/* Smartalloc.c       Copyright Clinton Staley 1991
 * 
 * Smartalloc provides an malloc version which checks for several possible
 * errors:
 *
 * 1. Failure of malloc call for any reason
 * 2. Attempt to free memory not allocated by malloc, or already freed.
 * 3. Writing past the end of malloc-ed memory
 * 4. Failure to free memory by some point in the program.
 * 5. Use of data after it has been freed.
 *
 * Use smartalloc by including smartalloc.h in any file that calls malloc
 * or free.  Also, compile smartalloc.c along with your other .c files.
 * If you make any of errors 1-3 above, smartalloc will report the error
 * and the file/line on which it occured.  To find out if you have left
 * memory unfreed, call report_space().  If any unfreed memory is
 * outstanding, report_space will report the number of bytes of unfreed
 * memory.  If no memory is unfreed, report_space remains silent.
 * Use of freed data is "detected" by writing garbage into the freed data,
 * which will usually generate a runtime fault if the data is later used.
 *
 * All rights to this package are reserved by its author.  Duplication of
 * source or object code is permitted only with the author's permission.
 */

#include <stdio.h>
#include <malloc.h>

#define PATTERN 0xA
#define TAIL_BYTES 4

typedef struct track_t {
	char *data;
	int space;
	struct track_t *next;
} track_t;

static track_t *track = NULL;
static int allocated = 0;

char *smartalloc(long bytes, char *file, int line)
{
   track_t *temp;
	char *data;
	int i;

	temp = (track_t *) malloc(sizeof(track_t));
	if ((temp->data = data = malloc(bytes + TAIL_BYTES)) == NULL)
		fprintf(stderr, "Malloc failure in file %s on line %d\n", file, line);
	allocated += bytes;
   for (i = 0; i < TAIL_BYTES; i++)
		data[bytes + i] = PATTERN;
	temp->space = bytes;
	temp->next = track;
	track = temp;
	return data;
}

void smartfree(char *address, char *file, int line)
{
	track_t *temp, *to_free;
	int i;

   if (track == NULL) {
   	fprintf(stderr, 
		 "Attempt to free non-malloced space in file %s at line %d\n",
		 file, line);
	   return;
	}
   if (track->data == address) {
		to_free = track;
		track = track->next;
	} 
	else {
		for (temp = track; temp->next != NULL && temp->next->data != address;)
			temp = temp->next;
		if (temp->next == NULL) {
			fprintf(stderr, 
			 "Attempt to free non-malloced space in file %s at line %d\n",
			 file, line);
		   return;
		}
		to_free = temp->next;
		temp->next = to_free->next;
	}
	for (i = 0; i < TAIL_BYTES; i++)
		if (address[to_free->space + i] != PATTERN) {
			fprintf(stderr, 
			 "Space freed in file %s at line %d has data written past its end.\n",
			 file, line);
			break;
		}
	for (i = 0; i < to_free->space; i++)
		address[i] = PATTERN;
	allocated -= to_free->space;
	free(address);
	free(to_free);
}

int report_space()
{
	if (allocated > 0)
		fprintf(stderr, "Allocated space is %d\n", allocated);
}