查找故障或错误 [英] Find the fault or error

问题描述

你能找到什么是错用下面的code？

Can you find what is wrong with the following code?

int main(){
    char *p="hai friends",*p1;
    p1=p;
    while(*p!='\0') ++*p++;
    printf("%s %s",p,p1);
}

我预计它会打印空间后跟一个字符串！

I expected it will print space followed by a string!

推荐答案

下面是使用方法 ++ * P ++ ：

#include <stdio.h>
#include <string.h>

int main(int argc, char* argv[]) {
  char *p = "My test string", p1[15];

  strncpy(p1, p, 14);
  p1[14] = 0;
  p = p1;

  while (*p != 0) {
    printf("%c", ++*p++);
  }
}

需要注意的是 P1 是内存中的数组（通常）在栈中分配，而 P （通常

）的指针，只读存储器，它上面的code移动到指向 P1 ，而不是（通常）其中字符串驻留只读位置。某些操作系统和/或编译器会出现其他的行为，但这是建立了现代操作系统为prevent某些类别的病毒保护机制之一。

Note that p1 is an array of memory (usually) allocated on the stack, whereas p is (usually) a pointer to read only memory, which the above code moves to point to p1 instead of the (usually) read only location where the string resides. Some operating systems and/or compilers will exhibit other behavior, but this is one of the protection mechanisms built into modern OSs to prevent certain classes of viruses.

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