lib/malloc.c

   1 /* dynamic memory allocation for GNU.
   2    Copyright (C) 1985, 1987 Free Software Foundation, Inc.
   3
   4                        NO WARRANTY
   5
   6   BECAUSE THIS PROGRAM IS LICENSED FREE OF CHARGE, WE PROVIDE ABSOLUTELY
   7 NO WARRANTY, TO THE EXTENT PERMITTED BY APPLICABLE STATE LAW.  EXCEPT
   8 WHEN OTHERWISE STATED IN WRITING, FREE SOFTWARE FOUNDATION, INC,
   9 RICHARD M. STALLMAN AND/OR OTHER PARTIES PROVIDE THIS PROGRAM "AS IS"
  10 WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING,
  11 BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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  14 DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR
  15 CORRECTION.
  16
  17  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW WILL RICHARD M.
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  19 WHO MAY MODIFY AND REDISTRIBUTE THIS PROGRAM AS PERMITTED BELOW, BE
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  27
  28                 GENERAL PUBLIC LICENSE TO COPY
  29
  30   1. You may copy and distribute verbatim copies of this source file
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  33 (C) 1985 Free Software Foundation, Inc."; and include following the
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  55
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  84   4. You may not copy, sublicense, distribute or transfer this program
  85 except as expressly provided under this License Agreement.  Any attempt
  86 otherwise to copy, sublicense, distribute or transfer this program is void and
  87 your rights to use the program under this License agreement shall be
  88 automatically terminated.  However, parties who have received computer
  89 software programs from you with this License Agreement will not have
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  92   5. If you wish to incorporate parts of this program into other free
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 100
 101 In other words, you are welcome to use, share and improve this program.
 102 You are forbidden to forbid anyone else to use, share and improve
 103 what you give them.   Help stamp out software-hoarding!  */
 104
 105
 106 /*
 107  * @(#)nmalloc.c 1 (Caltech) 2/21/82
 108  *
 109  *      U of M Modified: 20 Jun 1983 ACT: strange hacks for Emacs
 110  *
 111  *      Nov 1983, Mike@BRL, Added support for 4.1C/4.2 BSD.
 112  *
 113  * This is a very fast storage allocator.  It allocates blocks of a small
 114  * number of different sizes, and keeps free lists of each size.  Blocks
 115  * that don't exactly fit are passed up to the next larger size.  In this
 116  * implementation, the available sizes are (2^n)-4 (or -16) bytes long.
 117  * This is designed for use in a program that uses vast quantities of
 118  * memory, but bombs when it runs out.  To make it a little better, it
 119  * warns the user when he starts to get near the end.
 120  *
 121  * June 84, ACT: modified rcheck code to check the range given to malloc,
 122  * rather than the range determined by the 2-power used.
 123  *
 124  * Jan 85, RMS: calls malloc_warning to issue warning on nearly full.
 125  * No longer Emacs-specific; can serve as all-purpose malloc for GNU.
 126  * You should call malloc_init to reinitialize after loading dumped Emacs.
 127  * Call malloc_stats to get info on memory stats if MSTATS turned on.
 128  * realloc knows how to return same block given, just changing its size,
 129  * if the power of 2 is correct.
 130  */
 131
 132 /*
 133  * nextf[i] is the pointer to the next free block of size 2^(i+3).  The
 134  * smallest allocatable block is 8 bytes.  The overhead information will
 135  * go in the first int of the block, and the returned pointer will point
 136  * to the second.
 137  *
 138 #ifdef MSTATS
 139  * nmalloc[i] is the difference between the number of mallocs and frees
 140  * for a given block size.
