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79072805 1/* $RCSfile: malloc.c,v $$Revision: 4.1 $$Date: 92/08/07 18:24:25 $
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2 *
3 * $Log: malloc.c,v $
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4 * Revision 4.1 92/08/07 18:24:25 lwall
5 *
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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
10 *
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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
13 *
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14 * Revision 4.0.1.2 91/06/07 11:20:45 lwall
15 * patch4: many, many itty-bitty portability fixes
16 *
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17 * Revision 4.0.1.1 91/04/11 17:48:31 lwall
18 * patch1: Configure now figures out malloc ptr type
19 *
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20 * Revision 4.0 91/03/20 01:28:52 lwall
21 * 4.0 baseline.
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22 *
23 */
24
25#ifndef lint
45d8adaa 26/*SUPPRESS 592*/
8d063cd8 27static char sccsid[] = "@(#)malloc.c 4.3 (Berkeley) 9/16/83";
8d063cd8 28
a687059c 29#ifdef DEBUGGING
8d063cd8 30#define RCHECK
a687059c 31#endif
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32/*
33 * malloc.c (Caltech) 2/21/82
34 * Chris Kingsley, kingsley@cit-20.
35 *
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.
42 */
43
135863df 44#include "EXTERN.h"
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45#include "perl.h"
46
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47static int findbucket();
48static int morecore();
03a14243 49
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50/* I don't much care whether these are defined in sys/types.h--LAW */
51
52#define u_char unsigned char
53#define u_int unsigned int
54#define u_short unsigned short
8d063cd8 55
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56/*
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.
64 */
65union overhead {
66 union overhead *ov_next; /* when free */
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67#if ALIGNBYTES > 4
68 double strut; /* alignment problems */
a687059c 69#endif
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70 struct {
71 u_char ovu_magic; /* magic number */
72 u_char ovu_index; /* bucket # */
73#ifdef RCHECK
74 u_short ovu_size; /* actual block size */
75 u_int ovu_rmagic; /* range magic number */
76#endif
77 } ovu;
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
82};
83
84#define MAGIC 0xff /* magic # on accounting info */
378cc40b 85#define OLDMAGIC 0x7f /* same after a free() */
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86#define RMAGIC 0x55555555 /* magic # on range info */
87#ifdef RCHECK
88#define RSLOP sizeof (u_int)
89#else
90#define RSLOP 0
91#endif
92
93/*
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.
97 */
98#define NBUCKETS 30
99static union overhead *nextf[NBUCKETS];
100extern char *sbrk();
101
102#ifdef MSTATS
103/*
104 * nmalloc[i] is the difference between the number of mallocs and frees
105 * for a given block size.
106 */
107static u_int nmalloc[NBUCKETS];
108#include <stdio.h>
109#endif
110
111#ifdef debug
112#define ASSERT(p) if (!(p)) botch("p"); else
ee0007ab 113static void
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114botch(s)
115 char *s;
116{
117
118 printf("assertion botched: %s\n", s);
119 abort();
120}
121#else
122#define ASSERT(p)
123#endif
124
35c8bce7 125MALLOCPTRTYPE *
8d063cd8 126malloc(nbytes)
ee0007ab 127 register MEM_SIZE nbytes;
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128{
129 register union overhead *p;
130 register int bucket = 0;
ee0007ab 131 register MEM_SIZE shiftr;
8d063cd8 132
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133#ifdef safemalloc
134#ifdef DEBUGGING
ee0007ab 135 MEM_SIZE size = nbytes;
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136#endif
137
138#ifdef MSDOS
139 if (nbytes > 0xffff) {
ee0007ab 140 fprintf(stderr, "Allocation too large: %lx\n", (long)nbytes);
79072805 141 my_exit(1);
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142 }
143#endif /* MSDOS */
144#ifdef DEBUGGING
145 if ((long)nbytes < 0)
463ee0b2 146 croak("panic: malloc");
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147#endif
148#endif /* safemalloc */
149
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150 /*
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.
155 */
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) */
160 while (shiftr >>= 1)
161 bucket++;
162 /*
163 * If nothing in hash bucket right now,
164 * request more memory from the system.
