Thread: Segmentation fault

Really sorry to post such a long code. But I have no idea where this segmentation fault is coming from.

It prints fine until it calls splitme function and then i get a segementation fault.

Code:

int LineCount(FILE* fptr);
double ReadFile(FILE *filename, int num_lines, double *array);
double *splitme(double *array, size_t *p, size_t *q);
	
int main(void)
{
	size_t	j, encrypt_lines, bfun_lines, p1, q1;
	size_t *p, *q;
	FILE *encrypt, *blurring;
	double *encrypt_array, *bfun_array, *split_array;
	const char input1[]="toencrypt.txt", input2[]="bfun.txt";

	encrypt=fopen("toencrypt.txt","r");	
	blurring=fopen("bfun.txt","r");
	
	if (encrypt ==NULL || blurring == NULL)
    {
	    printf("Cannot open required file!\n");
        printf("Please ensure your data file\n");
	    printf("is in the correct directory\n");
	    exit(EXIT_FAILURE);
	}

	encrypt_lines=LineCount(encrypt);
	printf("%i\n", encrypt_lines); //remove
	bfun_lines=LineCount(blurring);
	printf("%i\n", bfun_lines); //remove
	
	encrypt_array = malloc ((encrypt_lines)*sizeof(double));
	bfun_array = malloc ((bfun_lines)*sizeof(double));
	split_array = malloc ((bfun_lines)*sizeof(double));
	
	*encrypt_array= ReadFile(encrypt, encrypt_lines, encrypt_array);
	*bfun_array= ReadFile(blurring, bfun_lines, bfun_array);
	
	j=0; 
	for(j=0; j<encrypt_lines; j++) 
	{ 
		printf("main encrypt array %i is %lf\n", j, encrypt_array[j]);
	} 
	
	j=0; 
	for(j=0; j<bfun_lines; j++)
	{
		printf("main bfun array %i is %lf\n", j, bfun_array[j]);
	}
	
	fclose(encrypt);
	fclose(blurring);
	
	*p = bfun_lines;
	*q=0;
	
	*split_array= *splitme(bfun_array, p, q);
	
	j=0;
	for (j=0; j<bfun_lines; j++)
	{
		printf("split main array %i is %lf\n", j, split_array[j]);
	}
	
	printf("p is %i\n", p);
	printf("q is %i\n", q);
	
	
	
	return(0);
}

int LineCount(FILE* fptr)
{	
	int count = 0;
	char check[81];
	char temp[81];
	
	while (fgets(temp, sizeof(temp), fptr) != NULL)
	{
		fscanf(fptr, "%s", &check);
		if (check != "\n")
		{
			count++;
		}
	}
	
	count = ((count+1)*2);
	return(count);
}

double ReadFile(FILE *filename, int num_lines, double *array)
{
	int	i;
	
	rewind(filename);
	
	i=0;
	for(i=0; i<(num_lines); i++)
	{
		if((i & 1) == 0)
		{
			fscanf(filename, "%lf", &array[i]);
		}
		else
		{
			array[i]=0.0;
		}	
	}
	
	i=0;
	for(i=0; i<(num_lines); i++)
	{
		printf("array %i is %lf\n", i, array[i]);
	}
	
	
	rewind(filename);
	return(*array);
	free(array);
}

double *splitme(double *array, size_t *p, size_t *q)
{
	size_t i, n, j;
	double sum1, sum2; 
	double *bfun_split, *ptr;
	size_t array_size, centroid;
	
	array_size = *p;
	
	for (i=0; i<array_size; i++)
	{
		sum1 += (i * array[i]);
		sum2 += array[i];
	}
	centroid = (round)(sum1/sum2);
	printf("centroid is %d\n", centroid);
	
	*q = centroid - 1;
	*p = array_size - centroid - 1;
	printf("array size is %i\n", array_size);
	printf("p is %i\n", p);
	printf("q is %i\n", q);
	bfun_split = malloc((array_size)*sizeof(double));
	
	i=0;
	for (i=0; i<*p; i++)
	{
		bfun_split[i] = array[i+centroid];//allocate the right of the centroid
	}
	
	i=0;
	//x=(array_size - q - 1);
	for (i=(array_size - *q - 1); i<array_size; i++)
	{
		bfun_split[i] = array[i-centroid]; //allocate the left of centroid
	}
	
	i=0;
	for (i=0; i<array_size; i++)
	{
		printf("split array %i is %lf\n", i, bfun_split[i]);
	}
	
	free(array);
	array = malloc((array_size)*sizeof(double));
	
	i=0;
	for (i=0; i<array_size; i++)
	{
		array[i] = bfun_split[i];
	}
	
	i=0;
	for (i=0; i<array_size; i++)
	{
		printf("split array normal %i is %lf\n", i, array[i]);
	}
	
	return(array);

}

Compile your code in debug mode and run it in the debugger. It will stop when and where the seg fault occurs.

Thanks...

I used a printf statement to see where the segmentation fault occurred and found it was an uninitialised pointer...

for some reason though...fixing it has led to a complete breakdown in the calculations in splitme!

Code:

i=0;
	for (i=0; i<array_size; i++)
	{
		sum1 += (i * array[i]);
		sum2 += array[i];
	}

is no longer working!!

You're also using uninitialized variables sum1 and sum2 in that function

Code:

size_t i, n, j;
	double sum1, sum2; 
	double *bfun_split, *ptr;
	size_t array_size, centroid;
	
	array_size = *p;
	
	for (i=0; i<array_size; i++)
	{
		sum1 += (i * array[i]);
		sum2 += array[i];
	}

What's the value of sum1 the first time through that loop, before you add the value of (i * array[i]) to it?

Thanks very much for looking through it! I realise how tedious it must be.

@hk;

#1 : I am looking at the location for a \n and incrementing if it is stored. This way of doing it accounts for blank lines within my data file. It seems to be working for me in a variety of situations but I'm not sure if that is luck or not...

#2 : I will be checking for NULL values in the final program...I am currently just trying to get things going...

with return values do you mean the return from the external? What I believe I am doing is passing 2 specific files through a general file reader and returning the resultant array into 2 specific arrays...?

#3 : I did post that this was in fact the problem that caused the segmentation fault and I have fixed this, thanks.

@rags_to_riches;

Yep, I had a look at that and I fixed it by setting sum1 and sum2 to zero before the loop!

Thanks guys for your help, it is now running smoothly!