2021年12月

第一步：设置.htaccess于根目录

<IfModule mod_rewrite.c>
  Options +FollowSymlinks -Multiviews
  RewriteEngine On

  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteCond %{REQUEST_FILENAME} !-f
  #  RewriteRule ^(.*)$ index.php/$1 [QSA,PT,L]
  RewriteRule ^(.*)$ index.php [L,E=PATH_INFO:$1]
</IfModule>

第二步：

设置-->永久链接-->是否使用地址重写功能-->启用.
注意要“强制启用”

代码

#include <stdio.h>

int main(void)
{
    int urn[5] = {100,200,300,400,500};
    int *ptr1, *ptr2, *ptr3;
    
    ptr1 = urn; //第1个元素地址0x00007ffeefbff470
    ptr2 = &urn[2];  //第3个元素地址0x00007ffeefbff478
    
    printf("ptr1 = %p, *ptr1 = %d, &ptr1 = %p\n", ptr1, *ptr1, &ptr1); //ptr1表示第1个元素地址470  第1个元素值100  表示变量ptr1本身的地址460
    
    ptr3 = ptr1 + 4; //批针与整数和相加意思是，整数与指针指向的类型的字节数相乘 再与初始地址相加（16进制）
    printf("ptr1+4 = %p, *(ptr1+4) = %d\n", ptr1 + 4, *(ptr1 + 4)); //500的地址480  值500  (4*4=16位）
    
    ptr1++; //自增指针，意思是指针移至下一个元素
    printf("ptr1 = %p, *ptrl = %d, &ptr1 =  %p\n", ptr1, *ptr1, &ptr1); //200的地址474  200  prt1指针变量自身的地址460
    
    ptr2--;  //先获取地址再减
    printf("ptr2 = %p, *ptr2 = %d, &ptr2 = %p\n", ptr2, *ptr2, &ptr2); //474   200     ptr2变量自身的变量地址458
    
    --ptr1;
    ++ptr2;
    printf("ptr1 = %p, ptr2 = %p\n", ptr1, ptr2); //470    478
    printf("ptr2 = %p, ptr1 = %p, ptr2 - ptr1 = %td\n", ptr2, ptr1, ptr2 - ptr1); //478  470  2（表示2个整形类型的字节）
    printf("ptr3 = %p, ptr3 - 2 = %p\n", ptr3, ptr3 - 2); //480  478
    
    return 0;
}

结果

ptr1 = 0x7ffeefbff470, *ptr1 = 100, &ptr1 = 0x7ffeefbff460
ptr1+4 = 0x7ffeefbff480, *(ptr1+4) = 500
ptr1 = 0x7ffeefbff474, *ptrl = 200, &ptr1 =  0x7ffeefbff460
ptr2 = 0x7ffeefbff474, *ptr2 = 200, &ptr2 = 0x7ffeefbff458
ptr1 = 0x7ffeefbff470, ptr2 = 0x7ffeefbff478
ptr2 = 0x7ffeefbff478, ptr1 = 0x7ffeefbff470, ptr2 - ptr1 = 2
ptr3 = 0x7ffeefbff480, ptr3 - 2 = 0x7ffeefbff478
Program ended with exit code: 0

Xcode10.2与macOS运行。

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