165 */
166 if (nextf[bucket] == NULL)
167 morecore(bucket);
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168 if ((p = (union overhead *)nextf[bucket]) == NULL) {
169#ifdef safemalloc
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170 if (!nomemok) {
171 fputs("Out of memory!\n", stderr);
79072805 172 my_exit(1);
ee0007ab 173 }
45d8adaa 174#else
8d063cd8 175 return (NULL);
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176#endif
177 }
178
179#ifdef safemalloc
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180#if !(defined(I286) || defined(atarist))
181 DEBUG_m(fprintf(stderr,"0x%x: (%05d) malloc %ld bytes\n",p+1,an++,(long)size));
182#else
183 DEBUG_m(fprintf(stderr,"0x%lx: (%05d) malloc %ld bytes\n",p+1,an++,(long)size));
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184#endif
185#endif /* safemalloc */
186
8d063cd8 187 /* remove from linked list */
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188#ifdef RCHECK
189 if (*((int*)p) & (sizeof(union overhead) - 1))
ee0007ab 190#if !(defined(I286) || defined(atarist))
8d063cd8 191 fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",*((int*)p),p);
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192#else
193 fprintf(stderr,"Corrupt malloc ptr 0x%lx at 0x%lx\n",*((int*)p),p);
194#endif
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195#endif
196 nextf[bucket] = p->ov_next;
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197 p->ov_magic = MAGIC;
198 p->ov_index= bucket;
199#ifdef MSTATS
200 nmalloc[bucket]++;
201#endif
202#ifdef RCHECK
203 /*
204 * Record allocated size of block and
205 * bound space with magic numbers.
206 */
207 if (nbytes <= 0x10000)
208 p->ov_size = nbytes - 1;
209 p->ov_rmagic = RMAGIC;
210 *((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
211#endif
352d5a3a 212 return ((MALLOCPTRTYPE *)(p + 1));
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213}
214
215/*
216 * Allocate more memory to the indicated bucket.
217 */
218static
219morecore(bucket)
a687059c 220 register int bucket;
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221{
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 */
ee0007ab 225 register MEM_SIZE siz;
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226
227 if (nextf[bucket])
228 return;
229 /*
230 * Insure memory is allocated
231 * on a page boundary. Should
232 * make getpageize call?
233 */
ee0007ab 234#ifndef atarist /* on the atari we dont have to worry about this */
8d063cd8 235 op = (union overhead *)sbrk(0);
a687059c 236#ifndef I286
8d063cd8 237 if ((int)op & 0x3ff)
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238 (void)sbrk(1024 - ((int)op & 0x3ff));
239#else
240 /* The sbrk(0) call on the I286 always returns the next segment */
241#endif
ee0007ab 242#endif /* atarist */
a687059c 243
ee0007ab 244#if !(defined(I286) || defined(atarist))
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245 /* take 2k unless the block is bigger than that */
246 rnu = (bucket <= 8) ? 11 : bucket + 3;
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247#else
248 /* take 16k unless the block is bigger than that
ee0007ab 249 (80286s like large segments!), probably good on the atari too */
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250 rnu = (bucket <= 11) ? 14 : bucket + 3;
251#endif
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252 nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */
253 if (rnu < bucket)
254 rnu = bucket;
ee0007ab 255 op = (union overhead *)sbrk(1L << rnu);
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256 /* no more room! */
257 if ((int)op == -1)
258 return;
259 /*
260 * Round up to minimum allocation size boundary
261 * and deduct from block count to reflect.
262 */
a687059c 263#ifndef I286
8d063cd8 264 if ((int)op & 7) {
ee0007ab 265 op = (union overhead *)(((MEM_SIZE)op + 8) &~ 7);
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266 nblks--;
267 }
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268#else
269 /* Again, this should always be ok on an 80286 */
270#endif
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271 /*
272 * Add new memory allocated to that on
273 * free list for this hash bucket.
274 */
275 nextf[bucket] = op;
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);
280 }
281}
282
fe14fcc3 283void
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284free(mp)
285 MALLOCPTRTYPE *mp;
8d063cd8 286{
ee0007ab 287 register MEM_SIZE size;
8d063cd8 288 register union overhead *op;
352d5a3a 289 char *cp = (char*)mp;
8d063cd8 290
45d8adaa 291#ifdef safemalloc
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292#if !(defined(I286) || defined(atarist))
293 DEBUG_m(fprintf(stderr,"0x%x: (%05d) free\n",cp,an++));
294#else
295 DEBUG_m(fprintf(stderr,"0x%lx: (%05d) free\n",cp,an++));
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296#endif
297#endif /* safemalloc */
298
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299 if (cp == NULL)
300 return;
301 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
302#ifdef debug
303 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
304#else
378cc40b 305 if (op->ov_magic != MAGIC) {
a687059c 306 warn("%s free() ignored",
378cc40b 307 op->ov_magic == OLDMAGIC ? "Duplicate" : "Bad");
8d063cd8 308 return; /* sanity */
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309 }
310 op->ov_magic = OLDMAGIC;
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311#endif
312#ifdef RCHECK
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);
316#endif
317 ASSERT(op->ov_index < NBUCKETS);
318 size = op->ov_index;
319 op->ov_next = nextf[size];
320 nextf[size] = op;
321#ifdef MSTATS
322 nmalloc[size]--;
323#endif
324}
325
326/*
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
378cc40b 333 * ``reall_srchlen'' blocks in each list for a match (the variable
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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.
