result, it will always copy the padding bytes after members.

=仅需要复制成员.它可能会或可能不会复制填充.

= is only required to copy the members. It might or might not copy the padding.

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