1 /* $RCSfile: malloc.c,v $$Revision: 4.1 $$Date: 92/08/07 18:24:25 $
4 * Revision 4.1 92/08/07 18:24:25 lwall
6 * Revision 4.0.1.4 92/06/08 14:28:38 lwall
7 * patch20: removed implicit int declarations on functions
8 * patch20: hash tables now split only if the memory is available to do so
9 * patch20: realloc(0, size) now does malloc in case library routines call it
11 * Revision 4.0.1.3 91/11/05 17:57:40 lwall
12 * patch11: safe malloc code now integrated into Perl's malloc when possible
14 * Revision 4.0.1.2 91/06/07 11:20:45 lwall
15 * patch4: many, many itty-bitty portability fixes
17 * Revision 4.0.1.1 91/04/11 17:48:31 lwall
18 * patch1: Configure now figures out malloc ptr type
20 * Revision 4.0 91/03/20 01:28:52 lwall
27 static char sccsid[] = "@(#)malloc.c 4.3 (Berkeley) 9/16/83";
33 * malloc.c (Caltech) 2/21/82
34 * Chris Kingsley, kingsley@cit-20.
36 * This is a very fast storage allocator. It allocates blocks of a small
37 * number of different sizes, and keeps free lists of each size. Blocks that
38 * don't exactly fit are passed up to the next larger size. In this
39 * implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long.
40 * This is designed for use in a program that uses vast quantities of memory,
41 * but bombs when it runs out.
47 static int findbucket();
48 static int morecore();
50 /* I don't much care whether these are defined in sys/types.h--LAW */
52 #define u_char unsigned char
53 #define u_int unsigned int
54 #define u_short unsigned short
57 * The overhead on a block is at least 4 bytes. When free, this space
58 * contains a pointer to the next free block, and the bottom two bits must
59 * be zero. When in use, the first byte is set to MAGIC, and the second
60 * byte is the size index. The remaining bytes are for alignment.
61 * If range checking is enabled and the size of the block fits
62 * in two bytes, then the top two bytes hold the size of the requested block
63 * plus the range checking words, and the header word MINUS ONE.
66 union overhead *ov_next; /* when free */
68 double strut; /* alignment problems */
71 u_char ovu_magic; /* magic number */
72 u_char ovu_index; /* bucket # */
74 u_short ovu_size; /* actual block size */
75 u_int ovu_rmagic; /* range magic number */
78 #define ov_magic ovu.ovu_magic
79 #define ov_index ovu.ovu_index
80 #define ov_size ovu.ovu_size
81 #define ov_rmagic ovu.ovu_rmagic
84 #define MAGIC 0xff /* magic # on accounting info */
85 #define OLDMAGIC 0x7f /* same after a free() */
86 #define RMAGIC 0x55555555 /* magic # on range info */
88 #define RSLOP sizeof (u_int)
94 * nextf[i] is the pointer to the next free block of size 2^(i+3). The
95 * smallest allocatable block is 8 bytes. The overhead information
96 * precedes the data area returned to the user.
99 static union overhead *nextf[NBUCKETS];
104 * nmalloc[i] is the difference between the number of mallocs and frees
105 * for a given block size.
107 static u_int nmalloc[NBUCKETS];
112 #define ASSERT(p) if (!(p)) botch("p"); else
118 printf("assertion botched: %s\n", s);
127 register MEM_SIZE nbytes;
129 register union overhead *p;
130 register int bucket = 0;
131 register MEM_SIZE shiftr;
135 MEM_SIZE size = nbytes;
139 if (nbytes > 0xffff) {
140 fprintf(stderr, "Allocation too large: %lx\n", (long)nbytes);
145 if ((long)nbytes < 0)
146 fatal("panic: malloc");
148 #endif /* safemalloc */
151 * Convert amount of memory requested into
152 * closest block size stored in hash buckets
153 * which satisfies request. Account for
154 * space used per block for accounting.
156 nbytes += sizeof (union overhead) + RSLOP;
157 nbytes = (nbytes + 3) &~ 3;
158 shiftr = (nbytes - 1) >> 2;
159 /* apart from this loop, this is O(1) */
163 * If nothing in hash bucket right now,
164 * request more memory from the system.
166 if (nextf[bucket] == NULL)
168 if ((p = (union overhead *)nextf[bucket]) == NULL) {
171 fputs("Out of memory!\n", stderr);
181 # if !(defined(I286) || defined(atarist))
183 fprintf(stderr,"0x%x: (%05d) malloc %ld bytes\n",p+1,an++,(long)size);
186 fprintf(stderr,"0x%lx: (%05d) malloc %ld bytes\n",p+1,an++,(long)size);
189 #endif /* safemalloc */
191 /* remove from linked list */
193 if (*((int*)p) & (sizeof(union overhead) - 1))
194 #if !(defined(I286) || defined(atarist))
195 fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",*((int*)p),p);
197 fprintf(stderr,"Corrupt malloc ptr 0x%lx at 0x%lx\n",*((int*)p),p);
200 nextf[bucket] = p->ov_next;
208 * Record allocated size of block and
209 * bound space with magic numbers.
211 if (nbytes <= 0x10000)
212 p->ov_size = nbytes - 1;
213 p->ov_rmagic = RMAGIC;
214 *((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
216 return ((MALLOCPTRTYPE *)(p + 1));
220 * Allocate more memory to the indicated bucket.
226 register union overhead *op;
227 register int rnu; /* 2^rnu bytes will be requested */
228 register int nblks; /* become nblks blocks of the desired size */
229 register MEM_SIZE siz;
234 * Insure memory is allocated
235 * on a page boundary. Should
236 * make getpageize call?
