memcpy 和 memmove

在发生overlap的情况下，memcpy在不同的平台是有差别的

这是例子

#include "stdio.h"

char str1[9] = "aabbccdd";

int main( void )
{
    printf("The string: %s\n", str1);
    memcpy(str1 + 2, str1, 6);
    printf("New string: %s\n", str1);

    strcpy(str1, "aabbccdd");   // reset string

    printf("The string: %s\n", str1);
    memmove(str1 + 2, str1, 6);
    printf("New string: %s\n", str1);
}

 在不同的Target上，memcpy的行为不同，memmove是一致的

所以memcpy的时候要注意这个问题

gcc on Ubuntu:
The string: aabbccdd
New string: aaaaaabb
The string: aabbccdd
New string: aaaabbcc

Some ARM Target
The string: aabbccdd
New string: aaaabbbb
The string: aabbccdd
New string: aaaabbcc