 141 #endif MSTATS
 142  */
 143
 144 #ifdef emacs
 145 /* config.h specifies which kind of system this is.  */
 146 #include "config.h"
 147 #else
 148
 149 /* Determine which kind of system this is.  */
 150 #include <signal.h>
 151 #ifndef SIGTSTP
 152 #ifndef VMS
 153 #ifndef USG
 154 #define USG
 155 #endif
 156 #endif /* not VMS */
 157 #else /* SIGTSTP */
 158 #ifdef SIGIO
 159 #define BSD4_2
 160 #endif /* SIGIO */
 161 #endif /* SIGTSTP */
 162
 163 #endif /* not emacs */
 164
 165 /* Define getpagesize () if the system does not.  */
 166 #include "getpagesize.h"
 167
 168 #ifndef BSD4_2
 169 #ifndef USG
 170 #include <sys/vlimit.h>         /* warn the user when near the end */
 171 #endif /* not USG */
 172 #else /* if BSD4_2 */
 173 #include <sys/time.h>
 174 #include <sys/resource.h>
 175 #endif /* BSD4_2 */
 176
 177 #ifdef USG
 178 #define bcopy(from, to, n) memcpy(to, from, n)
 179 #endif
 180
 181 extern char *start_of_data ();
 182
 183 #ifdef BSD
 184 #ifndef DATA_SEG_BITS
 185 #define start_of_data() &etext
 186 #endif
 187 #endif
 188
 189 #ifndef emacs
 190 #define start_of_data() &etext
 191 #endif
 192
 193 #define ISALLOC ((char) 0xf7)   /* magic byte that implies allocation */
 194 #define ISFREE ((char) 0x54)    /* magic byte that implies free block */
 195                                 /* this is for error checking only */
 196 #define ISMEMALIGN ((char) 0xd6)  /* Stored before the value returned by
 197                                      memalign, with the rest of the word
 198                                      being the distance to the true
 199                                      beginning of the block.  */
 200
 201 extern char etext;
 202
 203 /* These two are for user programs to look at, when they are interested.  */
 204
 205 unsigned int malloc_sbrk_used;       /* amount of data space used now */
 206 unsigned int malloc_sbrk_unused;     /* amount more we can have */
 207
 208 /* start of data space; can be changed by calling init_malloc */
 209 static char *data_space_start;
 210
 211 #ifdef MSTATS
 212 static int nmalloc[30];
 213 static int nmal, nfre;
 214 #endif /* MSTATS */
 215
 216 /* If range checking is not turned on, all we have is a flag indicating
 217    whether memory is allocated, an index in nextf[], and a size field; to
 218    realloc() memory we copy either size bytes or 1<<(index+3) bytes depending
 219    on whether the former can hold the exact size (given the value of
 220    'index').  If range checking is on, we always need to know how much space
 221    is allocated, so the 'size' field is never used. */
 222
 223 struct mhead {
 224         char     mh_alloc;      /* ISALLOC or ISFREE */
 225         char     mh_index;      /* index in nextf[] */
 226 /* Remainder are valid only when block is allocated */
 227         unsigned short mh_size; /* size, if < 0x10000 */
 228 #ifdef rcheck
 229         unsigned mh_nbytes;     /* number of bytes allocated */
 230         int      mh_magic4;     /* should be == MAGIC4 */
 231 #endif /* rcheck */
 232 };
 233
 234 /* Access free-list pointer of a block.
 235   It is stored at block + 4.
 236   This is not a field in the mhead structure
 237   because we want sizeof (struct mhead)
 238   to describe the overhead for when the block is in use,
 239   and we do not want the free-list pointer to count in that.  */
 240
 241 #define CHAIN(a) \
 242   (*(struct mhead **) (sizeof (char *) + (char *) (a)))
 243
 244 #ifdef rcheck
 245
 246 /* To implement range checking, we write magic values in at the beginning and
 247    end of each allocated block, and make sure they are undisturbed whenever a
 248    free or a realloc occurs. */
 249 /* Written in each of the 4 bytes following the block's real space */
 250 #define MAGIC1 0x55
 251 /* Written in the 4 bytes before the block's real space */
 252 #define MAGIC4 0x55555555
 253 #define ASSERT(p) if (!(p)) botch("p"); else
 254 #define EXTRA  4                /* 4 bytes extra for MAGIC1s */
 255 #else
 256 #define ASSERT(p)
 257 #define EXTRA  0
 258 #endif /* rcheck */
 259
 260
 261 /* nextf[i] is free list of blocks of size 2**(i + 3)  */
 262
 263 static struct mhead *nextf[30];
 264
 265 /* busy[i] is nonzero while allocation of block size i is in progress.  */
 266
 267 static char busy[30];
 268
 269 /* Number of bytes of writable memory we can expect to be able to get */
 270 static unsigned int lim_data;
 271
 272 /* Level number of warnings already issued.
 273   0 -- no warnings issued.
