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);
180 #if !(defined(I286) || defined(atarist))
181 DEBUG_m(fprintf(stderr,"0x%x: (%05d) malloc %ld bytes\n",p+1,an++,(long)size));
183 DEBUG_m(fprintf(stderr,"0x%lx: (%05d) malloc %ld bytes\n",p+1,an++,(long)size));
185 #endif /* safemalloc */
187 /* remove from linked list */
189 if (*((int*)p) & (sizeof(union overhead) - 1))
190 #if !(defined(I286) || defined(atarist))
191 fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",*((int*)p),p);
193 fprintf(stderr,"Corrupt malloc ptr 0x%lx at 0x%lx\n",*((int*)p),p);
196 nextf[bucket] = p->ov_next;
204 * Record allocated size of block and
205 * bound space with magic numbers.
207 if (nbytes <= 0x10000)
208 p->ov_size = nbytes - 1;
209 p->ov_rmagic = RMAGIC;
210 *((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
212 return ((MALLOCPTRTYPE *)(p + 1));
216 * Allocate more memory to the indicated bucket.
222 register union overhead *op;
223 register int rnu; /* 2^rnu bytes will be requested */
224 register int nblks; /* become nblks blocks of the desired size */
225 register MEM_SIZE siz;
230 * Insure memory is allocated
231 * on a page boundary. Should
232 * make getpageize call?
234 #ifndef atarist /* on the atari we dont have to worry about this */
235 op = (union overhead *)sbrk(0);
238 (void)sbrk(1024 - ((int)op & 0x3ff));
240 /* The sbrk(0) call on the I286 always returns the next segment */
244 #if !(defined(I286) || defined(atarist))
245 /* take 2k unless the block is bigger than that */
246 rnu = (bucket <= 8) ? 11 : bucket + 3;
248 /* take 16k unless the block is bigger than that
249 (80286s like large segments!), probably good on the atari too */
250 rnu = (bucket <= 11) ? 14 : bucket + 3;
252 nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */
255 op = (union overhead *)sbrk(1L << rnu);
260 * Round up to minimum allocation size boundary
261 * and deduct from block count to reflect.
265 op = (union overhead *)(((MEM_SIZE)op + 8) &~ 7);
269 /* Again, this should always be ok on an 80286 */
272 * Add new memory allocated to that on
273 * free list for this hash bucket.
276 siz = 1 << (bucket + 3);
277 while (--nblks > 0) {
278 op->ov_next = (union overhead *)((caddr_t)op + siz);
279 op = (union overhead *)((caddr_t)op + siz);
287 register MEM_SIZE size;
288 register union overhead *op;
289 char *cp = (char*)mp;
292 #if !(defined(I286) || defined(atarist))
293 DEBUG_m(fprintf(stderr,"0x%x: (%05d) free\n",cp,an++));
295 DEBUG_m(fprintf(stderr,"0x%lx: (%05d) free\n",cp,an++));
297 #endif /* safemalloc */
301 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
303 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
305 if (op->ov_magic != MAGIC) {
306 warn("%s free() ignored",
307 op->ov_magic == OLDMAGIC ? "Duplicate" : "Bad");
310 op->ov_magic = OLDMAGIC;
313 ASSERT(op->ov_rmagic == RMAGIC);
314 if (op->ov_index <= 13)
315 ASSERT(*(u_int *)((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC);
317 ASSERT(op->ov_index < NBUCKETS);
319 op->ov_next = nextf[size];
327 * When a program attempts "storage compaction" as mentioned in the
328 * old malloc man page, it realloc's an already freed block. Usually
329 * this is the last block it freed; occasionally it might be farther
330 * back. We have to search all the free lists for the block in order
331 * to determine its bucket: 1st we make one pass thru the lists
332 * checking only the first block in each; if that fails we search
333 * ``reall_srchlen'' blocks in each list for a match (the variable
334 * is extern so the caller can modify it). If that fails we just copy
335 * however many bytes was given to realloc() and hope it's not huge.
337 int reall_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
344 register MEM_SIZE onb;
349 char *cp = (char*)mp;
353 MEM_SIZE size = nbytes;
357 if (nbytes > 0xffff) {
358 fprintf(stderr, "Reallocation too large: %lx\n", size);
363 return malloc(nbytes);
365 if ((long)nbytes < 0)
366 fatal("panic: realloc");
368 #endif /* safemalloc */
370 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
371 if (op->ov_magic == MAGIC) {
376 * Already free, doing "compaction".
378 * Search for the old block of memory on the
379 * free list. First, check the most common
380 * case (last element free'd), then (this failing)
381 * the last ``reall_srchlen'' items free'd.
382 * If all lookups fail, then assume the size of
383 * the memory block being realloc'd is the
386 if ((i = findbucket(op, 1)) < 0 &&
387 (i = findbucket(op, reall_srchlen)) < 0)
390 onb = (1L << (i + 3)) - sizeof (*op) - RSLOP;
391 /* avoid the copy if same size block */
393 nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP) {
396 * Record new allocated size of block and
397 * bound space with magic numbers.
399 if (op->ov_index <= 13) {
401 * Convert amount of memory requested into
402 * closest block size stored in hash buckets
403 * which satisfies request. Account for
404 * space used per block for accounting.
406 nbytes += sizeof (union overhead) + RSLOP;
407 nbytes = (nbytes + 3) &~ 3;
408 op->ov_size = nbytes - 1;
409 *((u_int *)((caddr_t)op + nbytes - RSLOP)) = RMAGIC;
415 if ((res = (char*)malloc(nbytes)) == NULL)
417 if (cp != res) /* common optimization */
418 Copy(cp, res, (MEM_SIZE)(nbytes<onb?nbytes:onb), char);
425 # if !(defined(I286) || defined(atarist))
427 fprintf(stderr,"0x%x: (%05d) rfree\n",res,an++);
428 fprintf(stderr,"0x%x: (%05d) realloc %ld bytes\n",res,an++,(long)size);
432 fprintf(stderr,"0x%lx: (%05d) rfree\n",res,an++);
433 fprintf(stderr,"0x%lx: (%05d) realloc %ld bytes\n",res,an++,(long)size);
437 #endif /* safemalloc */
438 return ((MALLOCPTRTYPE*)res);
442 * Search ``srchlen'' elements of each free list for a block whose
443 * header starts at ``freep''. If srchlen is -1 search the whole list.
444 * Return bucket number, or -1 if not found.
447 findbucket(freep, srchlen)
448 union overhead *freep;
451 register union overhead *p;
454 for (i = 0; i < NBUCKETS; i++) {
456 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
467 * mstats - print out statistics about malloc
469 * Prints two lines of numbers, one showing the length of the free list
470 * for each size category, the second showing the number of mallocs -
471 * frees for each size category.
478 register union overhead *p;
482 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
483 for (i = 0; i < NBUCKETS; i++) {
484 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
486 fprintf(stderr, " %d", j);
487 totfree += j * (1 << (i + 3));
489 fprintf(stderr, "\nused:\t");
490 for (i = 0; i < NBUCKETS; i++) {
491 fprintf(stderr, " %d", nmalloc[i]);
492 totused += nmalloc[i] * (1 << (i + 3));
494 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",