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perl 3.0 patch #41 (combined patch)
[perl5.git] / malloc.c
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4e8eb4f0 1/* $Header: malloc.c,v 3.0.1.4 90/11/13 15:23:45 lwall Locked $
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2 *
3 * $Log: malloc.c,v $
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4 * Revision 3.0.1.4 90/11/13 15:23:45 lwall
5 * patch41: added hp malloc union overhead strut (that sounds very blue collar)
6 *
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7 * Revision 3.0.1.3 90/10/16 15:27:47 lwall
8 * patch29: various portability fixes
9 *
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10 * Revision 3.0.1.2 89/11/11 04:36:37 lwall
11 * patch2: malloc pointer corruption check made more portable
12 *
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13 * Revision 3.0.1.1 89/10/26 23:15:05 lwall
14 * patch1: some declarations were missing from malloc.c
15 * patch1: sparc machines had alignment problems in malloc.c
16 *
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17 * Revision 3.0 89/10/18 15:20:39 lwall
18 * 3.0 baseline
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19 *
20 */
21
22#ifndef lint
23static char sccsid[] = "@(#)malloc.c 4.3 (Berkeley) 9/16/83";
8d063cd8 24
a687059c 25#ifdef DEBUGGING
8d063cd8 26#define RCHECK
a687059c 27#endif
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28/*
29 * malloc.c (Caltech) 2/21/82
30 * Chris Kingsley, kingsley@cit-20.
31 *
32 * This is a very fast storage allocator. It allocates blocks of a small
33 * number of different sizes, and keeps free lists of each size. Blocks that
34 * don't exactly fit are passed up to the next larger size. In this
35 * implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long.
36 * This is designed for use in a program that uses vast quantities of memory,
37 * but bombs when it runs out.
38 */
39
135863df 40#include "EXTERN.h"
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41#include "perl.h"
42
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43static findbucket(), morecore();
44
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45/* I don't much care whether these are defined in sys/types.h--LAW */
46
47#define u_char unsigned char
48#define u_int unsigned int
49#define u_short unsigned short
8d063cd8 50
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51/*
52 * The overhead on a block is at least 4 bytes. When free, this space
53 * contains a pointer to the next free block, and the bottom two bits must
54 * be zero. When in use, the first byte is set to MAGIC, and the second
55 * byte is the size index. The remaining bytes are for alignment.
56 * If range checking is enabled and the size of the block fits
57 * in two bytes, then the top two bytes hold the size of the requested block
58 * plus the range checking words, and the header word MINUS ONE.
59 */
60union overhead {
61 union overhead *ov_next; /* when free */
4e8eb4f0 62#if defined(mips) || defined(sparc) || defined(luna88k) || defined(hp9000s800)
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63 double strut; /* alignment problems */
64#endif
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65 struct {
66 u_char ovu_magic; /* magic number */
67 u_char ovu_index; /* bucket # */
68#ifdef RCHECK
69 u_short ovu_size; /* actual block size */
70 u_int ovu_rmagic; /* range magic number */
71#endif
72 } ovu;
73#define ov_magic ovu.ovu_magic
74#define ov_index ovu.ovu_index
75#define ov_size ovu.ovu_size
76#define ov_rmagic ovu.ovu_rmagic
77};
78
79#define MAGIC 0xff /* magic # on accounting info */
378cc40b 80#define OLDMAGIC 0x7f /* same after a free() */
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81#define RMAGIC 0x55555555 /* magic # on range info */
82#ifdef RCHECK
83#define RSLOP sizeof (u_int)
84#else
85#define RSLOP 0
86#endif
87
88/*
89 * nextf[i] is the pointer to the next free block of size 2^(i+3). The
90 * smallest allocatable block is 8 bytes. The overhead information
91 * precedes the data area returned to the user.
92 */
93#define NBUCKETS 30
94static union overhead *nextf[NBUCKETS];
95extern char *sbrk();
96
97#ifdef MSTATS
98/*
99 * nmalloc[i] is the difference between the number of mallocs and frees
100 * for a given block size.
101 */
102static u_int nmalloc[NBUCKETS];
103#include <stdio.h>
104#endif
105
106#ifdef debug
107#define ASSERT(p) if (!(p)) botch("p"); else
108static
109botch(s)
110 char *s;
111{
112
113 printf("assertion botched: %s\n", s);
114 abort();
115}
116#else
117#define ASSERT(p)
118#endif
119
120char *
121malloc(nbytes)
122 register unsigned nbytes;
123{
124 register union overhead *p;
125 register int bucket = 0;
126 register unsigned shiftr;
127
128 /*
129 * Convert amount of memory requested into
130 * closest block size stored in hash buckets
131 * which satisfies request. Account for
132 * space used per block for accounting.
