I try to use a new struct for a dynamic "MapNode"s array, yet the program crashes:
Unhandled exception at 0x000C191C in Astar.exe: 0xC0000005: Access violation reading location 0xCCCCCCCC.
I call the getConnectedNodesArray function, which calls the other two functions.
I know it's some kind of pointers problem.
When I used copies of the data instead of trying to point to existing data in MapNode map[][12] it worked.
Thanks.
typedef struct MapNode * MapNodePointer;
typedef struct MapNode{
int x;
int y;
int value;
int traversable;
double f;
double g;
double h;
MapNodePointer parentNode;
}MapNode;
typedef struct MapNodesArray{
MapNode* nodes;
int size;
}MapNodesArray;
void addNodeToEnd(MapNodesArray* arr, MapNode* p) {
arr->size++;
arr->nodes = realloc(arr->nodes, arr->size * sizeof(MapNode*));
(&(arr->nodes))[arr->size - 1] = p;
}
MapNodesArray* NewNodesArr() {
MapNode *first = realloc(NULL, 0 * sizeof(MapNode));
MapNodesArray temp = { first, 0 };
return &temp;
}
MapNodesArray* getConnectedNodesArray(MapNodePointer node, MapNode map[][12]) {
MapNodesArray* arr = NewNodesArr();
addNodeToEnd(&arr, &map[node->x - 1][node->y - 1]);
return arr;
}
You seem to fear indirection. Face it head-on and make sure you get exactly the amount you want:
typedef struct MapNode * MapNodePointer;
The above is a bad idea, because it hides the pointer-ness.
typedef struct MapNodesArray{
MapNode* nodes;
int size;
}MapNodesArray;
The above structure is no good for storing a dynmaic list of pointers to nodes. The nodes-member needs one more star: MapNode** nodes;
void addNodeToEnd(MapNodesArray* arr, MapNode* p) {
arr->size++;
arr->nodes = realloc(arr->nodes, arr->size * sizeof(MapNode*));
There's a better way to indicate the amount of memory you need: arr->size * sizeof *arr->nodes Always check for allocation failure. Bare-bones would be aborting the program. Insert here:
if(!arr->nodes) abort();
The compiler will rightfully complain about the next line now, just remove the address-of-operator:
(&(arr->nodes))[arr->size - 1] = p;
}
MapNodesArray* NewNodesArr() {
MapNode *first = realloc(NULL, 0 * sizeof(MapNode));
The above line could be replaced with MapNode* first = 0;
MapNodesArray temp = { first, 0 };
The above line defines an automatic variable, never return a pointer to that.
return &temp;
}
oops. Complete rewrite:
MapNodesArray* NewNodesArr() {
MapNodesArray temp* = malloc(sizeof *temp);
*temp = (MapNodesArray){ 0, 0 };
return temp;
}
Or even better:
MapNodesArray NewNodesArr() {
return (MapNodesArray){ 0, 0 };
}
Exactly how much memory do you think
MapNodesArray* NewNodesArr() {
MapNode *first = realloc(NULL, 0 * sizeof(MapNode));
MapNodesArray temp = { first, 0 };
return &temp;
}
will allocate? (hint: none at all.)
Also, you're returning a pointer to a local variable (via &temp). That thing dies with the function return.
Agree with what EOF has said, also the line
(&(arr->nodes))[arr->size - 1] = p;
in function addNodeToEnd, will be writing the address p in a memory location outside the the nodes array. This will lead to memory corruption.
to illustrate
say variable 'nodes' has a memory address 0x00000002 and you have assigned a memory location say 0x00000050 through the call to realloc. The statement above takes the offset (arr->size-1) from 0x00000002 instead of taking it from 0x00000050. This is because you are taking the address of nodes by using &. Something of the form
(arr->nodes)[arr->size - 1] = p;
will take the offset from 0x00000050 which is what you seem to be needing.
Related
I have encountered a strange behavior of memory allocation with string-functions.
Note: right now i am told to ignore failure of the allocation operation.