 274   1 -- 75% warning already issued.
 275   2 -- 85% warning already issued.
 276 */
 277 static int warnlevel;
 278
 279 /* Function to call to issue a warning;
 280    0 means don't issue them.  */
 281 static void (*warnfunction) ();
 282
 283 /* nonzero once initial bunch of free blocks made */
 284 static int gotpool;
 285
 286 char *_malloc_base;
 287
 288 static void getpool ();
 289
 290 /* Cause reinitialization based on job parameters;
 291   also declare where the end of pure storage is. */
 292 void
 293 malloc_init (start, warnfun)
 294      char *start;
 295      void (*warnfun) ();
 296 {
 297   if (start)
 298     data_space_start = start;
 299   lim_data = 0;
 300   warnlevel = 0;
 301   warnfunction = warnfun;
 302 }
 303
 304 /* Return the maximum size to which MEM can be realloc'd
 305    without actually requiring copying.  */
 306
 307 int
 308 malloc_usable_size (mem)
 309      char *mem;
 310 {
 311   int blocksize = 8 << (((struct mhead *) mem) - 1) -> mh_index;
 312
 313   return blocksize - sizeof (struct mhead) - EXTRA;
 314 }
 315 \f
 316 static void
 317 morecore (nu)                   /* ask system for more memory */
 318      register int nu;           /* size index to get more of  */
 319 {
 320   char *sbrk ();
 321   register char *cp;
 322   register int nblks;
 323   register unsigned int siz;
 324   int oldmask;
 325
 326 #ifdef BSD
 327 #ifndef BSD4_1
 328   /* ?? There was a suggestion not to block SIGILL, somehow for GDB's sake.  */
 329   oldmask = sigsetmask (-1);
 330 #endif
 331 #endif
 332
 333   if (!data_space_start)
 334     {
 335       data_space_start = start_of_data ();
 336     }
 337
 338   if (lim_data == 0)
 339     get_lim_data ();
 340
 341  /* On initial startup, get two blocks of each size up to 1k bytes */
 342   if (!gotpool)
 343     { getpool (); getpool (); gotpool = 1; }
 344
 345   /* Find current end of memory and issue warning if getting near max */
 346
 347 #ifndef VMS
 348   /* Maximum virtual memory on VMS is difficult to calculate since it
 349    * depends on several dynmacially changing things. Also, alignment
 350    * isn't that important. That is why much of the code here is ifdef'ed
 351    * out for VMS systems.
 352    */
 353   cp = sbrk (0);
 354   siz = cp - data_space_start;
 355
 356   if (warnfunction)
 357     switch (warnlevel)
 358       {
 359       case 0:
 360         if (siz > (lim_data / 4) * 3)
 361           {
 362             warnlevel++;
 363             (*warnfunction) ("Warning: past 75% of memory limit");
 364           }
 365         break;
 366       case 1:
 367         if (siz > (lim_data / 20) * 17)
 368           {
 369             warnlevel++;
 370             (*warnfunction) ("Warning: past 85% of memory limit");
 371           }
 372         break;
 373       case 2:
 374         if (siz > (lim_data / 20) * 19)
 375           {
 376             warnlevel++;
 377             (*warnfunction) ("Warning: past 95% of memory limit");
 378           }
 379         break;
 380       }
 381
 382   if ((int) cp & 0x3ff) /* land on 1K boundaries */
 383     sbrk (1024 - ((int) cp & 0x3ff));
 384 #endif /* not VMS */
 385
 386  /* Take at least 2k, and figure out how many blocks of the desired size
 387     we're about to get */
 388   nblks = 1;
 389   if ((siz = nu) < 8)
 390     nblks = 1 << ((siz = 8) - nu);
 391
 392   if ((cp = sbrk (1 << (siz + 3))) == (char *) -1)
 393     {
 394 #ifdef BSD
 395 #ifndef BSD4_1
 396       sigsetmask (oldmask);
 397 #endif
 398 #endif
 399       return;                   /* no more room! */
