problems with free()

leo mueller <[email protected]> Tue, 28 Apr 2009 11:20:29 +0200

Newsgroups	org.kernel.vger.linux-c-programming
Message-ID	<[email protected]>

hi all,

i got a little problem with free() ... i am allocating mem for a
special struct and putting it afterwards
into a linked list. allocating works fine, but freeing not. i'm
tracking the program with htop. after
allocating, the percentage of mem usage stays constant ...

the test-file is attached.

any help is appreciated. big thanks :)

test.c (text/x-csrc, 3.5 KB)

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

typedef unsigned long long nodeinf;
typedef unsigned long long hashinf;

struct node {
    hashinf hash;
    nodeinf info;
    struct node *parent;
    struct levelcache *childs;
};

struct levelcache {
    unsigned int size;
    unsigned int last;
    struct node **list;
};

struct cache {
    struct levelcache *root;
    struct node *last_node;
};

struct stackframe {
    struct levelcache *lc;
    struct stackframe *next;
};

void release();
inline void push_to_stack(struct levelcache *);
void free_stack();
inline void add_to_list(struct node *);
struct stackframe *sfalloc();
struct node *nalloc();
struct levelcache *lcalloc(int);
void lcrealloc(struct levelcache *, int);

struct stackframe *garbage;

/*
 * Pushes element to garbage stack
 */
inline void push_to_stack(struct levelcache *l)
{
    struct stackframe *sf;

    sf = sfalloc();
    sf->lc = l;
    sf->next = garbage;
    
    garbage = sf;
}
	
/*
 * Frees garbage stack
 */
void free_stack()
{
    int i;
    int j = 0;
    void *rc;
    struct stackframe *sf;
    
    while(garbage != NULL){
        sf = garbage->next;
        
        garbage->next = NULL;
        
        for(i = 0; i < garbage->lc->size; ++i){
            if(garbage->lc->list[i] != NULL){
                j++;
                printf("free adr: 0x%x\n", (unsigned int) garbage->lc->list[i]);
                rc = realloc(garbage->lc->list[i], 0);
                printf("free adr: 0x%x\n", (unsigned int) rc);
            }
        }
        free(garbage->lc->list);
        free(garbage->lc);
        free(garbage);
        
        garbage = sf;
    }
    
    printf("%d elem freed.\n", j);
}

/*
 * Allocation of a stackframe
 */
struct stackframe *sfalloc()
{
    struct stackframe *sf = (struct stackframe *) malloc(sizeof(struct stackframe));
    
    if(!sf){
        fprintf(stderr, "error: malloc stackframe\n");
        release();
        exit(1);
    }

    memset(sf, 0, sizeof(struct stackframe));
    return sf;
}

/*
 * Allocation of a single node
 */
struct node *nalloc()
{
    struct node *n = (struct node *) malloc(sizeof(struct node));
    
    if(!n){
        fprintf(stderr, "error: malloc node\n");
        release();
        exit(1);
    }

    memset(n, 0, sizeof(struct node));
    return n;
}

/*
 * Allocation of a levelcache element
 */
struct levelcache *lcalloc(int n)
{
    int i;
    struct levelcache *l;

    if(!n)
        return NULL;

    l = (struct levelcache *) malloc(sizeof(struct levelcache));

    if(!l){
        fprintf(stderr, "error: malloc levelcache\n");
        release();
        exit(1);
    }
    
    l->list = (struct node **) malloc(sizeof(struct node *) * n);

    if(!l->list){
        fprintf(stderr, "error: malloc node list\n");
        release();
        exit(1);
    }
    
    l->size = n;
    l->last = 0;

    for(i = 0; i < l->size; ++i)
        l->list[i] = NULL;

    return l;
}

/*
 * Drops our whole cache
 */
void release()
{
    free_stack();
}

/*
 * Main routine
 */
int main(int argc, char **argv)
{
    int i, j;
    struct levelcache *l;

    garbage = NULL;

    for(i = 0; i < 200; ++i){
        l = lcalloc(2000);
        
        for(j = 0; j < l->size; ++j){
            l->list[j] = nalloc();
            l->list[j]->hash = j;
            l->list[j]->info = j;
            printf("alloc adr: 0x%x\n", (unsigned int) l->list[j]);
        }
        
        push_to_stack(l);
    }

    release();
    
    sleep(5);
    return 0;
}