Warnings with pointers or declaration in multidimentional arrays while passing to a function

Question

#include <stdio.h>

#define MAXB 32
#define MAXL 18
#define MAXD 50

void floyd(char a[][18],int n, int m);/*Function definition*/

int main()
{
int i = 0,temp,n,m,j=0,k=0,col;
int numlines = 0,numcolumn=0;
char buf[MAXB] = {0},c,check;
char a[MAXL][MAXD];

FILE *fp = fopen("num.txt", "r");

if (fp == 0)
{
   fprintf(stderr, "failed to open inputs/control.txt\n");
   return 1;
}

while (fscanf(fp, "%hhd", &a[i][k]) > 0) {

  //check to see if the next character is a comma
fscanf(fp, "%c", &check);

//if it is a comma, go to the next char, else go to the next line
if (check == ',') 
{k++;
 col++;} 
else 
{i++; 
 k=0;}

}
numlines = i;
m=((col/numlines)+1);
printf("\n\t\t\t\t\tInput Matrix\n\n");
for (i = 0; i < numlines; i++){
printf("\t\t\t\t");
    for (j = 0; j <(col/numlines)+1; j++){
    if(a[i][j]==-12)
printf("inf\t");/*Printing inf as infinity in the input matrix*/
else

        printf (" %hhd\t",a[i][j]);}
printf("\n");
}

floyd(a,n,m);

return (0);
}

void floyd(char a[][18],int n, int m)/*Function definition*/
{
int k,i,j;
for(k=0;k<n;k++)/*n is the no.of vertices of the graph and k represents  table no.*/
{
for(i=0;i<n;i++)/*i represents row no. within a table*/
{
for(j=0;j<m;j++)/*j represents column no. within a row*/
{
if(a[i][j]>(a[i][k]+a[k][j]))/*Minimum is to be selected*/
/*a[i][j] denotes distance between ith vertex and jth vertex*/
a[i][j]=(a[i][k]+a[k][j]);
}
}
}
printf("\n The final matrix where we can find the shortest distance:\n"); 
for(i=0;i<n;i++)
{
printf("\ninside\n\n");
for(j=0;j<m;j++){
printf("%hhd",a[i][j]);
}
} 
}

This is my code. I'm new to pointers. I'm getting this error. How do I rectify it ?

In function ‘main’: warning: passing argument 1 of ‘floyd’ from incompatible pointer type [enabled by default] floyd(a,n,m); ^ note: expected ‘char ()[18]’ but argument is of type ‘char ()[50]’ void floyd(char a[][18],int n, int m);/Function definition/ ^

My current output is
              Input Matrix

           0   6   4   2   2   3  
           2   4   5   3   4   5  
           2   4   6   7   6   1  
           1   2   3   4   6   7  
           1   2   3   4  inf  4  
The final matrix where we can find the shortest distance:

I think the output is not being generated due to the warning.

How about void floyd(char (*a)[MAXD],int n, int m) instead? — David C. Rankin
One is using 18 for the second dimension, the other 50. Well, 18 is not equal to 50, right? So pick one, and use it in both places. The error message seemed quite clear about the problem. — Tom Karzes

JimmyNJ JimmyNJ · Accepted Answer · 2016-03-04T20:50:38

You define the variable a as

char a[MAXL][MAXD]

where MAXL is 18 and MAXD is 50 but the function floyd(..) is expecting a to be a type like

char [][18]

I'm not sure if you'll run off the edge of your array or not but you should either change the declaration of floyd(..) to expect a

char[MAXL][MAXD]

argument in the first position or change the variable a in main to be

char[][MAXL]

Hope this helps.

Warnings with pointers or declaration in multidimentional arrays while passing to a function

2 Answers