c – 使用std :: memcpy在内存中移动对象

§3.9.2

For any object (other than a base-class subobject) of trivially copyable type T,whether or not the object holds a valid value of type T,the underlying bytes (1.7) making up the object can be copied into an array of char or unsigned char.40 If the content of the array of char or unsigned char is copied back into the object,the object shall subsequently hold its original value.

#define N sizeof(T)
char buf[N];
T obj; // obj initialized to its original value
std::memcpy(buf,&obj,N); // between these two calls to std::memcpy,// obj might be modified
std::memcpy(&obj,buf,N); // at this point,each subobject of obj of scalar type
                           // holds its original value

§3.9.3

对于任何简单的可复制类型T,如果指向T的两个指针指向不同的T对象obj1和obj2,其中obj1和obj2都不是基类子对象,如果构成obj1的基础字节(1.7)被复制到obj2,41 obj2中随后应保持与obj1相同的值. [例如：

T* t1p;
T* t2p;
    // provided that t2p points to an initialized object ...
std::memcpy(t1p,t2p,sizeof(T));
    // at this point,every subobject of trivially copyable type in *t1p contains
    // the same value as the corresponding subobject in *t2p