ting to Generic stack implementation in C with void pointers -

trying implement simple generic stack went trough bunch of stack overflows , segmentation faults wrote this:

#include <stdlib.h> #include <stdio.h>  #define nullptr (void *)0  struct s {     void *content;     struct s *next; }; typedef struct s stack; stack *createstack() {     stack *tmp = (stack *) malloc(sizeof(stack));      tmp->content = nullptr;     tmp->next    = nullptr;      return tmp; }  stack *pushstack(stack *ptr, void *content) {     stack *newstr = createstack();     newstr->content = content;     newstr->next = ptr;     ptr = newstr;     return (ptr); }  stack *popstack(stack *ptr, void *value) {     stack *todelete = ptr;     value = ptr->content;     ptr = ptr->next;     free(todelete);     return (ptr); }  stack *stackhandle = nullptr;  void printstack(stack *ptr) {     int *element;     int i;     for(i=0; <= 20; i++) {         ptr = popstack(ptr, element);         printf("%d ", *element);     }     printf("\n"); }  int main() {     stackhandle = createstack();     int i;     for(i=0; <= 21; i++) {         stackhandle = pushstack(stackhandle, &i);     }     printstack(stackhandle); } 

everything works fails restore int void pointer... analyzing other implementations i'm still not understanding why mine not working. here expecting see 21 times getting instead

0 8240 842539056 842539056 842539056 842539056 842539056 842539056 842539056 842539056 842539056 842539056 842539056 842539056 842539056 842539056 842539056 842539056 842539056 842539056 842539056

for every value of bigger 20 , beautiful segmentation fault if below 20

you aren't allocating space hold actual data, allocating room pointers point elsewhere. that's not useful adt.

what instead create stack holds hard-copies of data:

typedef struct s {     void*     data;     size_t    size;     struct s* next; } stack; 

the functions have changed:

stack *pushstack(stack *ptr, void *data, size_t size); stack *popstack(stack *ptr, void *data, size_t* size); // return data , size 

you instead create item this:

stack *createstack (void* data, size_t size) {     stack *tmp = malloc(sizeof(stack));      tmp->data = malloc(size);     memcpy(tmp->data, data, size);     tmp->size = size;     tmp->next = null;      return tmp; } 

once have changed design above, can start worrying weeding out bugs.