336 */
378cc40b 337int reall_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
8d063cd8 338
35c8bce7 339MALLOCPTRTYPE *
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340realloc(mp, nbytes)
341 MALLOCPTRTYPE *mp;
ee0007ab 342 MEM_SIZE nbytes;
8d063cd8 343{
ee0007ab 344 register MEM_SIZE onb;
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345 union overhead *op;
346 char *res;
347 register int i;
348 int was_alloced = 0;
352d5a3a 349 char *cp = (char*)mp;
8d063cd8 350
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351#ifdef safemalloc
352#ifdef DEBUGGING
ee0007ab 353 MEM_SIZE size = nbytes;
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354#endif
355
356#ifdef MSDOS
357 if (nbytes > 0xffff) {
358 fprintf(stderr, "Reallocation too large: %lx\n", size);
79072805 359 my_exit(1);
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360 }
361#endif /* MSDOS */
362 if (!cp)
ee0007ab 363 return malloc(nbytes);
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364#ifdef DEBUGGING
365 if ((long)nbytes < 0)
463ee0b2 366 croak("panic: realloc");
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367#endif
368#endif /* safemalloc */
369
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370 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
371 if (op->ov_magic == MAGIC) {
372 was_alloced++;
373 i = op->ov_index;
374 } else {
375 /*
376 * Already free, doing "compaction".
377 *
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)
378cc40b 381 * the last ``reall_srchlen'' items free'd.
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382 * If all lookups fail, then assume the size of
383 * the memory block being realloc'd is the
384 * smallest possible.
385 */
386 if ((i = findbucket(op, 1)) < 0 &&
378cc40b 387 (i = findbucket(op, reall_srchlen)) < 0)
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388 i = 0;
389 }
ee0007ab 390 onb = (1L << (i + 3)) - sizeof (*op) - RSLOP;
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391 /* avoid the copy if same size block */
392 if (was_alloced &&
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393 nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP) {
394#ifdef RCHECK
395 /*
396 * Record new allocated size of block and
397 * bound space with magic numbers.
398 */
399 if (op->ov_index <= 13) {
400 /*
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.
405 */
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;
410 }
411#endif
45d8adaa 412 res = cp;
a687059c 413 }
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414 else {
415 if ((res = (char*)malloc(nbytes)) == NULL)
416 return (NULL);
417 if (cp != res) /* common optimization */
ee0007ab 418 Copy(cp, res, (MEM_SIZE)(nbytes<onb?nbytes:onb), char);
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419 if (was_alloced)
420 free(cp);
421 }
422
423#ifdef safemalloc
424#ifdef DEBUGGING
ee0007ab 425# if !(defined(I286) || defined(atarist))
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426 if (debug & 128) {
427 fprintf(stderr,"0x%x: (%05d) rfree\n",res,an++);
ee0007ab 428 fprintf(stderr,"0x%x: (%05d) realloc %ld bytes\n",res,an++,(long)size);
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429 }
430# else
431 if (debug & 128) {
432 fprintf(stderr,"0x%lx: (%05d) rfree\n",res,an++);
ee0007ab 433 fprintf(stderr,"0x%lx: (%05d) realloc %ld bytes\n",res,an++,(long)size);
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434 }
435# endif
436#endif
437#endif /* safemalloc */
352d5a3a 438 return ((MALLOCPTRTYPE*)res);
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439}
440
441/*
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.
445 */
ee0007ab 446static int
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447findbucket(freep, srchlen)
448 union overhead *freep;
449 int srchlen;
450{
451 register union overhead *p;
452 register int i, j;
453
454 for (i = 0; i < NBUCKETS; i++) {
455 j = 0;
456 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
457 if (p == freep)
458 return (i);
459 j++;
460 }
461 }
462 return (-1);
463}
464
465#ifdef MSTATS
466/*
467 * mstats - print out statistics about malloc
468 *
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.
472 */
ee0007ab 473void
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474mstats(s)
475 char *s;
476{
477 register int i, j;
478 register union overhead *p;
479 int totfree = 0,
480 totused = 0;
481
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++)
485 ;
486 fprintf(stderr, " %d", j);
487 totfree += j * (1 << (i + 3));
488 }
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));
493 }
494 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
495 totused, totfree);
496}
497#endif
a687059c 498#endif /* lint */