list - How do I pass a pointer (that points to a structure) to a function? -
i want create linked list in c, when use code below, gcc throws error:
error: invalid type argument of '->' (have 'struct list')
the code is:
#include <stdio.h> #include <stdlib.h> struct list{ int age; struct list *next; }; void create_item(int *total_items, struct list where_is_first_item, struct list where_is_last_item) { struct list *generic_item; generic_item = malloc(sizeof(struct list)); printf("\nage of item %d: ", (*total_items)+1); scanf("%d", &generic_item->age); if(*total_items == 0){ where_is_first_item->next=generic_item; where_is_last_item->next=generic_item; printf("\nitem created\n"); } else{ where_is_last_item->next=generic_item; printf("\nitem created\n"); } int main (void){ struct list *where_is_first_item; struct list *where_is_last_item; int total_items=0; printf("\n\n\tcreate new item\n"); create_item(&total_items, where_is_first_item, where_is_last_item); total_items++; return 0; }
void create_item(int *total_items, struct list *where_is_first_item, struct list *where_is_last_item) add star!
you referencing invalid memory because allocate generic_item reference where_is_first_item. where_is_first_item not allocated to. try where_is_first_item = generic_item; before use where_is_first_item.
you find pointers in main function remain unmodified because pointer values being passed. here gets confusing/interesting: if want pointers in main modified need pass pointers to pointers: struct_list **where_is_first_item. trust me, head in.
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