debug.c

/* Copyright (C) 2000 drscholl@users.sourceforge.net
   This is free software distributed under the terms of the
   GNU Public License.  See the file COPYING for details.

   $Id$ */

/* This is a very simple memory management debugger.  It's useful for detecting
   memory leaks, references to uninitialzed memory, bad pointers, buffer
   overflow and getting an idea of how much memory is used by a program. */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include "debug.h"

#ifdef DEBUG

#define MIN(a,b) ((a<b)?a:b)

/* tunable parameter.  if you have a large amount of memory allocated, setting
   this value higher will result in faster validation of pointers */
#define SIZE 4099

typedef struct _block
{
    void *val;
    int len;
    const char *file;
    int line;
    struct _block *next;
}
BLOCK;

static BLOCK *Allocation[SIZE];
static int Memory_Usage = 0;

void
debug_init (void)
{
    memset (Allocation, 0, sizeof (Allocation));
}

#if SIZEOF_LONG == 8
#define SHIFT 3
#else
#define SHIFT 2
#endif

/* hash the pointer value for insertion into the table */
static int
debug_hash (void *ptr)
{
    int hash;

    /* pointers are allocated on either 4 or 8 bytes boundaries, so we want
       to ignore those values.  this will cause consecutive pointers to hash
       to the next bin */
    hash = ((unsigned long) ptr) >> SHIFT;
    return ((hash & 0x7fffffff) % SIZE);
}

static int
debug_overflow (BLOCK * block, const char *func)
{
    if (*((unsigned char *) block->val + block->len) != END_BYTE)
    {
	fprintf (stderr,
		 "debug_%s: buffer overflow detected in data allocated at %s:%d\n",
		 func, block->file, block->line);
	return 1;
    }
    return 0;
}

static void
debug_exhausted (const char *file, int line)
{
    fprintf (stderr,
	     "debug_malloc(): memory exhausted at %s:%d (%d bytes allocated)\n",
	     file, line, Memory_Usage);
}

void *
debug_malloc (int bytes, const char *file, int line)
{
    BLOCK *block, **ptr;
    int offset;

    if (bytes == 0)
    {
	fprintf (stderr, "debug_malloc(): 0 bytes requested at %s:%d\n",
		 file, line);
	return 0;
    }

    block = malloc (sizeof (BLOCK));
    if (!block)
    {
	debug_exhausted (file, line);
	return 0;
    }
    block->val = malloc (bytes + 1);
    if (!block->val)
    {
	debug_exhausted (__FILE__, __LINE__);
	free (block);
	return 0;
    }
    Memory_Usage += bytes;
    block->len = bytes;
    block->file = file;
    block->line = line;
    memset (block->val, ALLOC_BYTE, bytes);
    *((unsigned char *) block->val + bytes) = END_BYTE;

    offset = debug_hash (block->val);
    for (ptr = &Allocation[offset]; *ptr; ptr = &(*ptr)->next)
    {
	if (block->val < (*ptr)->val)
	    break;
    }
    block->next = *ptr;
    *ptr = block;
    return block->val;
}

void *
debug_calloc (int count, int bytes, const char *file, int line)
{
    void *ptr = debug_malloc (count * bytes, file, line);

    if (!ptr)
	return 0;
    memset (ptr, 0, count * bytes);
    return ptr;
}

static BLOCK *
find_block (void *ptr)
{
    int offset = debug_hash (ptr);
    BLOCK *block;

    for (block = Allocation[offset]; block && ptr > block->val;
	 block = block->next);
    return ((block != 0 && ptr == block->val) ? block : 0);
}

void *
debug_realloc (void *ptr, int bytes, const char *file, int line)
{
    void *newptr;
    BLOCK *block = 0;

    if (bytes == 0)
    {
	debug_free (ptr, file, line);
	return 0;
    }
    if (ptr)
    {
	block = find_block (ptr);
	if (!block)
	{
	    fprintf (stderr,
		     "debug_realloc(): invalid pointer at %s:%d\n", file,
		     line);
	    return 0;
	}
	debug_overflow (block, "realloc");
    }
    newptr = debug_malloc (bytes, file, line);
    if (!newptr)
	return 0;
    if (ptr)
    {
	memcpy (newptr, ptr, MIN (bytes, block->len));
	debug_free (ptr, file, line);
    }
    return newptr;
}

void
debug_free (void *ptr, const char *file, int line)
{
    BLOCK **list, *block = 0;
    int offset;

    if (!ptr)
    {
	fprintf (stderr,
		 "debug_free: attempt to free NULL pointer at %s:%d\n",
		 file, line);
	return;
    }
    offset = debug_hash (ptr);
    if (!Allocation[offset])
    {
	fprintf (stderr,
		 "debug_free: attempt to free bogus pointer at %s:%d\n",
		 file, line);
	return;
    }
    for (list = &Allocation[offset]; *list; list = &(*list)->next)
    {
	if ((*list)->val == ptr)
	    break;
    }
    if (!*list)
    {
	fprintf (stderr,
		 "debug_free: attempt to free bogus pointer at %s:%d\n",
		 file, line);
	return;
    }
    block = *list;
    /* remove the block from the list */
    *list = (*list)->next;

    debug_overflow (block, "free");
    memset (block->val, FREE_BYTE, block->len);
    free (block->val);
    Memory_Usage -= block->len;
    free (block);
}

#if 0
/* display the contents of an allocated block */
static void
debug_dump (BLOCK * block)
{
    int i;

    fputc ('\t', stderr);
    for (i = 0; i < block->len && i < 8; i++)
	fprintf (stderr, "%02x ", *((unsigned char *) block->val + i));
    fputc ('\t', stderr);
    for (i = 0; i < block->len && i < 8; i++)
	fprintf (stderr, "%c",
		 isprint (*((unsigned char *) block->val + i)) ?
		 *((unsigned char *) block->val + i) : '.');
    fputc ('\n', stderr);
}
#endif

void
debug_cleanup (void)
{
    int i;
    BLOCK *block;

    for (i = 0; i < SIZE; i++)
    {
	for (block = Allocation[i]; block; block = block->next)
	{
	    debug_overflow (block, "cleanup");
	    fprintf (stderr, "debug_cleanup: %d bytes allocated at %s:%d\n",
		     block->len, block->file, block->line);
#if 0
	    debug_dump (block);
#endif
	}
    }
    if (Memory_Usage)
	fprintf (stderr, "debug_cleanup: %d bytes total\n", Memory_Usage);
}

char *
debug_strdup (const char *s, const char *file, int line)
{
    char *r;

    r = debug_malloc (strlen (s) + 1, file, line);
    if (!r)
	return 0;
    strcpy (r, s);
    return r;
}

/* check to see if a pointer is valid.  ptr can be an offset into an
 allocation block, so don't use find_block() */
int
debug_valid (void *ptr, int len)
{
    BLOCK *block;
    int offset;

    offset = debug_hash (ptr);
    for(block=Allocation[offset];
	    block && (char*)ptr > (char*)block->val + block->len;
	    block=block->next)
	;
    if (!block)
    {
	fprintf (stderr, "debug_valid: invalid pointer\n");
	return 0;		/* not found */
    }
    /* ensure the pointer is within this block */
    if(ptr<block->val)
    {
	fprintf(stderr,"debug_valid: invalid pointer\n");
	return 0;
    }
    if (debug_overflow (block, "valid"))
	return 0;
    /* ensure that there are at least `len' bytes available */
    return (((char*)ptr + len <= (char*)block->val + block->len));
}

int
debug_usage (void)
{
    return Memory_Usage;
}
#endif /* DEBUG */