Question

I did not expect to be able to increment a pointer to a struct in a memory block of structs. But it seems to work. Is there any case where this does not work? If I create a “list” of structs then I should always be able to increment the pointer to them and C will figure out how many bytes to move by?

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

struct User {
    int id;
    char name[32];
    float net_worth;
};
typedef struct User User;


int main(int argc, char** argv) {
    User* u1 = (User*)malloc(sizeof(User));
    u1->id = 1;
    strcpy(u1->name, "Mike");
    u1->net_worth = 43.45;
    User* u2 = (User*)malloc(sizeof(User));
    u2->id = 2;
    strcpy(u2->name, "Pablo");
    u2->net_worth = -2.00;
    User* u3 = (User*)malloc(sizeof(User));
    u3->id = 3;
    strcpy(u3->name, "Frederick");
    u3->net_worth = 7329213.45;

    User** users = (User**)malloc(sizeof(User)*10);
    *users = u1;
    printf("%s\n", ((User*)(*users))->name);
    *users++;
    *users = u2;
    printf("%s\n", ((User*)(*users))->name);
    *users++;
    *users = u3;
    printf("%s\n", ((User*)(*users))->name);


    return 0;

}

Answer 1

This is very much by design. Assume you have

User userArray[16];

You could either access the second user via userArray[1], or *(userArray + 1), or get a pointer to the first element and increment it via ++.