My code is:
void string_reallocation(char *result, int result_length) {
char *temp_result = malloc((strlen(result) + 1) * sizeof(char));
strcpy(temp_result, result);
realloc(result, (result_length + 1) * sizeof(char));
strcpy(result, temp_result);
free(temp_result);
}
this function is called with iterations within a while loop:
while (current_node != NULL) {
current_value_to_string = current_node->toStringFunc(current_node->value);
current_value_length = (int) strlen(current_value_to_string);
current_length += current_value_length + arrow_length;
string_reallocation(result, current_length);
strcat(result, current_value_to_string);
strcat(result, arrow);
current_node = current_node->next;
}
current_node is of type Node as follows:
typedef struct t_node {
Element value;
struct t_node *next;
elementDestroy destroyFunc;
elementCopy copyFunc;
elementToString toStringFunc;
} *Node;
The thing is, for some reason, specifically on the third iteration the free(temp_result); fails with a segmentation fault.
I'm don't think that the while loop has anything to do with the segmentation fault but i put it here in case it does.
This is a biphasic solution, since you got to understand how to use realloc(), by checking on its prototype. Let's do just that first.
Change this:
realloc(result, (result_length + 1) * sizeof(char));
to this:
result = realloc(result, (result_length + 1) * sizeof(char));
since from the reference, we got for the prototype of this method:
Return value: A pointer to the reallocated memory block, which may be
either the same as ptr or a new location.
Now, think about the scope of your variables (pointers). As #whozCraig commented, result = (in the corrected realloc()) assigns a value to an automatic variable. The original result passed in caller-side is unchanged, and now dangling. This has to be handled with an in/out arg or a function return result.
So what you could do, is to simply return that pointer, by changing this:
void string_reallocation(char *result, int result_length) {
to that:
char* string_reallocation(char *result, int result_length) {
// ...
return result;
}
and then change the call to this function, to this:
result = string_reallocation(result, current_length);
I am trying to make an implementation of an n-ary tree in C. When running it I get the following error:
sibling(1143,0x7fff7e925000) malloc: *** error for object 0x7f946b4032c8: incorrect checksum for freed object - object was probably modified after being freed.
*** set a breakpoint in malloc_error_break to debug
Abort trap: 6
I am unsure what is causing the error. As it says it seems that I am writing to an object that was freed. But in my code I do not free any of the memory allocated. I am new to c to this confused me very much. I tried debugging with gdb and it says the error is caused by the printTree(); call in main where I am recursively trying to print the tree. Hope you can help me understand the issue :-).
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct {
char *name;
unsigned int utility;
unsigned int probability;
} Child;
typedef struct {
unsigned int level;
unsigned int player;
unsigned int nChildren;
Child *children;
} Data;
typedef struct sNaryNode{
Data *data;
struct sNaryNode *kid;
struct sNaryNode *sibling;
} NaryNode;
NaryNode* createNode(Data data){
NaryNode *newNaryNode = malloc(sizeof (NaryNode*));
newNaryNode->sibling = NULL;
newNaryNode->kid = NULL;
newNaryNode->data = &data;
return newNaryNode;
}
NaryNode* addSibling(NaryNode* n, Data data){
if(n == NULL) return NULL;
while(n->sibling)
n = n->sibling;
return (n->sibling = createNode(data));
}
NaryNode* addChild(NaryNode* n, Data data){
if(n == NULL) return NULL;
else if(n->kid)
return addSibling(n->kid, data);
else
return (n->kid = createNode(data));
}
void printTree(NaryNode* n) {
if(n == NULL) return;
if(n->sibling) {
printf("%u %u %u %u %u %s", n->data->level, n->data->player, n->data->nChildren, n->data->children[0].probability, n->data->children[0].utility, n->data->children[0].name);
printTree(n->sibling);
}
else if(n->kid) {
printf("%u %u %u %u %u %s", n->data->level, n->data->player, n->data->nChildren, n->data->children[0].probability, n->data->children[0].utility, n->data->children[0].name);
printTree(n->kid);
}
else {
printf("The tree was printed\n");
}
}
int main(void) {
NaryNode *root = calloc(1, sizeof(NaryNode));
Data data;
data.level = 1;
data.player = 1;
data.nChildren = 2;
data.children = calloc(data.nChildren, sizeof data.nChildren);
data.children[0].probability = 50;
data.children[0].utility = 1;
data.children[0].name = "Kom med det første tilbud (anchor)";
data.children[1].probability = 50;
data.children[1].utility = 1;
data.children[1].name = "Afvent modspilleren kommer med første tilbud";
*root = *createNode(data);
int i = 0;
for(i=0; i<root->data->nChildren; i++) {
addChild(root, data);
}
printTree(root);
}
There are various errors in your code.
