混淆“std :: out_of_range”错误 [英] Confusing "std::out_of_range" Error

问题描述

我一直在调试这个错误的最后2个小时，知道自己，我不能睡觉，如果我不上床睡觉前请求帮助。我为我的游戏写了一个模型加载器，现在我使用一个漂亮的脆弱的方法来拆分字符串。然而，它工作在几乎相同的行，然后随机不。我使用string.substr（），我相信错误意味着它试图在字符串中不存在的位置开始。调用堆栈说明它发生在这一行：

I've been debugging this error for the last 2 hours, and knowing myself I won't be able to sleep if I don't ask for help before I go to bed. I'm writing a model loader for my game, and just for now I'm using a pretty flimsy method to split strings. However, it works on nearly identical lines, then randomly doesn't. I'm using string.substr(), and I believe the error means its trying to start at a location that doesn't exist in the string. The call stack says its happening on this line:

v1 = v1.substr(s.find(",")+1);

，并使用打印邮件的断点，表示

and by using a breakpoint that prints a message, it says

顶点1使用1,1，整个字符串是173,1,1 175,1,1
174,1,1 p>

Vertex 1 is using "1,1" and the entire string is "173,1,1 175,1,1 174,1,1"

其中Vertex 1是v1的值，string是s的值。

where Vertex 1 is the value of v1, and string is the value of s.

这是整个函数：

FaceData data;
s = s.substr(5); //remove "FACE "
string v1, v2, v3;

//vertex 1
v1 = s.substr(0, s.find(" "));

data.vertexIndexes[0] = atoi(v1.substr(0, s.find(",")).c_str());
v1 = v1.substr(s.find(",")+1);
data.textureIndexes[0] = atoi(v1.substr(0, s.find(",")).c_str());
v1 = v1.substr(s.find(",")+1);
data.normalIndexes[0] = atoi(v1.c_str());

//vertex 2
s = s.substr(s.find(" ")+1);
v2 = s.substr(0, s.find(" "));

data.vertexIndexes[1] = atoi(v2.substr(0, s.find(",")).c_str());
v2 = v2.substr(s.find(",")+1);
data.textureIndexes[1] = atoi(v2.substr(0, s.find(",")).c_str());
v2 = v2.substr(s.find(",")+1);
data.normalIndexes[1] = atoi(v2.c_str());

//vertex 3
s = s.substr(s.find(" ")+1);
v3 = s;

data.vertexIndexes[2] = atoi(v3.substr(0, s.find(",")).c_str());
v3 = v3.substr(s.find(",")+1);
data.textureIndexes[2] = atoi(v3.substr(0, s.find(",")).c_str());
v3 = v3.substr(s.find(",")+1);
data.normalIndexes[2] = atoi(v3.c_str());

return data;

传递给函数的std :: string's'总是如下所示：
FACE X，X，XX，X，XX，X，X
其中x是一个数字。

the std::string 's' being passed to the function always looks like this: "FACE X,X,X X,X,X X,X,X" where x is a number.

分割字符串...

现在，我不明白为什么它在这里得到这个错误...它似乎几乎只是随机发生。我不明白为什么它不能使用

Now, I don't understand why it is getting this error here... It seems like it's almost just happening randomly. I can't understand why it won't work with

173,1,1 175,1,1 174,1,1

173,1,1 175,1,1 174,1,1

但它适用于

175 ，2,2 176,2,2 175,2,2

175,2,2 176,2,2 175,2,2

推荐答案

不确定我是否正确解释您的问题，但根据您提供的信息，这似乎是您正在做的：

I'm not sure I'm interpreting your question correctly, but given the information you provided, this seems to be what you're doing:

#include <string>
#include <iostream>

int main() {
    std::string v1 = "1,1";
    std::string s = "173,1,1 175,1,1 174,1,1";

    try {
        v1 = v1.substr(s.find(",")+1);
    }
    catch (const std::out_of_range& e) {
        std::cout << "out_of_range: " << e.what() << std::endl;
        return 1;
    }
    return 0;
}

在这种情况下， s.find ）将返回 3 （， 位于位置3），然而由于 v1 只有三个字符，所以唯一有效的索引在 [0,2] 。传入 3 或与 +1 4 超出 v1 的范围。

In that case, s.find(",") will return 3 (the first , in s is at position 3), however since v1 only has three characters the only valid indexes are between [0,2]. Passing in 3, or with the +1 4 would be out of range for v1.

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