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 */
67 #if MEM_ALIGNBYTES > 4
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 RMAGIC 0x55555555 /* magic # on range info */
87 #define RSLOP sizeof (u_int)
93 * nextf[i] is the pointer to the next free block of size 2^(i+3). The
94 * smallest allocatable block is 8 bytes. The overhead information
95 * precedes the data area returned to the user.
98 static union overhead *nextf[NBUCKETS];
103 * nmalloc[i] is the difference between the number of mallocs and frees
104 * for a given block size.
106 static u_int nmalloc[NBUCKETS];
111 #define ASSERT(p) if (!(p)) botch("p"); else
117 printf("assertion botched: %s\n", s);
126 register MEM_SIZE nbytes;
128 register union overhead *p;
129 register int bucket = 0;
130 register MEM_SIZE shiftr;
134 MEM_SIZE size = nbytes;
138 if (nbytes > 0xffff) {
139 fprintf(stderr, "Allocation too large: %lx\n", (long)nbytes);
144 if ((long)nbytes < 0)
145 croak("panic: malloc");
147 #endif /* safemalloc */
150 * Convert amount of memory requested into
151 * closest block size stored in hash buckets
152 * which satisfies request. Account for
153 * space used per block for accounting.
155 nbytes += sizeof (union overhead) + RSLOP;
156 nbytes = (nbytes + 3) &~ 3;
157 shiftr = (nbytes - 1) >> 2;
158 /* apart from this loop, this is O(1) */
162 * If nothing in hash bucket right now,
163 * request more memory from the system.
165 if (nextf[bucket] == NULL)
167 if ((p = (union overhead *)nextf[bucket]) == NULL) {
170 fputs("Out of memory!\n", stderr);
179 #if !(defined(I286) || defined(atarist))
180 DEBUG_m(fprintf(stderr,"0x%x: (%05d) malloc %ld bytes\n",p+1,an++,(long)size));
182 DEBUG_m(fprintf(stderr,"0x%lx: (%05d) malloc %ld bytes\n",p+1,an++,(long)size));
184 #endif /* safemalloc */
186 /* remove from linked list */
188 if (*((int*)p) & (sizeof(union overhead) - 1))
189 #if !(defined(I286) || defined(atarist))
190 fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",*((int*)p),p);
192 fprintf(stderr,"Corrupt malloc ptr 0x%lx at 0x%lx\n",*((int*)p),p);
195 nextf[bucket] = p->ov_next;
203 * Record allocated size of block and
204 * bound space with magic numbers.
206 if (nbytes <= 0x10000)
207 p->ov_size = nbytes - 1;
208 p->ov_rmagic = RMAGIC;
209 *((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
211 return ((Malloc_t)(p + 1));
215 * Allocate more memory to the indicated bucket.
221 register union overhead *op;
222 register int rnu; /* 2^rnu bytes will be requested */
223 register int nblks; /* become nblks blocks of the desired size */
224 register MEM_SIZE siz;
229 * Insure memory is allocated
230 * on a page boundary. Should
231 * make getpageize call?
233 #ifndef atarist /* on the atari we dont have to worry about this */
234 op = (union overhead *)sbrk(0);
237 (void)sbrk(1024 - ((int)op & 0x3ff));
239 /* The sbrk(0) call on the I286 always returns the next segment */
243 #if !(defined(I286) || defined(atarist))
244 /* take 2k unless the block is bigger than that */
245 rnu = (bucket <= 8) ? 11 : bucket + 3;
247 /* take 16k unless the block is bigger than that
248 (80286s like large segments!), probably good on the atari too */
249 rnu = (bucket <= 11) ? 14 : bucket + 3;
251 nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */
254 op = (union overhead *)sbrk(1L << rnu);
259 * Round up to minimum allocation size boundary
260 * and deduct from block count to reflect.
264 op = (union overhead *)(((MEM_SIZE)op + 8) &~ 7);
268 /* Again, this should always be ok on an 80286 */
271 * Add new memory allocated to that on
272 * free list for this hash bucket.
