I wrote a c program, compiled it and it ran fine. After a few compiles - it started giving me a segmentation fault. I renamed the folder, recompiled and it worked again.
Is this something normal? To have an inconsistent segmentation fault? I change the output name, change folder names etc.. and it bounces from giving segmentation fault to not giving seg fault. I don't know what to do anymore.
I mean, if it is a coding problem, seg fault should be consistent, right? I should get it every time. here's the code:
file my_set.c:
#include <stdio.h>
#include <stdlib.h>
#include "list.h"
/*
The program acceps a set of numbers from stdin until EOF
And then prints them (not storing duplicate numbers)
*/
int main ()
{
int num;
nodePtr head; /*head of the list*/
while (scanf("%d", &num) != EOF)
{
addToList(num, &head);
}
printList(head);
freeList(head);
return 0;
}
file list.c:
#include <stdio.h>
#include <stdlib.h>
#include "list.h"
/*
Implements a linked list, each element of which contains a dynamic array.
I used a linked list to maximize potential memory in case it is fragmented.
I use a dynamic array in each node to minimize the percentage of overhead
from creating a list (the pointer, the index...);
*/
/*
Adds number n to list *h
4 cases:
1. list is empty:
creating one
updating h with new list
creating a new dynamic array in the list
updating it and the index
2. can reallocate current node's array for 1 more int
3. cannot reallocate current node's array:
creating a new node
initializing it
4. cannot create a new node
printing the current list, an "out of memory error" and freeing all memory.
*/
void addToList(int n, nodePtr *h)
{
static nodePtr p; /*points to current last node*/
int *temp; /*for use in reallocation*/
if (!*h) /*first item of set*/
{
*h = malloc (sizeof(node));
(*h)->arr = malloc(sizeof(int));
(*h)->arr[0] = n;
(*h)->i = 1;
p = *h;
return;
}
/*if n is already in the list, no need to add it
the call comes after first item, because first item cannot be in the list*/
if(existsInList(n, *h)) return;
/*using realloc while still possible*/
if ((temp = realloc(p->arr, (p->i+1)*sizeof(int))))
{
p->arr = temp;
p->arr[p->i] = n;
p->i++;
return;
}
/*if realloc no longet possible - start new node*/
if ((p->next = malloc(sizeof(node))))
{
p = p->next;
p->arr = malloc(sizeof(int));
p->arr[0] = n;
p->i = 1;
return;
}
/*can no longer start new nodes - quit with error, after printing*/
printf("out of memory!");
printList(*h);
freeList(*h);
}
/*checks if n is in p assuming p is not null
it can asume so because the call for it comes after the check for first item*/
int existsInList(int n, nodePtr p)
{
int i;
for (; p ; p = p->next)
for (i = 0; i < p->i; i++)
if (p->arr[i] == n)
return 1;
return 0;
}
/*frees the list*/
void freeList(nodePtr p)
{
nodePtr temp = p;
if (!p) return; /*list is empty*/
while (p)
{
free(p->arr);
p = p->next;
free(temp);
}
}
/*prints the content of the list to stdout*/
void printList(nodePtr p)
{
if (!p) return;
int i;
printf("\n");
for (; p ; p = p->next)
for (i = 0; i < p->i; i++)
printf("%d ", p->arr[i]);
printf("\n");
}
file list.h:
/*
pointer to a node
declare a variable of this type to create a list
then start adding to the list
*/
typedef struct s *nodePtr;
/*the struct that represents each node of the list
reason for dynamic array is in "list.c"
*/
typedef struct s
{
int *arr;
int i; /*index for next num, also size of array;*/
nodePtr next;
}node;
/*Adds the int to list at nodePtr omitting duplicates*/
void addToList(int, nodePtr*);
/*prints a list*/
void printList(nodePtr);
/*returns 1 if an int exists in list referenced by nodePtr, 0 otherwise*/
int existsInList(int, nodePtr);
/*frees all dynamically allocated memory*/
void freeList(nodePtr);
Basically all I do is get numbers from stdin, put them in a list(no duplicates) and then print them. I use a list of dynamic arrays.
