How to fix "the monitored command" error?

Question

I'm trying to create a program that stores words of a string within the space in an array(For example: If user inputs - "Hello what's up" ,So i want to store Hello, What's,Up in an array of thier respective indices (Hello in 0th index,What's in 1st index and up in 2nd index). I'm using c method of DMA in c++ to achieve this. Following is my code- https://code.sololearn.com/cNWxZV9IoG4q/?ref=app

#include <iostream>
#include <sstream>
#include <cstdlib>
using namespace std;

int main() {
    string sentence;
    getline(cin,sentence);
    stringstream ss(sentence);
    string *words;
    int count=0;
    
    while(ss>>sentence)
    {
     if(count==0)
     {        
   words=
  (string*)malloc((count+1)*sizeof(string));
  *(words+count)=ss.str();
  count++;
  continue;
     }
      words=(string*)realloc(words, (count+1)*sizeof(string));
    *(words+count)=ss.str();
    free(words);
      count++;
    }
    
    return 0;
}

But , I'm getting error , Could anyone please fix it?

Answer 1

Don't use C in C++. Just use a std::vector to store the words:

std::string word;
std::vector<std::string> words;

while (ss >> word) {
    words.push_back(word);
}

And then you can print the individual words like so:

for (auto& word: words) {
    std::cout << word << '\n';
}

Or if you wish to use indices:

for (std::size_t i = 0; i  < words.size(); ++i) {
    std::cout << i << ": " << words[i] << '\n';
}

The reason why your code fails is, as @heapunderrun mentioned, the fact that std::string has a constructor. If you don't call the constructor in some way, then the string will be in an indeterminate state. When you try to assign to such a string, like in:

*(words+count)=ss.str();

Then your program will crash. If you really want to use manual memory allocation, then you have to use new and delete. You can use malloc() if you really want to, but then you still should use placement new to ensure the std::string objects are correctly constructed inside the memory you allocated. Finally, you probably can't use realloc() safely, you would have to malloc() a new array, copy everything properly to the new array, then free() the old array.