11/14/94

  DEBUG_MALLOC.C

/*               debug_malloc.c

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|      | NOTE:  The information in this document has NOT been     |
|      | verified for AIX 4.1.                                    |
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       +----------------------------------------------------------+
 
*/
/*
*********** NOTE: NOT SUPPORTED BY IBM *********************
***  This module is supplied as-is; feel free to make whatever
***  changes you so desire to it.  It is relatively simple
***  so that it can be placed into your situation without too
***  much hassle on your part.  

  This document applies to AIX 3.2.

  debug_malloc(size_t size):  returns a buffer of size bytes 
  by calling malloc, and storing the address into a linked list 
  so that future calls to malloc can check to see if the boundary
  of the buffer is overwritten.  
  debug_realloc(void *ptr, size_t size): returns a new structure 
  of size bytes long in which the MIN(length of first allocation,
  size) bytes of memory are transferred to the new address.
  debug_free(void *ptr):  Frees the memory and removes that block
  from the linked list as well.
  While debugging, the check_pointers() routine may be called to
  see if a buffer has been overflowed.  It returns 0 if there has
  been a buffer overrrun.

  compile all other modules with

  cc -c -Dcalloc=debug_calloc -Dmalloc=debug_malloc \
        -Drealloc=debug_realloc -Dfree=debug_free myfile.c

*/  

/* provides: debug_malloc, debug_calloc, debug_free, check_pointers, */

/* external FUNCTIONS:  malloc(), realloc(), free() */

#ifdef malloc
#undef malloc
#endif
#include <stdio.h>
#include <malloc.h>

#define EXTRA_BUFFER (128)
#define FILL_BUFFER  (' ')
#define MIN(a,b) ((a < b) ? a : b)
#define MAX(a,b) ((a > b) ? a : b)
void * bad_pointer;
int went_over = 0;

struct mem_pointers 
{
  char * pointer;     /* points to a malloc'ed buffer */
  size_t size_of_mem; /* size of buffer originally asked for */
  struct mem_pointers *next_pointer; /* next item on list */
} *first_pointer = NULL; /* got to have someplace to start */

typedef struct mem_pointers mem_p;

int  check_pointers();
void add_pointer(void *ptr, size_t Size, mem_p **pointers);

void *debug_malloc(size_t Size)
{
  void *rc;
  static int opt_set = 0;
  
  if (! opt_set)
      mallopt(1,0); /* call the yorktown malloc() */
  opt_set = 1; 
  (void) check_pointers();
  rc = malloc(Size + EXTRA_BUFFER + 4);/* Size + a buffer + 4 */
  if (rc != NULL)
        add_pointer( rc, Size, &first_pointer);/* add to the list */
  else
        return NULL;
  
  fprintf(stderr,"Fullfilled a request for %d bytes\n",Size);

  return (rc); /* return a pointer to the malloc'ed memory */
}

mem_p * 
find_pointer(mem_p * fp, void * ptr) /* return the mem_p of the pointer */
{                                    /* that has been previously malloc'd */
   mem_p *p = fp;

   while (p && p->pointer != ptr)
        p = p-> next_pointer;
   return (p);
}

remove_pointer(mem_p * mp) /* return the mem_p of the pointer */
{                                    /* that has been previously malloc'd */
   mem_p *p;

   if (first_pointer == mp)
   {
        first_pointer = mp->next_pointer;
   }
   else
   {
        p = first_pointer;

        while (p && p->next_pointer != mp)
                p = p->next_pointer;
        if (p -> next_pointer == mp)
                p-> next_pointer = mp->next_pointer;
   }

   free(mp->pointer);
   free (mp);
}



void * debug_realloc( void * ptr, size_t new_size)
{
   mem_p *mp;
   void * rc;

   check_pointers();
   if (!(mp = find_pointer(first_pointer,ptr))) /* if we don't have the */
 {      fprintf(stderr,"ERROR: realloc called with a bad pointer %x \n", ptr);
        return NULL;
 }
   
   fprintf(stderr,"request to reallocate to %d up from %d\n",
                new_size, mp->size_of_mem);

   rc = malloc(new_size+EXTRA_BUFFER+4);/* malloc new size + a little xtra */
   memcpy(rc, ptr, MIN(mp->size_of_mem,new_size));/* copy the contents */
   memset(((char *) rc)+new_size, FILL_BUFFER, EXTRA_BUFFER);
   free(mp->pointer);/* free the other pointer */
   mp->pointer = rc; /* set up pointer structures */
   mp->size_of_mem = new_size;
}

void *
debug_calloc(size_t a, size_t num)
{
        int counter = 0;
        char *s, *r;

        s = r = debug_malloc(a * num);
        while (counter < a * num)
                *(r++) = '\0';  
        
        return (s);
}

void
debug_free(void *addr)
{
   mem_p *mp;
   mem_p *prev;

   if ((mp = find_pointer(first_pointer,addr)) == NULL)
        {
        free( addr );
        return;
        }
        remove_pointer(mp);
}
   

/* check_pointers(): returns false (0) if there is a corrupted
   buffer, TRUE (1) otherwise
*/

int  check_pointers()
{
  char *s, *r;
  mem_p * p;
  int rc1 = 1, rc = 1 ;

  p = first_pointer;
  while (p)
  {



    rc = 1;
    s = (char *) p -> pointer;
    s += p->size_of_mem;
    r = s + EXTRA_BUFFER;
    while (s < r && rc)
        if (*(--r) != FILL_BUFFER)
        { 
          rc = 0;
          rc1 = 0;
          bad_pointer = p->pointer;
          went_over = r - s +1;
          fprintf(stderr, 
       "\nError: bad block %x, %d too many bytes written to it. size is %d\n",
              bad_pointer, went_over, p-> size_of_mem);
        }
      p = p->next_pointer;
  }  
  return (rc1);
}
  
void add_pointer(void *ptr, size_t Size, mem_p **pointers)
{
  char *s, *r;
  mem_p *p;

  s = (char *) ptr;
  s += Size;
  r = s + EXTRA_BUFFER;
  while (s < r)
      *(s++) = FILL_BUFFER;
  if (*pointers == NULL)
  {
    * pointers = malloc (sizeof (mem_p));
    p = *pointers;
  }
  else
  {
    p = *pointers;
    while (p->next_pointer)
        p = p->next_pointer;
    
    p -> next_pointer =  malloc (sizeof (mem_p));
    p = p->next_pointer;
  }
  p->pointer = ptr;
  p->size_of_mem = Size;
  p->next_pointer = NULL;
}

 









                                                         11/14/94
 
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  END OF DOCUMENT (debug.malloc.c.lng)