I get this error when I try to compile my code for CS50 week 4 filter-less - clang

Question

I am doing Week 4 Filter-less for CS50, I get an error whne I try to compile my code
When I complie it is see this erorr.
/usr/bin/ld: /lib/x86_64-linux-gnu/Scrt1.o: in function _start': (.text+0x1b): undefined reference to main'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [: helpers] Error 1
This is my code
#include "helpers.h"
#include <math.h>
// Convert image to grayscale
void grayscale(int height, int width, RGBTRIPLE image[height][width])
{
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
float r = image[i][j].rgbtRed;
float g = image[i][j].rgbtGreen;
float b = image[i][j].rgbtBlue;
float grey = round((b + g + r)/3.0);
image[i][j].rgbtRed = image[i][j].rgbtGreen = image[i][j].rgbtBlue = grey;
}
}
return;
}
// Convert image to sepia
void sepia(int height, int width, RGBTRIPLE image[height][width])
{
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width / 2; j++)
{
int w = width - (j + 1);
RGBTRIPLE tmp = image[i][j];
image[i][j] = image[i][w];
image[i][w] = tmp;
}
}
return;
}
// Reflect image horizontally
void reflect(int height, int width, RGBTRIPLE image[height][width])
{
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
int b = image[i][j].rgbtBlue;
int g = image[i][j].rgbtGreen;
int r = image[i][j].rgbtRed;
int sepiaRed = round((0.393 * r) + (0.769 * g) + (0.189 * b));
int sepiaGreen = round((0.349 * r) + (0.686 * g) + (0.168 * b));
int sepiaBlue = round((0.272 * r) + (0.534 * g) + (0.131 * b));
if (sepiaRed > 255)
{
sepiaRed = 255;
}
if (sepiaGreen > 255)
{
sepiaGreen = 255;
}
if (sepiaBlue > 255)
{
sepiaBlue = 255;
}
image[i][j].rgbtBlue = sepiaBlue;
image[i][j].rgbtGreen = sepiaGreen;
image[i][j].rgbtRed = sepiaRed;
}
}
return;
}
// Blur image
void blur(int height, int width, RGBTRIPLE image[height][width])
{
RGBTRIPLE tmp[height][width];
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
tmp[i][j] = image[i][j];
}
}
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
int totalRed = 0;
int totalGreen = 0;
int totalBlue = 0;
float counter = 0.00;
for (int x = -1; x < 2; x++)
{
for (int y = -1; y < 2; y++)
{
int X = i + x;
int Y = j + y;
if (X < 0 || Y < 0 || X > (height - 1) || Y > (width - 1))
{
continue;
}
totalRed += image[X][Y].rgbtRed;
totalGreen += image[X][Y].rgbtGreen;
totalBlue += image[X][Y].rgbtBlue;
counter++;
}
tmp[i][j].rgbtRed = round(totalRed / counter);
tmp[i][j].rgbtGreen = round(totalGreen / counter);
tmp[i][j].rgbtBlue = round(totalBlue / counter);
}
}
}
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
image[i][j].rgbtRed = tmp[i][j].rgbtRed;
image[i][j].rgbtGreen = tmp[i][j].rgbtGreen;
image[i][j].rgbtBlue = tmp[i][j].rgbtBlue;
}
}
return;
}