133 */
134 nbytes += sizeof (union overhead) + RSLOP;
135 nbytes = (nbytes + 3) &~ 3;
136 shiftr = (nbytes - 1) >> 2;
137 /* apart from this loop, this is O(1) */
138 while (shiftr >>= 1)
139 bucket++;
140 /*
141 * If nothing in hash bucket right now,
142 * request more memory from the system.
143 */
144 if (nextf[bucket] == NULL)
145 morecore(bucket);
146 if ((p = (union overhead *)nextf[bucket]) == NULL)
147 return (NULL);
148 /* remove from linked list */
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149#ifdef RCHECK
150 if (*((int*)p) & (sizeof(union overhead) - 1))
a687059c 151#ifndef I286
8d063cd8 152 fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",*((int*)p),p);
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153#else
154 fprintf(stderr,"Corrupt malloc ptr 0x%lx at 0x%lx\n",*((int*)p),p);
155#endif
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156#endif
157 nextf[bucket] = p->ov_next;
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158 p->ov_magic = MAGIC;
159 p->ov_index= bucket;
160#ifdef MSTATS
161 nmalloc[bucket]++;
162#endif
163#ifdef RCHECK
164 /*
165 * Record allocated size of block and
166 * bound space with magic numbers.
167 */
168 if (nbytes <= 0x10000)
169 p->ov_size = nbytes - 1;
170 p->ov_rmagic = RMAGIC;
171 *((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
172#endif
173 return ((char *)(p + 1));
174}
175
176/*
177 * Allocate more memory to the indicated bucket.
178 */
179static
180morecore(bucket)
a687059c 181 register int bucket;
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182{
183 register union overhead *op;
184 register int rnu; /* 2^rnu bytes will be requested */
185 register int nblks; /* become nblks blocks of the desired size */
186 register int siz;
187
188 if (nextf[bucket])
189 return;
190 /*
191 * Insure memory is allocated
192 * on a page boundary. Should
193 * make getpageize call?
194 */
195 op = (union overhead *)sbrk(0);
a687059c 196#ifndef I286
8d063cd8 197 if ((int)op & 0x3ff)
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198 (void)sbrk(1024 - ((int)op & 0x3ff));
199#else
200 /* The sbrk(0) call on the I286 always returns the next segment */
201#endif
202
203#ifndef I286
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204 /* take 2k unless the block is bigger than that */
205 rnu = (bucket <= 8) ? 11 : bucket + 3;
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206#else
207 /* take 16k unless the block is bigger than that
208 (80286s like large segments!) */
209 rnu = (bucket <= 11) ? 14 : bucket + 3;
210#endif
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211 nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */
212 if (rnu < bucket)
213 rnu = bucket;
214 op = (union overhead *)sbrk(1 << rnu);
215 /* no more room! */
216 if ((int)op == -1)
217 return;
218 /*
219 * Round up to minimum allocation size boundary
220 * and deduct from block count to reflect.
221 */
a687059c 222#ifndef I286
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223 if ((int)op & 7) {
224 op = (union overhead *)(((int)op + 8) &~ 7);
225 nblks--;
226 }
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227#else
228 /* Again, this should always be ok on an 80286 */
229#endif
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230 /*
231 * Add new memory allocated to that on
232 * free list for this hash bucket.
233 */
234 nextf[bucket] = op;
235 siz = 1 << (bucket + 3);
236 while (--nblks > 0) {
237 op->ov_next = (union overhead *)((caddr_t)op + siz);
238 op = (union overhead *)((caddr_t)op + siz);
239 }
240}
241
242free(cp)
243 char *cp;
244{
245 register int size;
246 register union overhead *op;
247
248 if (cp == NULL)
249 return;
250 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
251#ifdef debug
252 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
253#else
378cc40b 254 if (op->ov_magic != MAGIC) {
a687059c 255 warn("%s free() ignored",
378cc40b 256 op->ov_magic == OLDMAGIC ? "Duplicate" : "Bad");
8d063cd8 257 return; /* sanity */
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258 }
259 op->ov_magic = OLDMAGIC;
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260#endif
261#ifdef RCHECK
262 ASSERT(op->ov_rmagic == RMAGIC);
263 if (op->ov_index <= 13)
264 ASSERT(*(u_int *)((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC);
265#endif
266 ASSERT(op->ov_index < NBUCKETS);
267 size = op->ov_index;
268 op->ov_next = nextf[size];
269 nextf[size] = op;
270#ifdef MSTATS
271 nmalloc[size]--;
272#endif
273}
274
275/*
276 * When a program attempts "storage compaction" as mentioned in the
277 * old malloc man page, it realloc's an already freed block. Usually
278 * this is the last block it freed; occasionally it might be farther
279 * back. We have to search all the free lists for the block in order
280 * to determine its bucket: 1st we make one pass thru the lists
281 * checking only the first block in each; if that fails we search
378cc40b 282 * ``reall_srchlen'' blocks in each list for a match (the variable
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283 * is extern so the caller can modify it). If that fails we just copy
284 * however many bytes was given to realloc() and hope it's not huge.
