C++ Program Crash on file output

Question

I am trying to write a program that takes a list of names and then outputs it to a .txt file.

This is my code:

void setNames() // Set method that takes a series of names.
{
  nameTags = new char*[numberOfNames];
  for (int i=0; i<=numberOfNames; i++)
  {
    nameTags[i] = new char[128];
    cout << "Input information for name " << i << ": " << "\n";
    cin.getline(namesSet, sizeof(namesSet));
    strcpy(nameTags[i], namesSet);
  }
}

ostream& operator<< (ostream& ostr, const Names& names) // <<operator
{
  ostr << "#############################" << endl;
  ostr << names.getAuthor();
  ostr << names.getNumberOfNames();
  for(int i=0; i<=names.numberOfNames; i++)
  {
    ostr << names.nameTags [i] << "\n";
  }
  return ostr;
}

Now my program works fine and prints to a terminal. However, when I try running this after the ofstream it crashes and is not very good. For example, if I want to input 10 names, and save it to disk it crashes.

ofstream outputfile (names.getFileName());
if(outputfile.is_open())
{
  outputfile << names; // I believe I go wrong here.
  outputfile.close();
}

I am new to C++ and I would greatly appreciate it if someone could help me out with my problem. I have been spending hours trying to fix it.

Use std::string and std::vector<std::string> instead of a dynamically allocated array of char* — Borgleader
– Borgleader, Commented Nov 3, 2014 at 19:55
If getline fails then your buffers will all be full of garbage which could cause the problem — M.M
– M.M, Commented Nov 3, 2014 at 20:57
@MattMcNabb I think it may be the getline that causes the bug. I have declared namesSet as char namesSet[100] — user4167396
– user4167396, Commented Nov 3, 2014 at 22:19

Fred Larson · Accepted Answer · 2014-11-03 20:04:21Z

1

The problem is with statement:

for (int i=0; i<=numberOfNames; i++)

Instead it should be

for (int i=0; i < numberOfNames; i++)

Also in the stream insertion operator it should be:

for(int i=0; i < names.numberOfNames; i++)

edited Nov 3, 2014 at 20:04

Fred Larson

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answered Nov 3, 2014 at 19:55

Sumeet

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5 Comments

Fred Larson Over a year ago

+1. Writing past the end of the buffer could definitely account for it.

user4167396 Over a year ago

I just tried that... doesn't make a difference. Like I mentioned, I think its the output file stream

Fred Larson Over a year ago

@user4167396: This is a bug nonetheless, leading to undefined behavior. You may have other bugs as well.

Fred Larson Over a year ago

@user4167396: If fixing this bug didn't solve the problem, I think you have errors in code you haven't shown. For example, I'm suspicious of sizeof(namesSet), since sizeof on a pointer is a common bug. But you haven't shown the declaration of namesSet.

user4167396 Over a year ago

@FredLarson namesSet is declared as char namesSet[100]

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