275 siz = 1 << (bucket + 3);
276 while (--nblks > 0) {
277 op->ov_next = (union overhead *)((caddr_t)op + siz);
278 op = (union overhead *)((caddr_t)op + siz);
286 register MEM_SIZE size;
287 register union overhead *op;
288 char *cp = (char*)mp;
291 #if !(defined(I286) || defined(atarist))
292 DEBUG_m(fprintf(stderr,"0x%x: (%05d) free\n",cp,an++));
294 DEBUG_m(fprintf(stderr,"0x%lx: (%05d) free\n",cp,an++));
296 #endif /* safemalloc */
300 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
302 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
304 if (op->ov_magic != MAGIC) {
306 warn("%s free() ignored",
307 op->ov_rmagic == RMAGIC - 1 ? "Duplicate" : "Bad");
309 warn("Bad free() ignored");
315 ASSERT(op->ov_rmagic == RMAGIC);
316 if (op->ov_index <= 13)
317 ASSERT(*(u_int *)((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC);
318 op->ov_rmagic = RMAGIC - 1;
320 ASSERT(op->ov_index < NBUCKETS);
322 op->ov_next = nextf[size];
330 * When a program attempts "storage compaction" as mentioned in the
331 * old malloc man page, it realloc's an already freed block. Usually
332 * this is the last block it freed; occasionally it might be farther
333 * back. We have to search all the free lists for the block in order
334 * to determine its bucket: 1st we make one pass thru the lists
335 * checking only the first block in each; if that fails we search
336 * ``reall_srchlen'' blocks in each list for a match (the variable
337 * is extern so the caller can modify it). If that fails we just copy
338 * however many bytes was given to realloc() and hope it's not huge.
340 int reall_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
347 register MEM_SIZE onb;
352 char *cp = (char*)mp;
356 MEM_SIZE size = nbytes;
360 if (nbytes > 0xffff) {
361 fprintf(stderr, "Reallocation too large: %lx\n", size);
366 return malloc(nbytes);
368 if ((long)nbytes < 0)
369 croak("panic: realloc");
371 #endif /* safemalloc */
373 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
374 if (op->ov_magic == MAGIC) {
379 * Already free, doing "compaction".
381 * Search for the old block of memory on the
382 * free list. First, check the most common
383 * case (last element free'd), then (this failing)
384 * the last ``reall_srchlen'' items free'd.
385 * If all lookups fail, then assume the size of
386 * the memory block being realloc'd is the
389 if ((i = findbucket(op, 1)) < 0 &&
390 (i = findbucket(op, reall_srchlen)) < 0)
393 onb = (1L << (i + 3)) - sizeof (*op) - RSLOP;
394 /* avoid the copy if same size block */
396 nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP) {
399 * Record new allocated size of block and
400 * bound space with magic numbers.
402 if (op->ov_index <= 13) {
404 * Convert amount of memory requested into
405 * closest block size stored in hash buckets
406 * which satisfies request. Account for
407 * space used per block for accounting.
409 nbytes += sizeof (union overhead) + RSLOP;
410 nbytes = (nbytes + 3) &~ 3;
411 op->ov_size = nbytes - 1;
412 *((u_int *)((caddr_t)op + nbytes - RSLOP)) = RMAGIC;
418 if ((res = (char*)malloc(nbytes)) == NULL)
420 if (cp != res) /* common optimization */
421 Copy(cp, res, (MEM_SIZE)(nbytes<onb?nbytes:onb), char);
428 # if !(defined(I286) || defined(atarist))
430 fprintf(stderr,"0x%x: (%05d) rfree\n",res,an++);
431 fprintf(stderr,"0x%x: (%05d) realloc %ld bytes\n",res,an++,(long)size);
435 fprintf(stderr,"0x%lx: (%05d) rfree\n",res,an++);
436 fprintf(stderr,"0x%lx: (%05d) realloc %ld bytes\n",res,an++,(long)size);
440 #endif /* safemalloc */
441 return ((Malloc_t)res);
445 * Search ``srchlen'' elements of each free list for a block whose
446 * header starts at ``freep''. If srchlen is -1 search the whole list.
447 * Return bucket number, or -1 if not found.
450 findbucket(freep, srchlen)
451 union overhead *freep;
454 register union overhead *p;
457 for (i = 0; i < NBUCKETS; i++) {
459 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
470 * mstats - print out statistics about malloc
472 * Prints two lines of numbers, one showing the length of the free list
473 * for each size category, the second showing the number of mallocs -
474 * frees for each size category.
481 register union overhead *p;
485 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
486 for (i = 0; i < NBUCKETS; i++) {
487 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
489 fprintf(stderr, " %d", j);
490 totfree += j * (1 << (i + 3));
492 fprintf(stderr, "\nused:\t");
493 for (i = 0; i < NBUCKETS; i++) {
494 fprintf(stderr, " %d", nmalloc[i]);
495 totused += nmalloc[i] * (1 << (i + 3));
497 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",