src/lj_alloc.c

   1 /*
   2 ** Bundled memory allocator.
   3 **
   4 ** Beware: this is a HEAVILY CUSTOMIZED version of dlmalloc.
   5 ** The original bears the following remark:
   6 **
   7 **   This is a version (aka dlmalloc) of malloc/free/realloc written by
   8 **   Doug Lea and released to the public domain, as explained at
   9 **   http://creativecommons.org/licenses/publicdomain.
  10 **
  11 **   * Version pre-2.8.4 Wed Mar 29 19:46:29 2006    (dl at gee)
  12 **
  13 ** No additional copyright is claimed over the customizations.
  14 ** Please do NOT bother the original author about this version here!
  15 **
  16 ** If you want to use dlmalloc in another project, you should get
  17 ** the original from: ftp://gee.cs.oswego.edu/pub/misc/
  18 ** For thread-safe derivatives, take a look at:
  19 ** - ptmalloc: http://www.malloc.de/
  20 ** - nedmalloc: http://www.nedprod.com/programs/portable/nedmalloc/
  21 */
  22
  23 #define lj_alloc_c
  24 #define LUA_CORE
  25
  26 /* To get the mremap prototype. Must be defined before any system includes. */
  27 #if defined(__linux__) && !defined(_GNU_SOURCE)
  28 #define _GNU_SOURCE
  29 #endif
  30
  31 #include "lj_def.h"
  32 #include "lj_arch.h"
  33 #include "lj_alloc.h"
  34
  35 #ifndef LUAJIT_USE_SYSMALLOC
  36
  37 #define MAX_SIZE_T              (~(size_t)0)
  38 #define MALLOC_ALIGNMENT        ((size_t)8U)
  39
  40 #define DEFAULT_GRANULARITY     ((size_t)128U * (size_t)1024U)
  41 #define DEFAULT_TRIM_THRESHOLD  ((size_t)2U * (size_t)1024U * (size_t)1024U)
  42 #define DEFAULT_MMAP_THRESHOLD  ((size_t)128U * (size_t)1024U)
  43 #define MAX_RELEASE_CHECK_RATE  255
  44
  45 /* ------------------- size_t and alignment properties -------------------- */
  46
  47 /* The byte and bit size of a size_t */
  48 #define SIZE_T_SIZE             (sizeof(size_t))
  49 #define SIZE_T_BITSIZE          (sizeof(size_t) << 3)
  50
  51 /* Some constants coerced to size_t */
  52 /* Annoying but necessary to avoid errors on some platforms */
  53 #define SIZE_T_ZERO             ((size_t)0)
  54 #define SIZE_T_ONE              ((size_t)1)
  55 #define SIZE_T_TWO              ((size_t)2)
  56 #define TWO_SIZE_T_SIZES        (SIZE_T_SIZE<<1)
  57 #define FOUR_SIZE_T_SIZES       (SIZE_T_SIZE<<2)
  58 #define SIX_SIZE_T_SIZES        (FOUR_SIZE_T_SIZES+TWO_SIZE_T_SIZES)
  59
  60 /* The bit mask value corresponding to MALLOC_ALIGNMENT */
  61 #define CHUNK_ALIGN_MASK        (MALLOC_ALIGNMENT - SIZE_T_ONE)
  62
  63 /* the number of bytes to offset an address to align it */
  64 #define align_offset(A)\
  65  ((((size_t)(A) & CHUNK_ALIGN_MASK) == 0)? 0 :\
  66   ((MALLOC_ALIGNMENT - ((size_t)(A) & CHUNK_ALIGN_MASK)) & CHUNK_ALIGN_MASK))
  67
  68 /* -------------------------- MMAP support ------------------------------- */
  69
  70 #define MFAIL                   ((void *)(MAX_SIZE_T))
  71 #define CMFAIL                  ((char *)(MFAIL)) /* defined for convenience */
  72
  73 #define IS_DIRECT_BIT           (SIZE_T_ONE)
  74
  75 #if LJ_TARGET_WINDOWS
  76
  77 #define WIN32_LEAN_AND_MEAN
  78 #include <windows.h>
  79
  80 #if LJ_64
  81
  82 /* Undocumented, but hey, that's what we all love so much about Windows. */
  83 typedef long (*PNTAVM)(HANDLE handle, void **addr, ULONG zbits,
  84                        size_t *size, ULONG alloctype, ULONG prot);
  85 static PNTAVM ntavm;
  86
  87 /* Number of top bits of the lower 32 bits of an address that must be zero.