Allocating an incorrectly sized memory block :
data.children = calloc(data.nChildren, sizeof data.nChildren);
data.children is an array of Child structures, yet you're allocating structures whose size is equal to sizeof(unsigned int), due to data.nChildren being an unsigned int.
Taking the address of a temporary variable and storing it for later usage :
NaryNode* createNode(Data data){
newNaryNode->data = &data;
}
data in createNode only exists for as long as the function is running : in this case, you're taking the address of the local variable data and storing it in the structure that you're returning for later usage. This is a very bad idea, since this pointer will refer to an object that doesn't exist anymore after the function returns.
Keep in mind that you don't need to pass a copy of the Data object into createNode in your current code, since there is really only one Data object in the whole program. Thus, you can change the prototype of createNode to createNode(Data* data), and pass the address of the Data structure that you create in main. Doing anything more involved than that, though, would require deep-copying the structure, I think.
Incorrectly managing the objects' lifetime.
NaryNode *root = calloc(1, sizeof(NaryNode));
*root = *createNode(data);
createNode returns an NaryNode*. However, you never actually assign it to an NaryNode* so that you can free it later. Instead, the pointer to the object that the function returns is known only during the *root = *createNode(data) invocation, and irrevocably lost later on. You do, however, retain the contents of the object due to dereferencing it and copying it into root : the object itself, however, as returned from createNode, is lost and not recoverable, unless pointers to it still exist in the tree.
Here is another problem. This line does not allocate space for a NaryNode, but only for a pointer to a NaryNode:
NaryNode *newNaryNode = malloc(sizeof (NaryNode*));
I'm doing a school assignment, I've I've run into 2 problems. I have to simulate stacks, with arrays.
My current code is as follows:
#include <stdlib.h>
#include <stdio.h>
typedef struct {
int capacity;
int * array;
int size;
} stack_tt;
int pop(stack_tt * stack_p);
void push(stack_tt * stack_p, int value);
int top(stack_tt * stack_p);
stack_tt * newStack(void);
int empty(stack_tt * stack_p);
int main() {
stack_tt * myStack = newStack();
push(myStack, 123);
push(myStack, 99);
push(myStack, 4444);
while (!empty(myStack)) {
int value;
value = pop(myStack);
printf("popped: %d\n", value);
}
return 0; }
stack_tt * newStack(){
stack_tt * newS = malloc(sizeof(stack_tt) * 20);
(*newS).capacity = 1;
(*newS).size = 0;
return newS;
}
void push(stack_tt * stack_p, int value){
if ((*stack_p).size >= (*stack_p).capacity) {
(*stack_p).capacity*=2;
//realloc(stack_p, stack_p->capacity * sizeof(stack_tt));
}
(*stack_p).array = &value;
(*stack_p).size++;
}
int pop(stack_tt * stack_p){
(*stack_p).size--;
int fap = *(*stack_p).array;
return fap;
}
int empty(stack_tt * stack_p){
if ((*stack_p).size >= 1)
return 0;
return 1;
}
Fist of, when I call the line
while(!empty(myStack))
It changes the value in my array to 1.
secondly I'm not able to change individual values in my array, whenever I try things like:
(*stack_p).array[0] = value;
It doesn't know where in the memory to look.
I hope someone is able to help me out :)
There are a couple of problems with the code as I see it.
Lets take the push function where you do
(*stack_p).array = &value;
That will make the array structure member point to the local variable value, and once the function returns the variable cease to exist leaving you with a stray pointer and using that pointer will lead to undefined behavior.
The second problem with that code is that your stack will only be pointing (illegally) to the last element added.
