Undefined reference?

MHS1986 (26)

Hi, i am new to C++ and while practicing i am getting an undefined reference error from the compiler and i dont know why... Can anyone see what the problem is below?

#include <iostream>
#include <iomanip>

using namespace std;

const int NUMBER_OF_ROWS = 6;
const int NUMBER_OF_COLUMNS = 5;

void printMatrix(int matrix[][NUMBER_OF_COLUMNS], int NUMBER_OF_ROWS);

void sumRows(int matrix[][NUMBER_OF_COLUMNS], int NUMBER_OF_ROWS);

void largestInRows (int matrix[][NUMBER_OF_COLUMNS], int NUMBER_OF_ROWS);

int main()
{
int board [NUMBER_OF_ROWS][NUMBER_OF_COLUMNS]
= {{17, 8, 24, 10, 28},
{9, 20, 16, 55, 90},
{25, 45, 35, 8, 78},
{5, 0, 96, 45, 38},
{76, 30, 8, 14, 28},
{9, 60, 55, 62, 10}};
printMatrix(board, NUMBER_OF_ROWS);
cout << endl;
sumRows(board, NUMBER_OF_ROWS);
cout << endl;
largestInRows(board, NUMBER_OF_ROWS);

return 0;
}

void printMatrix(int matrix[][NUMBER_OF_COLUMNS])
{
int row;
int col;

for (row = 0; row < NUMBER_OF_ROWS; row++)
{
for (col = 0; col < NUMBER_OF_COLUMNS; col++)
cout << setw(5) << matrix[row][col] << " ";
cout << endl;
}
}

void sumRows(int matrix[][NUMBER_OF_COLUMNS], int NUMBER_OF_ROWS)
{
int row;
int col;
int sum = 0;

for (row = 0; row < NUMBER_OF_ROWS; row++)
{
for (col = 0; col < NUMBER_OF_COLUMNS; col++)
sum = sum + matrix[row][col];

cout << "Sum of row " << row + 1 << " = " << sum << endl;
}
}

void largestInRows (int matrix[][NUMBER_OF_COLUMNS], int NUMBER_OF_ROWS)
{
int row;
int col;
int largest;

for (row = 0; row < NUMBER_OF_ROWS; row++)
{
largest = matrix[row][0];

for (col = 1; col < NUMBER_OF_COLUMNS; col++)
if (matrix[row][col] > largest)
largest = matrix[row][col];

cout << "The largest element in row " << row + 1 << " = "
<< largest << endl;
}
}

salem c (3700)

https://cplusplus.com/articles/jEywvCM9/

You didn't post the error messages.

This
> void printMatrix(int matrix[][NUMBER_OF_COLUMNS], int NUMBER_OF_ROWS);

is not this
> void printMatrix(int matrix[][NUMBER_OF_COLUMNS])

MHS1986 (26)

Hi, apologies for that, please see below

=== Build: Debug in Example 8-11 (compiler: GNU GCC Compiler) ===
In function `main':|
undefined reference to `printMatrix(int (*) [5], int)'
error: ld returned 1 exit status
=== Build failed: 2 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===

The code is exactly as in the text book, can you explain why it is wrong?

Geckoo (362)

Hello. Your function definition is different according to its declaration :)
You forgot something in your definition :

// your declaration
void printMatrix(int matrix[][NUMBER_OF_COLUMNS], int NUMBER_OF_ROWS);
// your definition ???
void printMatrix(int matrix[][NUMBER_OF_COLUMNS]) {...}

When you have a green wavy line on Visual Studio, often it means that you have no valid definition for a given declaration. Change you definition for this one and it works :

void printMatrix(int matrix[][NUMBER_OF_COLUMNS], int NUMBER_OF_ROWS)
{
    int row;
    int col;
// ... 
}


   17     8    24    10    28
    9    20    16    55    90
   25    45    35     8    78
    5     0    96    45    38
   76    30     8    14    28
    9    60    55    62    10

Sum of row 1 = 87
Sum of row 2 = 277
Sum of row 3 = 468
Sum of row 4 = 652
Sum of row 5 = 808
Sum of row 6 = 1004

The largest element in row 1 = 28
The largest element in row 2 = 90
The largest element in row 3 = 78
The largest element in row 4 = 96
The largest element in row 5 = 76
The largest element in row 6 = 62

PS : Respectfully, it is better if you format your code according to the tag <code> as I did. Thanks ++

Last edited on

keskiverto (10402)

Part of the problem is that you have global: const int NUMBER_OF_ROWS = 6;

That value does not have to be global. It can be in main():

int main()
{
    const int NUMBER_OF_ROWS = 6;
    int board [NUMBER_OF_ROWS][NUMBER_OF_COLUMNS];
    // ...
}

If you had had that, then compiler would have stopped at:

void printMatrix(int matrix[][NUMBER_OF_COLUMNS])
{
  int row;
  int col;

  for (row = 0; row < NUMBER_OF_ROWS; row++) // ERROR: What is NUMBER_OF_ROWS?
  {
    for (col = 0; col < NUMBER_OF_COLUMNS; col++)
      cout << setw(5) << matrix[row][col] << " ";
    cout << endl;
  }
}

There is also "masking":

const int NUMBER_OF_ROWS = 6; // global
void printMatrix(int matrix[][NUMBER_OF_COLUMNS], int NUMBER_OF_ROWS)
{
  // NUMBER_OF_ROWS here is local variable, not the global.
  // Someone could call this function with printMatrix( answer, 42 );
  // ...
}

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