修改 C 字符串常量? [英] Modifying C string constants?

问题描述

可能的重复:
为什么出现分段错误写入字符串?

我想编写一个函数来反转传递给它的给定字符串.但是我不能.如果我为 doReverse 函数(见下面的代码)提供一个字符数组，我的代码运行良好.

I want to write a function that reverses the given string passed into it. But, I can not. If I supply the doReverse function (see code below) with a character array, my code works well.

我不明白为什么这不起作用.我可以在 doReverse 中访问 str[0]，但我无法使用字符指针更改数组的任何值.有什么想法吗?

I can't figure out why this does not work. I am able to access str[0] in doReverse, but I can't change any value of the array by using a char pointer. Any ideas?

void doReverse(char *str) {
    str[0] = 'b';
}

void main(void) {
    char *str = "abc";
    doReverse(str);
    puts(str);
}

更新:

我知道如何通过向其传递字符数组来编写反向函数:

Update:

I know how to do write a reverse function by passing a character array to it:

void reverse1(char p[]) {
    int i, temp, y;

    for (i = 0, y = strlen(p); i < y; ++i, --y) {
        temp = p[y-1];
        p[y-1] = p[i];
        p[i] = temp;
    }
}

但是，我想编写另一个版本，将字符指针作为参数.

But, I want to write another version that gets a char pointer as a parameter.

推荐答案

最简单的解决方案是将str的声明改为

The simplest solution is to change the declaration of str to

char str[] = "abc";

这使 str 成为初始化为字符串abc"的字符数组.目前，您将 str 作为指向字符的指针，初始化为指向由字符串文字描述的字符串.有一个关键区别:字符串文字是只读的，以便编译器在存储它们的位置上具有最大的灵活性；修改它们是UB.但是 char 数组是可变的，因此可以修改它们.

This makes str an array of char that is initialized to the string "abc". Currently you have str as a pointer-to-char initialized to point to a string described by a string literal. There is a key difference: string literals are read-only to give the compiler maximum flexibility on where to store them; it is UB to modify them. But arrays of char are mutable, and so it's okay to modify those.

附注.main() 返回一个 int.

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