std :: string构造函数抛出std :: out_of_range异常

Question

Using VS 2012.

I was making hangman. Anyway, I had a function to get a std::string that was the same length as the current word being guessed, but filled with underscores. (as in, blanks).

The function:

std::string getBlankWord(std::vector<std::string> words, int currentWordIndex)
{
    return std::string(words[currentWordIndex], '_');
}

The line it is called on:

currentGuessingString = getBlankWord(words, index);

words is an std::vector, index is an int. words.size() = 22, and index = 0, so I don't know how calling, in this case, words[0] could be the culprit. Anyway, something on this line throws std::out_of_range exception, but I cannot find it.

Thanks.

Answer 1

我觉得你真正想要的更像是：

return std::string(words[currentWordIndex].size(), '_');

Answer 2

Your problem appears because the constructor that ends up being called is the substring constructor (see here )

The first argument is easy to figure out, the second one however will be a char with the ascii value of '_' implicitly casted to a size_t and its' value is most likely bigger than the size of the string you are giving to the constructor which in turn causes your problem