 400     }
 401   malloc_sbrk_used = siz;
 402   malloc_sbrk_unused = lim_data - siz;
 403
 404 #ifndef VMS
 405   if ((int) cp & 7)
 406     {           /* shouldn't happen, but just in case */
 407       cp = (char *) (((int) cp + 8) & ~7);
 408       nblks--;
 409     }
 410 #endif /* not VMS */
 411
 412  /* save new header and link the nblks blocks together */
 413   nextf[nu] = (struct mhead *) cp;
 414   siz = 1 << (nu + 3);
 415   while (1)
 416     {
 417       ((struct mhead *) cp) -> mh_alloc = ISFREE;
 418       ((struct mhead *) cp) -> mh_index = nu;
 419       if (--nblks <= 0) break;
 420       CHAIN ((struct mhead *) cp) = (struct mhead *) (cp + siz);
 421       cp += siz;
 422     }
 423   CHAIN ((struct mhead *) cp) = 0;
 424
 425 #ifdef BSD
 426 #ifndef BSD4_1
 427   sigsetmask (oldmask);
 428 #endif
 429 #endif
 430 }
 431
 432 static void
 433 getpool ()
 434 {
 435   register int nu;
 436   char * sbrk ();
 437   register char *cp = sbrk (0);
 438
 439   if ((int) cp & 0x3ff) /* land on 1K boundaries */
 440     sbrk (1024 - ((int) cp & 0x3ff));
 441
 442   /* Record address of start of space allocated by malloc.  */
 443   if (_malloc_base == 0)
 444     _malloc_base = cp;
 445
 446   /* Get 2k of storage */
 447
 448   cp = sbrk (04000);
 449   if (cp == (char *) -1)
 450     return;
 451
 452   /* Divide it into an initial 8-word block
 453      plus one block of size 2**nu for nu = 3 ... 10.  */
 454
 455   CHAIN (cp) = nextf[0];
 456   nextf[0] = (struct mhead *) cp;
 457   ((struct mhead *) cp) -> mh_alloc = ISFREE;
 458   ((struct mhead *) cp) -> mh_index = 0;
 459   cp += 8;
 460
 461   for (nu = 0; nu < 7; nu++)
 462     {
 463       CHAIN (cp) = nextf[nu];
 464       nextf[nu] = (struct mhead *) cp;
 465       ((struct mhead *) cp) -> mh_alloc = ISFREE;
 466       ((struct mhead *) cp) -> mh_index = nu;
 467       cp += 8 << nu;
 468     }
 469 }
 470 \f
 471 char *
 472 malloc (n)              /* get a block */
 473      unsigned n;
 474 {
 475   register struct mhead *p;
 476   register unsigned int nbytes;
 477   register int nunits = 0;
 478
 479   /* Figure out how many bytes are required, rounding up to the nearest
 480      multiple of 8, then figure out which nestf[] area to use.
 481      Both the beginning of the header and the beginning of the
 482      block should be on an eight byte boundary.  */
 483 #ifdef SUNOS_LOCALTIME_BUG
 484   /* SunOS 4.1 localtime scribbles on the ninth byte.  */
 485   nbytes = (n + ((sizeof *p + 15) & ~15) + EXTRA + 15) & ~15;
 486 #else
 487   nbytes = (n + ((sizeof *p + 7) & ~7) + EXTRA + 7) & ~7;
 488 #endif
 489   {
 490     register unsigned int   shiftr = (nbytes - 1) >> 2;
 491
 492     while (shiftr >>= 1)
 493       nunits++;
 494   }
 495
 496   /* In case this is reentrant use of malloc from signal handler,
 497      pick a block size that no other malloc level is currently
 498      trying to allocate.  That's the easiest harmless way not to
 499      interfere with the other level of execution.  */
 500   while (busy[nunits]) nunits++;
 501   busy[nunits] = 1;
 502
 503   /* If there are no blocks of the appropriate size, go get some */
 504   /* COULD SPLIT UP A LARGER BLOCK HERE ... ACT */
 505   if (nextf[nunits] == 0)
 506     morecore (nunits);
 507
 508   /* Get one block off the list, and set the new list head */
 509   if ((p = nextf[nunits]) == 0)
 510     {
 511       busy[nunits] = 0;
 512       return 0;
 513     }
 514   nextf[nunits] = CHAIN (p);
 515   busy[nunits] = 0;
 516
 517   /* Check for free block clobbered */