238 #ifndef atarist /* on the atari we dont have to worry about this */
239 op = (union overhead *)sbrk(0);
242 (void)sbrk(1024 - ((int)op & 0x3ff));
244 /* The sbrk(0) call on the I286 always returns the next segment */
248 #if !(defined(I286) || defined(atarist))
249 /* take 2k unless the block is bigger than that */
250 rnu = (bucket <= 8) ? 11 : bucket + 3;
252 /* take 16k unless the block is bigger than that
253 (80286s like large segments!), probably good on the atari too */
254 rnu = (bucket <= 11) ? 14 : bucket + 3;
256 nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */
259 op = (union overhead *)sbrk(1L << rnu);
264 * Round up to minimum allocation size boundary
265 * and deduct from block count to reflect.
269 op = (union overhead *)(((MEM_SIZE)op + 8) &~ 7);
273 /* Again, this should always be ok on an 80286 */
276 * Add new memory allocated to that on
277 * free list for this hash bucket.
280 siz = 1 << (bucket + 3);
281 while (--nblks > 0) {
282 op->ov_next = (union overhead *)((caddr_t)op + siz);
283 op = (union overhead *)((caddr_t)op + siz);
291 register MEM_SIZE size;
292 register union overhead *op;
293 char *cp = (char*)mp;
297 # if !(defined(I286) || defined(atarist))
299 fprintf(stderr,"0x%x: (%05d) free\n",cp,an++);
302 fprintf(stderr,"0x%lx: (%05d) free\n",cp,an++);
305 #endif /* safemalloc */
309 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
311 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
313 if (op->ov_magic != MAGIC) {
314 warn("%s free() ignored",
315 op->ov_magic == OLDMAGIC ? "Duplicate" : "Bad");
318 op->ov_magic = OLDMAGIC;
321 ASSERT(op->ov_rmagic == RMAGIC);
322 if (op->ov_index <= 13)
323 ASSERT(*(u_int *)((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC);
325 ASSERT(op->ov_index < NBUCKETS);
327 op->ov_next = nextf[size];
335 * When a program attempts "storage compaction" as mentioned in the
336 * old malloc man page, it realloc's an already freed block. Usually
337 * this is the last block it freed; occasionally it might be farther
338 * back. We have to search all the free lists for the block in order
339 * to determine its bucket: 1st we make one pass thru the lists
340 * checking only the first block in each; if that fails we search
341 * ``reall_srchlen'' blocks in each list for a match (the variable
342 * is extern so the caller can modify it). If that fails we just copy
343 * however many bytes was given to realloc() and hope it's not huge.
345 int reall_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
352 register MEM_SIZE onb;
357 char *cp = (char*)mp;
361 MEM_SIZE size = nbytes;
365 if (nbytes > 0xffff) {
366 fprintf(stderr, "Reallocation too large: %lx\n", size);
371 return malloc(nbytes);
373 if ((long)nbytes < 0)
374 fatal("panic: realloc");
376 #endif /* safemalloc */
378 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
379 if (op->ov_magic == MAGIC) {
384 * Already free, doing "compaction".
386 * Search for the old block of memory on the
387 * free list. First, check the most common
388 * case (last element free'd), then (this failing)
389 * the last ``reall_srchlen'' items free'd.
390 * If all lookups fail, then assume the size of
391 * the memory block being realloc'd is the
394 if ((i = findbucket(op, 1)) < 0 &&
395 (i = findbucket(op, reall_srchlen)) < 0)
398 onb = (1L << (i + 3)) - sizeof (*op) - RSLOP;
399 /* avoid the copy if same size block */
401 nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP) {
404 * Record new allocated size of block and
405 * bound space with magic numbers.
407 if (op->ov_index <= 13) {
409 * Convert amount of memory requested into
410 * closest block size stored in hash buckets
411 * which satisfies request. Account for
412 * space used per block for accounting.
414 nbytes += sizeof (union overhead) + RSLOP;
415 nbytes = (nbytes + 3) &~ 3;
416 op->ov_size = nbytes - 1;
417 *((u_int *)((caddr_t)op + nbytes - RSLOP)) = RMAGIC;
423 if ((res = (char*)malloc(nbytes)) == NULL)
425 if (cp != res) /* common optimization */
426 Copy(cp, res, (MEM_SIZE)(nbytes<onb?nbytes:onb), char);
433 # if !(defined(I286) || defined(atarist))
435 fprintf(stderr,"0x%x: (%05d) rfree\n",res,an++);
436 fprintf(stderr,"0x%x: (%05d) realloc %ld bytes\n",res,an++,(long)size);
440 fprintf(stderr,"0x%lx: (%05d) rfree\n",res,an++);
441 fprintf(stderr,"0x%lx: (%05d) realloc %ld bytes\n",res,an++,(long)size);
445 #endif /* safemalloc */
446 return ((MALLOCPTRTYPE*)res);
450 * Search ``srchlen'' elements of each free list for a block whose
451 * header starts at ``freep''. If srchlen is -1 search the whole list.
452 * Return bucket number, or -1 if not found.
455 findbucket(freep, srchlen)
456 union overhead *freep;
459 register union overhead *p;
462 for (i = 0; i < NBUCKETS; i++) {
464 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
475 * mstats - print out statistics about malloc
477 * Prints two lines of numbers, one showing the length of the free list
478 * for each size category, the second showing the number of mallocs -
479 * frees for each size category.
486 register union overhead *p;
490 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
491 for (i = 0; i < NBUCKETS; i++) {
492 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
494 fprintf(stderr, " %d", j);
495 totfree += j * (1 << (i + 3));
497 fprintf(stderr, "\nused:\t");
498 for (i = 0; i < NBUCKETS; i++) {
499 fprintf(stderr, " %d", nmalloc[i]);
500 totused += nmalloc[i] * (1 << (i + 3));
502 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",