285 */
378cc40b 286int reall_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
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287
288char *
289realloc(cp, nbytes)
290 char *cp;
291 unsigned nbytes;
292{
293 register u_int onb;
294 union overhead *op;
295 char *res;
296 register int i;
297 int was_alloced = 0;
298
299 if (cp == NULL)
300 return (malloc(nbytes));
301 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
302 if (op->ov_magic == MAGIC) {
303 was_alloced++;
304 i = op->ov_index;
305 } else {
306 /*
307 * Already free, doing "compaction".
308 *
309 * Search for the old block of memory on the
310 * free list. First, check the most common
311 * case (last element free'd), then (this failing)
378cc40b 312 * the last ``reall_srchlen'' items free'd.
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313 * If all lookups fail, then assume the size of
314 * the memory block being realloc'd is the
315 * smallest possible.
316 */
317 if ((i = findbucket(op, 1)) < 0 &&
378cc40b 318 (i = findbucket(op, reall_srchlen)) < 0)
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319 i = 0;
320 }
321 onb = (1 << (i + 3)) - sizeof (*op) - RSLOP;
322 /* avoid the copy if same size block */
323 if (was_alloced &&
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324 nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP) {
325#ifdef RCHECK
326 /*
327 * Record new allocated size of block and
328 * bound space with magic numbers.
329 */
330 if (op->ov_index <= 13) {
331 /*
332 * Convert amount of memory requested into
333 * closest block size stored in hash buckets
334 * which satisfies request. Account for
335 * space used per block for accounting.
336 */
337 nbytes += sizeof (union overhead) + RSLOP;
338 nbytes = (nbytes + 3) &~ 3;
339 op->ov_size = nbytes - 1;
340 *((u_int *)((caddr_t)op + nbytes - RSLOP)) = RMAGIC;
341 }
342#endif
8d063cd8 343 return(cp);
a687059c 344 }
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345 if ((res = malloc(nbytes)) == NULL)
346 return (NULL);
347 if (cp != res) /* common optimization */
a687059c 348 (void)bcopy(cp, res, (int)((nbytes < onb) ? nbytes : onb));
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349 if (was_alloced)
350 free(cp);
351 return (res);
352}
353
354/*
355 * Search ``srchlen'' elements of each free list for a block whose
356 * header starts at ``freep''. If srchlen is -1 search the whole list.
357 * Return bucket number, or -1 if not found.
358 */
359static
360findbucket(freep, srchlen)
361 union overhead *freep;
362 int srchlen;
363{
364 register union overhead *p;
365 register int i, j;
366
367 for (i = 0; i < NBUCKETS; i++) {
368 j = 0;
369 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
370 if (p == freep)
371 return (i);
372 j++;
373 }
374 }
375 return (-1);
376}
377
378#ifdef MSTATS
379/*
380 * mstats - print out statistics about malloc
381 *
382 * Prints two lines of numbers, one showing the length of the free list
383 * for each size category, the second showing the number of mallocs -
384 * frees for each size category.
385 */
386mstats(s)
387 char *s;
388{
389 register int i, j;
390 register union overhead *p;
391 int totfree = 0,
392 totused = 0;
393
394 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
395 for (i = 0; i < NBUCKETS; i++) {
396 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
397 ;
398 fprintf(stderr, " %d", j);
399 totfree += j * (1 << (i + 3));
400 }
401 fprintf(stderr, "\nused:\t");
402 for (i = 0; i < NBUCKETS; i++) {
403 fprintf(stderr, " %d", nmalloc[i]);
404 totused += nmalloc[i] * (1 << (i + 3));
405 }
406 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
407 totused, totfree);
408}
409#endif
a687059c 410#endif /* lint */