dynamically expanding array of struct - c

Question

I am (trying to) write a server-side daemon in c, and it accepts connections from clients. I need a struct that keeps information on each open connection, so I have created an array of my defined struct, and I have it dynamically re-sizing with realloc.
The problem I have is creating the struct within the array. I keep getting this error:
test.c:41: error: conversion to non-scalar type requested
What am I doing wrong?
I spend most of my time in PHP, and am a noob with c. I realize that I am making some simple, beginner mistakes (in other words, feel free to make fun of me). If I am doing something stupid, please let me know. I've put my quality time in with google, but have not figured it out. I have reproduced the issue on smaller scale, as below:
here is my test.h:
typedef struct test_ test;
and here is my test.c:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "test.h"
//define the struct
struct test_ {
int id;
char *ip;
int user;
char *str;
};
//yes, the list needs to be global
test *test_list;
//
// add an item to the global list
//
int add(int id, char *ip, int size)
{
//
// increment size
if(id>size) {
size = id;
//try to expand the list
test *tmp = realloc(test_list,size);
if(tmp) {
//it worked; copy list back
test_list = tmp;
} else {
//out of memory
printf("could now expand list\n");
exit(1);
}
}
//
// HERE IS THE TROUBLE CODE::
test_list[id] = (struct test)malloc(sizeof(test)+(sizeof(int)*5)+strlen(ip)+1);
test_list[id].id = id;
test_list[id].ip = malloc(strlen(ip));
strcpy(test_list[id].ip,ip);
test_list[id].user = 0;
test_list[id].str = NULL;
}
//
// main
//
int main(void)
{
//initialize
int size = 1;
test_list = malloc(size*sizeof(test));
//add 10 dummy items
int i;
for(i=0; i<10; i++) {
size = add(i, "sample-ip-addr", size);
}
//that's it!
return 0;
}

Answer 1

Try changing
test *tmp = realloc(test_list,size);
to
test *tmp = realloc(test_list,size*sizeof(test));
then delete
test_list[id] = (struct test)malloc(sizeof(test)+(sizeof(int)*5)+strlen(ip)+1);
When you allocate for test_list, there's already space for each member of the struct allocated, so you don't need to do it again. You just have to allocate for any pointers within the struct

Answer 2

The return value from 'malloc' is the memory address you've allocated. You can't cast it to a struct. What would that even mean?
You want something like: test_list=realloc(test_list, num_alloc * sizeof(test_));