由char *str与char str[]引发的思索

昨天写一个字符串逆置的程序，开始是这么写的：

#include <iostream>
using namespace std;

char* ReverseWord(char* val);

int main()
{
    char *str="hello";

    cout<<ReverseWord(str);

    return 0;
}

char* ReverseWord(char* val)
{
    char* right=val+strlen(val)-1;
    char* left=val;

    //r* right=val;
    //while(*right != '\0')
    //{
    //    right++;
    //}
    //right--;
    //char* temp='a';

    while(right > left)
    {
       *left=*left^*right;
       *right=*left^*right;
       *left=*left++^*right--;
    }

    return val;
}

运行结果：程序编译通过，但运行崩溃

我通过调试，在*left=*left^*right;这句的时候不能调试进去了，出现了下面的情况：

调试过程如下面这篇般难搞：http://hi.baidu.com/%C2%ED%D0%C2%CC%CE/blog/item/393421acbfe3b2034b36d6bc.html

虽然调试看了汇编代码，但还是搞不清楚问题在哪里。后面干脆发了贴，得到了正确答案，哎，谁知问题就在眼皮底下，遇到BUG不要慌啊！

#include <iostream>
using namespace std;

char* ReverseWord(char* val);

int main()
{
    char str[]="hello";

    cout<<ReverseWord(str)<<endl;

    return 0;
}

char* ReverseWord(char* val)
{
    char* right=val+strlen(val)-1;
    char* left=val;

    //r* right=val;
    //while(*right != '\0')
    //{
    //    right++;
    //}
    //right--;
    //char* temp='a';

    while(right > left)
    {
       *left=*left^*right;
       *right=*left^*right;
       *left=*left++^*right--;
    }

    return val;
}

运行结果：olleh

问题的解决紧紧是：将char *str改为了char str[]，其实当问题解决了，也就知道为什么要将将char *str改为char str[]。

所以下面来说说char *str与char str[]的区别：

其实我以前一篇文章，可以说已经讲到了。http://www.cnblogs.com/chenyuming507950417/archive/2011/12/29/2306043.html

还是搜搜网上专家人士的权威理解吧。

（1）The two declarations are not the same.

char ptr[] = "string"; declares a char array of size 7 and initializes it with the characters
s ,t,r,i,n,g and \0. You are allowed to modify the contents of this array.

char *ptr = "string"; declares ptr as a char pointer and initializes it with address of string literal"string" which is read-only. Modifying a string literal is an undefined behavior. What you saw(seg fault) is one manifestation of the undefined behavior.

（2）char *test = "string test"; is wrong, it should have been const char*. This code compiles just because of backward comptability reasons. The memory pointed by const char* is a read-only memory and whenever you try to write to it, it will invoke undefined behavior. On the other hand char test[] = "string test" creates a writable character array on stack. This like any other regualr local variable to which you can write.

看了上面两条，其它无非都是些讲指针与数组的问题了。

原帖：（1）http://topic.csdn.net/u/20120404/20/5ed24daa-6a18-41b0-be25-7df249061976.html

        （2）http://topic.csdn.net/u/20120404/19/b0d265db-5f5f-460d-88d4-0f3471a08e8b.html

参考文献：

（1）http://stackoverflow.com/questions/3862842/difference-between-char-str-string-and-char-str-string

（2）http://hi.baidu.com/%C2%ED%D0%C2%CC%CE/blog/item/393421acbfe3b2034b36d6bc.html

（3）http://blog.csdn.net/lzpaul/article/details/2884095

（4）http://dmacy.bokee.com/4728674.html

（5）http://www.cnblogs.com/octobershiner/archive/2012/04/03/2431544.html#2347328  （字符串的逆序之旅）
（6）陈皓：http://blog.csdn.net/haoel/article/details/1395358