 518   /* If not for this check, we would gobble a clobbered free chain ptr */
 519   /* and bomb out on the NEXT allocate of this size block */
 520   if (p -> mh_alloc != ISFREE || p -> mh_index != nunits)
 521 #ifdef rcheck
 522     botch ("block on free list clobbered");
 523 #else /* not rcheck */
 524     abort ();
 525 #endif /* not rcheck */
 526
 527   /* Fill in the info, and if range checking, set up the magic numbers */
 528   p -> mh_alloc = ISALLOC;
 529 #ifdef rcheck
 530   p -> mh_nbytes = n;
 531   p -> mh_magic4 = MAGIC4;
 532   {
 533     /* Get the location n after the beginning of the user's space.  */
 534     register char *m = (char *) p + ((sizeof *p + 7) & ~7) + n;
 535
 536     *m++ = MAGIC1, *m++ = MAGIC1, *m++ = MAGIC1, *m = MAGIC1;
 537   }
 538 #else /* not rcheck */
 539   p -> mh_size = n;
 540 #endif /* not rcheck */
 541 #ifdef MSTATS
 542   nmalloc[nunits]++;
 543   nmal++;
 544 #endif /* MSTATS */
 545   return (char *) p + ((sizeof *p + 7) & ~7);
 546 }
 547
 548 free (mem)
 549      char *mem;
 550 {
 551   register struct mhead *p;
 552   {
 553     register char *ap = mem;
 554
 555     if (ap == 0)
 556       return;
 557
 558     p = (struct mhead *) (ap - ((sizeof *p + 7) & ~7));
 559     if (p -> mh_alloc == ISMEMALIGN)
 560       {
 561         ap -= p->mh_size;
 562         p = (struct mhead *) (ap - ((sizeof *p + 7) & ~7));
 563       }
 564
 565 #ifndef rcheck
 566     if (p -> mh_alloc != ISALLOC)
 567       abort ();
 568
 569 #else rcheck
 570     if (p -> mh_alloc != ISALLOC)
 571       {
 572         if (p -> mh_alloc == ISFREE)
 573           botch ("free: Called with already freed block argument\n");
 574         else
 575           botch ("free: Called with bad argument\n");
 576       }
 577
 578     ASSERT (p -> mh_magic4 == MAGIC4);
 579     ap += p -> mh_nbytes;
 580     ASSERT (*ap++ == MAGIC1); ASSERT (*ap++ == MAGIC1);
 581     ASSERT (*ap++ == MAGIC1); ASSERT (*ap   == MAGIC1);
 582 #endif /* rcheck */
 583   }
 584   {
 585     register int nunits = p -> mh_index;
 586
 587     ASSERT (nunits <= 29);
 588     p -> mh_alloc = ISFREE;
 589
 590     /* Protect against signal handlers calling malloc.  */
 591     busy[nunits] = 1;
 592     /* Put this block on the free list.  */
 593     CHAIN (p) = nextf[nunits];
 594     nextf[nunits] = p;
 595     busy[nunits] = 0;
 596
 597 #ifdef MSTATS
 598     nmalloc[nunits]--;
 599     nfre++;
 600 #endif /* MSTATS */
 601   }
 602 }
 603
 604 char *
 605 realloc (mem, n)
 606      char *mem;
 607      register unsigned n;
 608 {
 609   register struct mhead *p;
 610   register unsigned int tocopy;
 611   register unsigned int nbytes;
 612   register int nunits;
 613
 614   if (mem == 0)
 615     return malloc (n);
 616   p = (struct mhead *) (mem - ((sizeof *p + 7) & ~7));
 617   nunits = p -> mh_index;
 618   ASSERT (p -> mh_alloc == ISALLOC);
 619 #ifdef rcheck
 620   ASSERT (p -> mh_magic4 == MAGIC4);
 621   {
 622     register char *m = mem + (tocopy = p -> mh_nbytes);
 623     ASSERT (*m++ == MAGIC1); ASSERT (*m++ == MAGIC1);
 624     ASSERT (*m++ == MAGIC1); ASSERT (*m   == MAGIC1);
 625   }
 626 #else /* not rcheck */
 627   if (p -> mh_index >= 13)
 628     tocopy = (1 << (p -> mh_index + 3)) - ((sizeof *p + 7) & ~7);
 629   else
 630     tocopy = p -> mh_size;
 631 #endif /* not rcheck */
 632
 633   /* See if desired size rounds to same power of 2 as actual size. */
 634   nbytes = (n + ((sizeof *p + 7) & ~7) + EXTRA + 7) & ~7;
 635
 636   /* If ok, use the same block, just marking its size as changed.  */
