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POWhy is this segmentation fault inconsistent across builds?
 

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  1. POWhy is this segmentation fault inconsistent across builds?
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    <p>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.<br> 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.<br> I mean, if it is a coding problem, seg fault should be consistent, right? I should get it every time. here's the code:<br> file my_set.c:</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #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", &amp;num) != EOF) { addToList(num, &amp;head); } printList(head); freeList(head); return 0; } </code></pre> <p>file list.c:</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #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)-&gt;arr = malloc(sizeof(int)); (*h)-&gt;arr[0] = n; (*h)-&gt;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-&gt;arr, (p-&gt;i+1)*sizeof(int)))) { p-&gt;arr = temp; p-&gt;arr[p-&gt;i] = n; p-&gt;i++; return; } /*if realloc no longet possible - start new node*/ if ((p-&gt;next = malloc(sizeof(node)))) { p = p-&gt;next; p-&gt;arr = malloc(sizeof(int)); p-&gt;arr[0] = n; p-&gt;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-&gt;next) for (i = 0; i &lt; p-&gt;i; i++) if (p-&gt;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-&gt;arr); p = p-&gt;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-&gt;next) for (i = 0; i &lt; p-&gt;i; i++) printf("%d ", p-&gt;arr[i]); printf("\n"); } </code></pre> <p>file list.h:</p> <pre><code>/* 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); </code></pre> <p>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.</p>
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