Very Simple Malloc

malloc.c

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

#include "malloc.h"
#include "chunk.h"

/* Globals */
Chunk* chunks; 
void* mem_start;

void new_chunk(Chunk*, size_t);

Chunk* find_last_chunk() {
    Chunk* temp_chunk = chunks;

    while (temp_chunk->next) {
        temp_chunk = temp_chunk->next;    
    }

    return temp_chunk;
}

void* xmalloc(size_t size) {

    Chunk* new_address = 0;
    Chunk* temp_chunk;

    // Get next free address (end of LList)
    temp_chunk = find_last_chunk();    

    new_address = temp_chunk + temp_chunk->size + 1;
   
    Chunk* n_chunk = (Chunk*) new_address;
    new_chunk(n_chunk, size);

    temp_chunk->next = n_chunk;

    // Return this address
    return(new_address + sizeof(Chunk));
}

void new_chunk(Chunk* chunk, size_t sz) {

    chunk->size = sz;
    chunk->on = 1;
    chunk->next = 0;
}

int main(int argc, char** args) {

    int memsize = 1024*1024*1024;

    // Assign memory
    mem_start = sbrk(memsize);
    printf("Memstart: %p\n", mem_start);
    
    chunks = 0;
    chunks = mem_start;
    new_chunk(chunks, 0);

    printf("Made it this far\n");

    int* tests[200];
    int i;
    for (i = 0; i < 200; i++) {
      tests[i] = xmalloc(sizeof(int));  
      *tests[i] = i;
    }

    for (i; i >= 0; i--) {
        printf("%d ", *tests[i]);
    }
    printf("\n");

    // Free all the memory
    sbrk(-memsize);

    return 0;
}