Debug Assertion Failed in Visual Studio 2019 "string subscript out of range" C++

Question

I'm making a game in C++ which I hope can successfully create a universe of its own procedurally, however, I've encountered an assertion error with the galaxy generation. I have a class for Stars with the following parameters for the constructor:

Stars(std::string newStarName = WordGenerator(), double starPicker = std::rand() % 100, int newStarPosX = std::rand() % 500, int newStarPosY = std::rand() % 500)

I also have a function which can create stars at random:

void GenerateStar(std::string newStarName, double starPicker, int newStarPosX, int newStarPosY) {
Stars newStar(newStarName,  starPicker,  newStarPosX,  newStarPosY);
//allStars.push_back(newStar);
allStarsNames.push_back(newStar.starName);}

And the Galaxy class constructor is as follows:

Galaxy() {
    int starCounter = 0;
    while (starCounter < 5) {
        GenerateStar(WordGenerator(), std::rand() % 100, std::rand() % 500, std::rand() % 500);
        starCounter++;
    }
    

        
    
}

When I try running the program after initializing a galaxy in main visual studio gives me an error screen. error box

I've tried changing the default arguments, changing the parameters of the GenerateStar function, and changed which arguments were passed into the function call in the Galaxy constructor but nothing seems to work.

The definition of the WordGenerator function:

std::string WordGenerator() {
std::vector<char> alphabet = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };
std::string word;
int counter = 2 + std::rand() % 5;
while (counter > 0) {
   word = word + alphabet[std::rand() % alphabet.size()];
   counter--;
}
for (int i = 0; i < word.size(); i++) {
    if (CohrnceAnalyzer(word[i], word[i + 1]) == true) {
        word[i+1] = alphabet[std::rand() % alphabet.size()];
    }
}
return word;}

And for the Coherence Analyzer function:

bool CohrnceAnalyzer(char firstLetter, char secondLetter) {
std::vector<char> alphabet = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
std::vector<char> firstLetters = { 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'c', 'c', 'c', 'c', 'c', 'c', 'c', 'd','d', 'd', 'd', 'd', 'd', 'd', 'd', 'd', 'd', 'f', 'f' };
std::vector<char> secondLetters = { 'd', 'f', 'g', 'm', 'n', 'p', 'q', 'x', 'b', 'g', 'j', 'm', 'n', 'v', 'w', 'b', 'c', 'd', 'f', 'g', 'm', 'n', 'p', 'q', 'x', 'b', 'j'};
for (int i = 0; i < firstLetters.size(); i++) {
    if (firstLetter == firstLetters[i] && secondLetter == secondLetters[i]) {
        
        return true;
    }
    else {
        return false;
    }}}

The thing is that your error says *string subscript out of range* but there is no string subscripting in the code you have shown us, none at all. If I had to guess I would say the error is in the `WordGenerator` function but I'm only guessing. — john, Jun 17 '22 at 19:34
Anyway Visual Studio has a very good debugger, best in the business. Now would be a good time to learn how to use it. — john, Jun 17 '22 at 19:35
The WordGenerator function creates a random string word with a length from 3-7. — JacobFewell, Jun 17 '22 at 19:37
Care to post that code, see if my guess is correct? Of course it might not be. — john, Jun 17 '22 at 19:38
Press Retry and Visual Studio will take you to the line of code that this occurs on. — drescherjm, Jun 17 '22 at 19:42
After putting the section of WordGenerator which uses the coherence analyzer function into a multi-line comment the error still gets thrown. — JacobFewell, Jun 17 '22 at 19:47
So then after you fixed the bug identified in the answer press Retry again to have Visual Studio tell you where the additional out of bounds access is. — drescherjm, Jun 17 '22 at 19:49
Please provide a minimal reproducible example. See [How to create a Minimal, Reproducible Example](https://stackoverflow.com/help/minimal-reproducible-example) — Minxin Yu - MSFT, Jun 20 '22 at 02:02

score 3 · Answer 1 · answered Jun 17 '22 at 19:42

3

OK, here's the string subscripting error

for (int i = 0; i < word.size(); i++) {
    if (CohrnceAnalyzer(word[i], word[i + 1]) == true) {
        word[i+1] = alphabet[std::rand() % alphabet.size()];
    }
}

When i == word.size() - 1 then i + 1 == word.size() and so word[i+1] is a string subscripting error.

The bug would go away if you changed i < word.size(); to i + 1 < word.size(); which I think also makes sense with what you are trying to do in that function. But really only you can decide on that.

answered Jun 17 '22 at 19:42

john

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After putting the section of WordGenerator which uses the coherence analyzer function into a multi-line comment the error still gets thrown. – JacobFewell Jun 17 '22 at 19:49
2

We can't help with code we can't see. – drescherjm Jun 17 '22 at 19:50

Debug Assertion Failed in Visual Studio 2019 "string subscript out of range" C++

1 Answers1