You must allocate memory explicitly for array and use capacity to keep track of how much memory is allocated. The use size as an index into the allocated array for the pushing and popping. Something like
stack_tt * newStack(){
stack_tt * newS = malloc(sizeof(stack_tt)); // Only allocate *one* structure
newS->capacity = 0; // Start with zero capacity
newS->size = 0;
newS->array = NULL;
return newS;
}
void push(stack_tt * stack_p, int value){
if (stack_p->size + 1 > stack_p->capacity){
// Increase capacity by ten elements
int new_capacity = stack_p->capacity + 10;
int * temp_array = realloc(stack_p->array, new_capacity * sizeof(int));
if (temp_srray == NULL)
return;
stack_p->capacity = new_capacity;
stack_p->array = temp_array;
}
stack_p->array[stack_p->size++] = value;
}
int pop(stack_tt * stack_p){
if (stack_p->size > 0)
return stack_p->array[--stack_p->size];
return 0;
}
int empty(stack_tt * stack_p){
return stack_p->size == 0;
}
There is no need to allocate space for 20 structs of type stack_tt, you only need to allocate space for one:
stack_tt * newS = malloc(sizeof(stack_tt));
however you need to allocate space for elements of the struct member array:
newS->array = malloc( sizeof(int)*20);
newS->size = 0;
newS->capacity = 20;
now you can use the array member.
When you push a value to the 'stack', you shouldn't overwrite the array member with the address of the local variable, that doesn't make sense and will cause undefined behavior in addition of loosing the previously allocated memory. Instead simply assign the value to the member array, in the function push:
stack_p->array[stack_p->size] = value;
stack_p->size++;
Similarly when you pop an element, take the current element from the member array:
stack_p->size--;
int fap = stack_p->array[stack_p->size];
The rest of the functions and code should be fixed in the same manner.
You're code is good, but probably you didn't understand the usage of realloc:
//realloc(stack_p, stack_p->capacity * sizeof(stack_tt));
This function returns a pointer to the newly allocated memory, or NULL if the request fails.
The realloc (as the function suggests) takes the memory pointed by the pointer you pass, and copies that memory block in a new and resized block. So the right code should be.
stack_p->array = realloc(stack_p->array, stack_p->capacity * sizeof(stack_tt));
This other line is wrong:
(*stack_p).array = &value;
Change it with:
stack_p->array[stack_p->size] = value;
Another little suggestion, every (*stack_p). can be replaced by stack_p->, which is more elegant.
In the newStack() you're mallocing 20 structs which is kinda useless. You just need one.
Then you should malloc the array for the first time:
newS->array = malloc(sizeof(int));
newS->capacity = 1;
For those experienced with C, this will be a simple memory allocation/referencing problem:
Here are my data structures:
struct configsection {
char *name;
unsigned int numopts;
configoption *options;
};
typedef struct configsection configsection;
struct configfile {
unsigned int numsections;
configsection *sections;
};
typedef struct configfile configfile;
Here are my routines for initializing a configsection or configfile, and for adding a configsection to a configfile:
// Initialize a configfile structure (0 sections)
void init_file(configfile *cf) {
cf = malloc(sizeof(configfile));
cf->numsections = 0;
}
// Initialize a configsection structure with a name (and 0 options)
void init_sec(configsection *sec, char *name) {
sec = malloc(sizeof(configsection));
sec->numopts = 0;
sec->name = name;
printf("%s\n", sec->name);
}
// Add a section to a configfile
void add_sec(configfile *cf, configsection *sec) {
// Increase the size indicator by 1
cf->numsections = cf->numsections + 1;
// Reallocate the array to accommodate one more item
cf->sections = realloc(cf->sections, sizeof(configsection)*cf->numsections);
// Insert the new item
cf->sections[cf->numsections] = *sec;
}
I believe my problem originates in my init_sec() function. Here is an example:
int main(void) {
// Initialize test configfile
configfile *cf;
init_file(cf);
// Initialize test configsections
configsection *testcs1;
init_sec(testcs1, "Test Section 1");
// Try printing the value that should have just been stored
printf("test name = %s\n", testcs1->name);
Although the printf() in init_sec() successfully prints the name I just stored in the configsection, attempting the same thing in the printf() of main() produces a segmentation fault. Further, addsec() produces a segmentation fault.
This routine should be
void init_file(configfile **cf) {
*cf = malloc(sizeof(configfile));
(*cf)->numsections = 0;
(*cf)->sections = NULL; // You forgot to initialise this.
}
i.e. called by init_file(&myconfigfilepointer); so the malloc return value gets passed back.
Need to do the same trick for init_sec
This function is incorrect - here is a corrected version
void add_sec(configfile *cf, configsection *sec) {
// Increase the size indicator by 1
// Reallocate the array to accommodate one more item
cf->sections = realloc(cf->sections, sizeof(configsection)*(1 + cf->numsections));
// Insert the new item
cf->sections[cf->numsections] = *sec; // Since arrays start at 0
cf->numsections = cf->numsections + 1;
}
You then need to adjust the calls in main
At no point do you initialise cf->sections, which means when you try to realloc it the first time, you're passing rubbish. Adding:
cf->sections = NULL;
to init_file should help.
