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POInitialize double pointer of structs
 

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  1. POInitialize double pointer of structs
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    <p>I am trying to have an array of pointers to generic linked lists within a generic hash table be allocated dynamically with the size being dependent on user input. Please let me show you the code. </p> <p>This is the driver, the user would input the size that they want the hash table to be which correlates directly to how many linked lists there should be in the hash table.</p> <pre><code>int main(int argc, char **argv) { int i; int n; int count; unsigned int seed=0; HashObjectPtr job; HashTablePtr table; if (argc &lt; 2) { fprintf(stderr, "Usage: %s &lt;table size&gt; [&lt;test size=table size * 10&gt;]); exit(1); } n = atoi(argv[1]); count = n; if (argc &gt;= 3) { count = atoi(argv[2]); count *= 10; } if (argc == 4) { seed = atoi(argv[3]); } char * firstInput = (char *)malloc(sizeof(char) * strlen("I'm a void star made at the beginning") + 1); firstInput = strcpy (firstInput, "I'm a void star made at the beginning"); table = createHashTable(n, getKey, toString, freeHashObject, compare); for (i=0; i&lt;n; i++) { job = createHashObject(firstInput); HashInsert(table, job); } runRandomTests(count, seed, n, table); if (DEBUG &gt; 0) PrintHash(table); free(firstInput); FreeHashTable(table); exit( } </code></pre> <p>Here's the struct. I have the array of linked lists defined ListPtr * table => linkedList ** table;</p> <pre><code>typedef struct HashTable HashTable; typedef struct HashTable * HashTablePtr; struct HashTable { int tableSize; int (*getKey)(void *); char * (*toString)(void *); void (*freeHashObject)(void *); Boolean (*compare)(void *, void *); ListPtr * table; }; HashTablePtr createHashTable(int size, int (*getKey)(void *), char * (*toString)(void *), void (*freeHashObject)(void *), Boolean (compare)(void *, void *)); void HashInsert(HashTablePtr table, HashObjectPtr object); HashObjectPtr HashSearch (HashTablePtr table, HashObjectPtr obj); void PrintHash(HashTablePtr table); void FreeHashTable(HashTablePtr table); HashObjectPtr HashRemove(HashTablePtr table, HashObjectPtr obj); int HashFunction(HashObjectPtr obj); </code></pre> <p>This is the function that is initializing the linked lists.</p> <pre><code>HashTablePtr createHashTable(int size, int (*getKey)(void *), char * (*toString)(void *), void (*freeHashObject)(void *), Boolean (*compare)(void *, void *)) { HashTablePtr h = (HashTablePtr)malloc(sizeof(HashTable)); h -&gt; tableSize = size; h -&gt; getKey = getKey; h -&gt; toString = toString; h -&gt; freeHashObject = freeHashObject; h -&gt; compare = compare; h -&gt; table = (ListPtr *)malloc(sizeof(ListPtr)*size); int i; for (i = 0; i &lt; size; i++) { h -&gt; table[i] = createList(getKey, toString, freeHashObject); } } </code></pre> <p>This is the function that creates the linked lists</p> <pre><code>ListPtr createList(int(*getKey)(void *), char * (*toString)(void *), void (*freeHashObject)(void *)) { ListPtr list; list = (ListPtr) malloc(sizeof(List)); list-&gt;size = 0; list-&gt;head = NULL; list-&gt;tail = NULL; list-&gt;getKey = getKey; list-&gt;toString = toString; list-&gt;freeObject = freeHashObject; return list; } </code></pre> <p>I stepped through this in the debugger in eclipse and it's compiling and running fine but when I am clicking on the "table" variable within h during the CreateHashTable function, everything looks fine, the loop iterates through and createsLists at each index. But when I go to insert, I get a segfault.</p> <p>It has to be with the way I am initializing the array of ListPointers but I couldn't think of a better way to do. </p> <p>Help please?</p> <p>Thank you</p>
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    1. PTQuestion
    1. This table or related slice is empty.
    1. USHypothetical inthe Clavicle
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    1. This table or related slice is empty.
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    1. COWhich line causes the segfault? And can you show the definition of `ListPtr`?
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      1. POInitialize double pointer of structs
      1. USluser droog
    2. COThe list is as follows: typedef struct list List; typedef struct list * ListPtr; struct list { int size; NodePtr head; NodePtr tail; int (*getKey)(void *); char * (*toString)(void *); void (*freeObject)(void *); }; the line that causes the segfault is in main at HashInsert(table, job); That function looks like this: void HashInsert(HashTablePtr table, HashObjectPtr object) { int key = HashFunction(getKey(object), table -> tableSize); addAtRear(table -> table[key], createNode(object)); }
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      1. POInitialize double pointer of structs
      1. USHypothetical inthe Clavicle
    3. COI don't know. It's really hard to tell without seeing a complete program. The only thing I can see is that here you call HashFunction with 2 arguments but above it's defined to take 1.
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      1. POInitialize double pointer of structs
      1. USluser droog
 

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