Extra garbage values outside dimensions char array - c++

Question

I have a 2 dimensional char array char** field. I have a method get_field() which makes a copy of this char array and returns this copy.
char** Game::get_field() {
char** copy = new char*[this->width_field];
for (unsigned int i = 0; i < this->width_field; i++)
copy[i] = new char[this->length_field];
for (unsigned int i = 0; i < this->width_field; i++) {
for (unsigned int j = 0; j < this->length_field; j++)
copy[i][j] = this->field[i][j];
}
return copy;
}
When I output the values of the copy to the console I get some garbage values after each row. However each row of the char array does contain the '\0' character to mark the end of the string. After some investigation with the debugger I found out that in the get_field() method extra garbage values are added outside the dimensions specified when declaring the array.
When length_field equals 52 I got 51 dashes plus the '\0' character like in the image and after that some extra garbage values. Where do these garbage values come from and how do I get rid of them?
[EDIT:]
This is the code that does the output to the console:
char** field = game->get_field();
for (unsigned int i = 0; i < 13; i++) {
cout << field[i] << endl;
}
This is the code how the initial field is setup:
this->field = new char*[this->width_field];
for (unsigned int i = 0; i < this->width_field; i++)
this->field[i] = new char[this->length_field];
this->setup_field();
void Game::setup_field(){
this->field[0] = "---------------------------------------------------\n\0";
this->field[1] = "| | |\n\0";
this->field[2] = "| | |\n\0";
this->field[3] = "| | |\n\0";
this->field[4] = "|---- | ----|\n\0";
this->field[5] = "| | -|- | |\n\0";
this->field[6] = "| | | | | | |\n\0";
this->field[7] = "| | -|- | |\n\0";
this->field[8] = "|---- | ----|\n\0";
this->field[9] = "| | |\n\0";
this->field[10] = "| | |\n\0";
this->field[11] = "| | |\n\0";
this->field[12] = "---------------------------------------------------\n\0";
}

Answer 1

Neither the C++ standard nor the Microsoft implementation gives any guarantees about memory which does not belong to you.
Accessing it for any reason is undefined behavior => anything may happen.
If you hand a char* which does not point to a 0-terminated string to a function expecting one, it will access out-of-bounds memory until it finds a 0 or it crashs in some manner.
That should sufficiently explain your "added garbage".
Sidenote: Is there any reason you cannot allocate all needed memory in one chunk?
As you later added after prompting, your copied lines are not 0-terminated.
Full size of any line: length + 1: 51 printable + 1 newline + 1 terminator
Tip: If you cannot use strdup and / or memdup, define them for yourself.

Answer 2

When length_field equals 52 I got 51 dashes plus the '\0' character
You actually have 54 characters in your Game::setup_field() strings:
51 dashes
One \n
One \0
One implicit \0 to end the string
Thus in your Game::get_field() method when you copy only 52 characters (stopping at the \n) you don't copy the \0 character resulting in an unterminated string.
Better to use a vector<string> or be more careful/explicit of array lengths when you initialize or copy things.

Answer 3

You really don't want to do it that way. Try this:
#include <vector>
#include <string>
std::vector<std::string> Game::get_field() {
std::vector<std::string> copy(this->width_field);
for (unsigned int i = 0; i < this->width_field; i++) {
for (unsigned int j = 0; j < this->length_field; j++) {
copy[i].push_back(this->field[i][j]);
}
}
return copy;
}