You're also not checking any return codes, but you knew that yes?
You need to pass a pointer of the value to be updated... eg:
// Initialize a configfile structure (0 sections)
void init_file(configfile **cf) {
*cf = malloc(sizeof(configfile));
(*cf)->numsections = 0;
}
configfile *var;
init_file(&var);
printf("%d\n", var->numsections);
Otherwise you are just updating the local pointer *cf and not the original passed in value
You need to really rethink how function arguments are passed in C and what pointers are. Your problem has nothing to do with memory allocation. Rather, your code is assigning a pointer to dynamically allocated memory only to a local variable, of which the calling code knows nothing.
While you could solve the problem by passing a pointer to the caller's pointer (i.e. a double pointer), this is not necessarily the most elegant or most usual way of handling things. Rather, you should return the result of the allocation from the function. While you're at it, you should also use calloc to zero out the memory right away. Wrapping it all up:
typedef struct substuff_
{
int a;
double b;
} substuff;
typedef struct stuff_
{
unsigned int n;
substuff * data;
} stuff;
substuff * init_substuff()
{
substuff * const p = malloc(sizeof *p);
if (p) { p->a = 5; p->b = -0.5; }
return p;
}
stuff * init_stuff()
{
substuff * const p = init_substuff();
if (!p) return NULL;
stuff * const q = malloc(sizeof *q);
if (q) { q->n = 10; q->data = p; }
return q;
}
As an exercise, you should write the corresponding functions void free_substuff(substuff *) and void free_stuff(stuff *).
Yes, there is a problem in init_sec
// Initialize a configsection structure with a name (and 0 options)
void init_sec(configsection *sec, char *name) {
sec = malloc(sizeof(configsection));
sec->numopts = 0;
sec->name = name;
printf("%s\n", sec->name);
}
You're just copying the name pointer here, which means, that it points to the original storage of name. If you'd call init_sec like this
configsection foobar()
{
configsection sec;
char name[80];
get_name(name);
init_sec(sec, name);
return sec;
}
The name pointer became invalid the moment foobar returned. You need to duplicate the string and keep your private copy around. In init_sec:
sec->name = strdup(name);
But there's more. In the very first line of init_sec you're overwriting the pointer that was passed to init_sec with the one of malloc. So the new pointer never gets passed back to the calle. Either use a pointer to a pointer, don't take a configsection pointer at all (after all, you're allocating), but just return the allocated pointer: Complete corrected function:
// Initialize a configsection structure with a name (and 0 options)
configsection* init_sec(char *name) {
configsection *sec = malloc(sizeof(configsection));
sec->numopts = 0;
sec->name = name;
printf("%s\n", sec->name);
return sec;
}
Whew! Long title...here's some pseudo-code to explain that verbiage:
int main(){
int* ptr = function1(); //the data that ptr points to is correct here
function2(ptr);
}
int function2(int* ptr){
//the data that ptr points to is still correct
int i;
for(i=0;i<length;printf("%d\n", (*ptr)[i]), i++); //since ptr points to a contiguous block of memory
function3(ptr);
}
int function3(int* ptr){
//the data that ptr points to is INCORRECT!!!
}
Why would the data in function3 be incorrect?
Note: function1 performs a malloc() and returns the pointer to that memory.
ACTUAL CODE
#include <stdlib.h>
#include <stdio.h>
//Structures
struct hash_table_data_
{
int key, data;
struct hash_table_data_ *next, *prev;
};
struct hash_table_
{
int num_entries;
struct hash_table_data_ **entries;
};
typedef struct hash_table_data_ hash_table_data;
typedef struct hash_table_ hash_table;
//Prototypes
hash_table *new_hash_table(int num_entries);
int hash_table_add(hash_table *ht, int key, int data);
int hash_table_loader(hash_table* ht);
//Main
int main()
{
int num_entries = 8;//THIS MUST BE AUTOMATED
hash_table* ht = new_hash_table(num_entries);
hash_table_loader(ht);
return 0;
}
//Function Definitions
hash_table *new_hash_table(int num_entries)
{
hash_table* ht = (hash_table*) malloc(sizeof(hash_table));
hash_table_data* array = malloc(num_entries * sizeof(hash_table_data));
int i;
for (i=0;i<num_entries;i++)
{
array[i].key = -1;
array[i].data = -1;
array[i].next = NULL;
array[i].prev = NULL;
}
ht->entries = &array;
ht->num_entries = num_entries;
return ht;
}
int hash_table_add(hash_table *ht, int key, int data)
{
//VERIFY THAT THE VALUE ISN'T ALREADY IN THE TABLE!!!!!!!!!!!