 637   if (nbytes > (4 << nunits) && nbytes <= (8 << nunits))
 638     {
 639 #ifdef rcheck
 640       register char *m = mem + tocopy;
 641       *m++ = 0;  *m++ = 0;  *m++ = 0;  *m++ = 0;
 642       p-> mh_nbytes = n;
 643       m = mem + n;
 644       *m++ = MAGIC1;  *m++ = MAGIC1;  *m++ = MAGIC1;  *m++ = MAGIC1;
 645 #else /* not rcheck */
 646       p -> mh_size = n;
 647 #endif /* not rcheck */
 648       return mem;
 649     }
 650
 651   if (n < tocopy)
 652     tocopy = n;
 653   {
 654     register char *new;
 655
 656     if ((new = malloc (n)) == 0)
 657       return 0;
 658     bcopy (mem, new, tocopy);
 659     free (mem);
 660     return new;
 661   }
 662 }
 663
 664 #ifndef VMS
 665
 666 char *
 667 memalign (alignment, size)
 668      unsigned alignment, size;
 669 {
 670   register char *ptr = malloc (size + alignment);
 671   register char *aligned;
 672   register struct mhead *p;
 673
 674   if (ptr == 0)
 675     return 0;
 676   /* If entire block has the desired alignment, just accept it.  */
 677   if (((int) ptr & (alignment - 1)) == 0)
 678     return ptr;
 679   /* Otherwise, get address of byte in the block that has that alignment.  */
 680   aligned = (char *) (((int) ptr + alignment - 1) & -alignment);
 681
 682   /* Store a suitable indication of how to free the block,
 683      so that free can find the true beginning of it.  */
 684   p = (struct mhead *) aligned - 1;
 685   p -> mh_size = aligned - ptr;
 686   p -> mh_alloc = ISMEMALIGN;
 687   return aligned;
 688 }
 689
 690 #ifndef HPUX
 691 /* This runs into trouble with getpagesize on HPUX.
 692    Patching out seems cleaner than the ugly fix needed.  */
 693 char *
 694 valloc (size)
 695 {
 696   return memalign (getpagesize (), size);
 697 }
 698 #endif /* not HPUX */
 699 #endif /* not VMS */
 700 \f
 701 #ifdef MSTATS
 702 /* Return statistics describing allocation of blocks of size 2**n. */
 703
 704 struct mstats_value
 705   {
 706     int blocksize;
 707     int nfree;
 708     int nused;
 709   };
 710
 711 struct mstats_value
 712 malloc_stats (size)
 713      int size;
 714 {
 715   struct mstats_value v;
 716   register int i;
 717   register struct mhead *p;
 718
 719   v.nfree = 0;
 720
 721   if (size < 0 || size >= 30)
 722     {
 723       v.blocksize = 0;
 724       v.nused = 0;
 725       return v;
 726     }
 727
 728   v.blocksize = 1 << (size + 3);
 729   v.nused = nmalloc[size];
 730
 731   for (p = nextf[size]; p; p = CHAIN (p))
 732     v.nfree++;
 733
 734   return v;
 735 }
 736 int
 737 malloc_mem_used ()
 738 {
 739   int i;
 740   int size_used;
 741
 742   size_used = 0;
 743
 744   for (i = 0; i < 30; i++)
 745     {
 746       int allocation_size = 1 << (i + 3);
 747       struct mhead *p;
 748
 749       size_used += nmalloc[i] * allocation_size;
 750     }
 751
 752   return size_used;
 753 }
 754
 755 int
 756 malloc_mem_free ()
 757 {
 758   int i;
 759   int size_unused;
 760
 761   size_unused = 0;
 762
 763   for (i = 0; i < 30; i++)
 764     {
 765       int allocation_size = 1 << (i + 3);
 766       struct mhead *p;
 767
 768       for (p = nextf[i]; p ; p = CHAIN (p))
 769         size_unused += allocation_size;
 770     }
 771
 772   return size_unused;
 773 }
 774 #endif /* MSTATS */
 775 \f
 776 /*
 777  *      This function returns the total number of bytes that the process
 778  *      will be allowed to allocate via the sbrk(2) system call.  On
 779  *      BSD systems this is the total space allocatable to stack and
 780  *      data.  On USG systems this is the data space only.
