Cant's pass a 2D array to a function in C-CodePudding

I was following internet tutorials on this topic, but I have the following situation:

I have a function with the following signature:

void func(long& rows, long& columns, int array[][columns]);

and I'm trying to use the function like this:

int matrix[5][4] = {0,  -1,  2,  -3,
                    4,  -5,  6,  -7,
                    8,  -9,  10, -11,
                    12, -13, 14, -15,
                    16, -17, 18, -19};

long rows = 5;
long columns = 4;

func(rows, columns, matrix);
^--- 'No matching function for call to 'func''

What is the problem? Why can't it call the function?

CodePudding user response：

Variable length arrays is not a standard C features.

You could declare the function and the array the following way

const size_t columns = 4;

void func( size_t rows, const int array[][columns]);

//...


int matrix[][columns] = { {  0,  -1,   2,  -3 },
                          {  4,  -5,   6,  -7 },
                          {  8,  -9,  10, -11 },
                          { 12, -13,  14, -15 },
                          { 16, -17,  18, -19 } };

func( sizeof( matrix ) / sizeof( *matrix ),  matrix);

//...

void func( size_t rows, const int array[][columns] )
{
    std::cout << rows << columns << array[0][1];
}

Pay attention to that as the number of columns is well-known there is no sense to pass it to the function. And moreover there is no sense to pass the number of rows and columns by reference.

CodePudding user response：

Have you actually defined func in your program? The following source code compiles and works fine for me

#include <iostream>

#define ROW 5
#define COLUMN 4

void func(long &rows, long &columns, int array[][COLUMN]);

int main()
{
    int matrix[ROW][COLUMN] = {0, -1, 2, -3,
                          4, -5, 6, -7,
                          8, -9, 10, -11,
                          12, -13, 14, -15,
                          16, -17, 18, -19};

    long rows = 5;
    long columns = 4;

    func(rows, columns, matrix);
    return 0;
}

void func(long &rows, long &columns, int array[][COLUMN])
{
    std::cout << rows << columns << array[0][1];
}