int num_entries = ht->num_entries;
hash_table_data* array = *(ht->entries); //array elements are the LL base
int hash_val = key%num_entries;
printf("adding an element now...\n");
printf("current key: %d\n", array[hash_val].key);
int i;
for(i=0;i<num_entries;printf("%d\n", (*(ht->entries))[i].key),i++);//DATA IS INCORRECT!!!!
if (array[hash_val].key == -1)//is this the base link?
{
printf("added a new base link!\n");
array[hash_val].key = key;
array[hash_val].data = data;
array[hash_val].next = NULL;
array[hash_val].prev = &(array[hash_val]);
}
else//since it's not the base link...do stuff
{
hash_table_data* new_link = malloc(sizeof(hash_table_data));
new_link->key = key;//set the key value
new_link->data = data;//set the data value
if (array[hash_val].next == NULL)//we must have the second link
{
printf("added a new second link!\n");
new_link->prev = &(array[hash_val]); //set the new link's previous to be the base link
array[hash_val].next = new_link; //set the first link's next
}
else//we have the 3rd or greater link
{
printf("added a new 3rd or greater link!\n");
hash_table_data next_link_val = *(array[hash_val].next);
while (next_link_val.next != NULL)//follow the links until we reach the last link
{
next_link_val = *(next_link_val.next);//follow the current link to the next
}
//now that we've reached the last link, link it to the new_link
next_link_val.next = new_link; //link the last link to the new link
new_link->prev = &(next_link_val); //link the new link to the last link
}
}
return 0;
}
int hash_table_loader(hash_table* ht)
{
int i;
for(i=0;i<(ht->num_entries);printf("%d\n", (*(ht->entries))[i].key),i++); //DATA IS STILL CORRECT HERE
FILE *infile;
infile = fopen("input.txt", "r");
while(!feof(infile))
{
int key,data;
fscanf(infile, "%d %d", &key, &data);
hash_table_add(ht, key, data);
}
fclose(infile);
}
Note: Issue occurring the first time hash_table_add() is called.
Your first problem is here:
ht->entries = &array;
You cause the structure to hold a hash_table_data** which points to the variable hash_table_data* array which is local to the function; then you exit the function and return a pointer to the structure. The structure still exists (it was allocated via malloc(), and the stuff that array points to still exists, but array itself does not. Accordingly, this pointer within the structure is now invalid.
As far as I can tell, there is no reason for you to be holding a pointer-to-pointer here. Just use hash_table_data* as the entries type, and copy array into that struct member. Pointers are values too.
I guess you iterate incorrectly
for(i=0;i<length;printf("%d\n", (*ptr)[i]), i++);
this is nonsense.
You should rewrite it as this:
for(i=0;i<length;i++)
printf("%d\n", ptr[i]);
(*ptr)[i] is just wrong, it doesn't make sense if you think about it.
*ptr is the first element of the pointed-to array of ints.
ptr[i] is thi ith one, this is what you need.
Please, read Section 6 carefully.
A couple of advises based on this question:
Don't write overcomplicated code like this for statement with comma operator used, it just rarely needed and leads not only to confusion, but to mistakes (although no mistakes with it in this particular example)
Look carefully for mistakes, don't blame everything on functions. If your code doesn't work, try finding the exact place which is wrong and prove it. In this example people who tested your code were right: functions are definitely not the cause of the error.
hash_table *new_hash_table(int num_entries)
{
hash_table* ht = (hash_table*) malloc(sizeof(hash_table));
hash_table_data* array = malloc(num_entries * sizeof(hash_table_data));
// ....
ht->entries = &array; // Problem
// ...
return ht;
} // Life time of array ends at this point.
You are taking the reference of the local variable array and assigning it to ht->entries which is no more valid once the function returns.