 781  */
 782
 783 #ifdef USG
 784
 785 get_lim_data ()
 786 {
 787   extern long ulimit ();
 788
 789 #ifdef ULIMIT_BREAK_VALUE
 790   lim_data = ULIMIT_BREAK_VALUE;
 791 #else
 792   lim_data = ulimit (3, 0);
 793 #endif
 794
 795   lim_data -= (long) data_space_start;
 796 }
 797
 798 #else /* not USG */
 799 #ifndef BSD4_2
 800
 801 get_lim_data ()
 802 {
 803   lim_data = vlimit (LIM_DATA, -1);
 804 }
 805
 806 #else /* BSD4_2 */
 807
 808 get_lim_data ()
 809 {
 810   struct rlimit XXrlimit;
 811
 812   getrlimit (RLIMIT_DATA, &XXrlimit);
 813 #ifdef RLIM_INFINITY
 814   lim_data = XXrlimit.rlim_cur & RLIM_INFINITY; /* soft limit */
 815 #else
 816   lim_data = XXrlimit.rlim_cur; /* soft limit */
 817 #endif
 818 }
 819
 820 #endif /* BSD4_2 */
 821 #endif /* not USG */
 822 \f
 823 #ifdef VMS
 824 /* There is a problem when dumping and restoring things on VMS. Calls
 825  * to SBRK don't necessarily result in contiguous allocation. Dumping
 826  * doesn't work when it isn't. Therefore, we make the initial
 827  * allocation contiguous by allocating a big chunk, and do SBRKs from
 828  * there. Once Emacs has dumped there is no reason to continue
 829  * contiguous allocation, malloc doesn't depend on it.
 830  *
 831  * There is a further problem of using brk and sbrk while using VMS C
 832  * run time library routines malloc, calloc, etc. The documentation
 833  * says that this is a no-no, although I'm not sure why this would be
 834  * a problem. In any case, we remove the necessity to call brk and
 835  * sbrk, by calling calloc (to assure zero filled data) rather than
 836  * sbrk.
 837  *
 838  * VMS_ALLOCATION_SIZE is the size of the allocation array. This
 839  * should be larger than the malloc size before dumping. Making this
 840  * too large will result in the startup procedure slowing down since
 841  * it will require more space and time to map it in.
 842  *
 843  * The value for VMS_ALLOCATION_SIZE in the following define was determined
 844  * by running emacs linked (and a large allocation) with the debugger and
 845  * looking to see how much storage was used. The allocation was 201 pages,
 846  * so I rounded it up to a power of two.
 847  */
 848 #ifndef VMS_ALLOCATION_SIZE
 849 #define VMS_ALLOCATION_SIZE     (512*256)
 850 #endif
 851
 852 /* Use VMS RTL definitions */
 853 #undef sbrk
 854 #undef brk
 855 #undef malloc
 856 int vms_out_initial = 0;
 857 char vms_initial_buffer[VMS_ALLOCATION_SIZE];
 858 static char *vms_current_brk = &vms_initial_buffer;
 859 static char *vms_end_brk = &vms_initial_buffer[VMS_ALLOCATION_SIZE-1];
 860
 861 #include <stdio.h>
 862
 863 char *
 864 sys_sbrk (incr)
 865      int incr;
 866 {
 867   char *sbrk(), *temp, *ptr;
 868
 869   if (vms_out_initial)
 870     {
 871       /* out of initial allocation... */
 872       if (!(temp = malloc (incr)))
 873         temp = (char *) -1;
 874     }
 875   else
 876     {
 877       /* otherwise, go out of our area */
 878       ptr = vms_current_brk + incr; /* new current_brk */
 879       if (ptr <= vms_end_brk)
 880         {
 881           temp = vms_current_brk;
 882           vms_current_brk = ptr;
 883         }
 884       else
 885         {
 886           vms_out_initial = 1;  /* mark as out of initial allocation */
 887           if (!(temp = malloc (incr)))
 888             temp = (char *) -1;
 889         }
 890     }
 891   return temp;
 892 }
 893 #endif /* VMS */