Is the use of the malloc function in a subfunction causing warnings?

[nenyan]

I use function malloc in a subfunction. then I got warrnings:
incompatible implicit declaration of built-in function 'malloc'
incompatible implicit declaration of built-in function 'free'

The code works well. Is it matter?

#include <stdio.h>
#include <math.h>

int min_in(double *a, int n)
{
  int i, min_i;
  double t;
  t=a[0];
  min_i=0;
  for(i=1;i<n;i++)
  {
    if (t>a[i])
    {
      t=a[i];
      min_i=i;
    }
  }
  return min_i;
}  


void fourweight (int *a, double *b, int n)
{
	int i, k;
	double *c;
	if ( !(c=(double *)malloc(n*sizeof(double))) )    
printf("memory error\n");
	for(i=0;i<n;i++)
		c[i]=b[i];
	for(i=0;i<4;i++)
	{k=min_in(c,n);
	a[i]=k;
	c[k]=10000.0;
	}
free(c);
}

int main()
{
	int i, a[4]={0,0,0,0};
	double b[10]={0.1, 0.2, 0.3, 0.5, 0.11, 0.21, 0.31, 0.9, 1.1, 0.01};
fourweight(a, b, 10);
for (i=0;i<4;i++)
printf("%d, ", a[i]);

}

 

[Borek]

Have you tried Google search? It often helps.

 

[nenyan]

Have you tried Google search? It often helps.

thank you

 

[Mark44]

In case you haven't already figured it out, you need to #include <stdlib.h> for the declarations of malloc and free.

 

[LudusRex]

I would say that the use of the malloc function in a subfunction is not causing the warnings. The warnings are due to the fact that the compiler is not able to recognize the malloc and free functions, which are defined in the <stdlib.h> header file. To resolve this issue, the <stdlib.h> header file needs to be included in the code. It is important to include all necessary header files in order to avoid any potential errors or warnings. Additionally, the code may work well despite the warnings, but it is always best to address any warnings to ensure the code is functioning correctly and to improve its readability and maintainability.