Poor man's valgrind

pmvg.c

// "Poor man's valgrind"
#include "pmvg.h"
#include <stdlib.h>
#include <search.h>
static void *track_tree;
struct track_pair {
    void *addr;    size_t size;
};

static long bytes_lost;

static int track_pair_finder(const void *a, const void *b)
{
    return b - a;
}

void *track_malloc(size_t size)
{
    void *addr = malloc(size);

    struct track_pair **where = tsearch(addr, &track_tree, track_pair_finder);
    *where = malloc(sizeof **where);
    (*where)->addr = addr;
    (*where)->size = size;

    return addr;
}

void *track_realloc(void *addr, size_t size)
{
    if (addr)
        tdelete(addr, &track_tree, track_pair_finder);

    void *ptr = realloc(addr, size);

    struct track_pair **where = tsearch(ptr, &track_tree, track_pair_finder);
    *where = malloc(sizeof **where);
    (*where)->addr = ptr;
    (*where)->size = size;

    return ptr;
}

void track_free(void *addr)
{
    free(addr);

    //struct track_pair **where =
    tdelete(addr, &track_tree, track_pair_finder);
    //free(*where);
    //*where = NULL;
}

static void treewalker(const void *nodep, const VISIT which, const int depth)
{
    struct track_pair * const *what = nodep;
    if (which == postorder)
        bytes_lost += (*what)->size;
}

long track_byteslost(void)
{
    bytes_lost = 0;
    twalk(track_tree, treewalker);
    return bytes_lost;
}

pmvg.h

#include <stddef.h>

void *track_malloc(size_t size);
void *track_realloc(void *addr, size_t size);
void track_free(void *addr);
long track_byteslost(void);

Be aware that this implementation leaks memory of its own, which it does not track.

First revision had illegal reads and was pretty much completely wrong. This version still shouldn't be trusted.