  88 ** Apparently 0 gives us full 64 bit addresses and 1 gives us the lower 2GB.
  89 */
  90 #define NTAVM_ZEROBITS          1
  91
  92 static void INIT_MMAP(void)
  93 {
  94   ntavm = (PNTAVM)GetProcAddress(GetModuleHandleA("ntdll.dll"),
  95                                  "NtAllocateVirtualMemory");
  96 }
  97
  98 /* Win64 32 bit MMAP via NtAllocateVirtualMemory. */
  99 static LJ_AINLINE void *CALL_MMAP(size_t size)
 100 {
 101   DWORD olderr = GetLastError();
 102   void *ptr = NULL;
 103   long st = ntavm(INVALID_HANDLE_VALUE, &ptr, NTAVM_ZEROBITS, &size,
 104                   MEM_RESERVE|MEM_COMMIT, PAGE_READWRITE);
 105   SetLastError(olderr);
 106   return st == 0 ? ptr : MFAIL;
 107 }
 108
 109 /* For direct MMAP, use MEM_TOP_DOWN to minimize interference */
 110 static LJ_AINLINE void *DIRECT_MMAP(size_t size)
 111 {
 112   DWORD olderr = GetLastError();
 113   void *ptr = NULL;
 114   long st = ntavm(INVALID_HANDLE_VALUE, &ptr, NTAVM_ZEROBITS, &size,
 115                   MEM_RESERVE|MEM_COMMIT|MEM_TOP_DOWN, PAGE_READWRITE);
 116   SetLastError(olderr);
 117   return st == 0 ? ptr : MFAIL;
 118 }
 119
 120 #else
 121
 122 #define INIT_MMAP()             ((void)0)
 123
 124 /* Win32 MMAP via VirtualAlloc */
 125 static LJ_AINLINE void *CALL_MMAP(size_t size)
 126 {
 127   DWORD olderr = GetLastError();
 128   void *ptr = VirtualAlloc(0, size, MEM_RESERVE|MEM_COMMIT, PAGE_READWRITE);
 129   SetLastError(olderr);
 130   return ptr ? ptr : MFAIL;
 131 }
 132
 133 /* For direct MMAP, use MEM_TOP_DOWN to minimize interference */
 134 static LJ_AINLINE void *DIRECT_MMAP(size_t size)
 135 {
 136   DWORD olderr = GetLastError();
 137   void *ptr = VirtualAlloc(0, size, MEM_RESERVE|MEM_COMMIT|MEM_TOP_DOWN,
 138                            PAGE_READWRITE);
 139   SetLastError(olderr);
 140   return ptr ? ptr : MFAIL;
 141 }
 142
 143 #endif
 144
 145 /* This function supports releasing coalesed segments */
 146 static LJ_AINLINE int CALL_MUNMAP(void *ptr, size_t size)
 147 {
 148   DWORD olderr = GetLastError();
 149   MEMORY_BASIC_INFORMATION minfo;
 150   char *cptr = (char *)ptr;
 151   while (size) {
 152     if (VirtualQuery(cptr, &minfo, sizeof(minfo)) == 0)
 153       return -1;
 154     if (minfo.BaseAddress != cptr || minfo.AllocationBase != cptr ||
 155         minfo.State != MEM_COMMIT || minfo.RegionSize > size)
 156       return -1;
 157     if (VirtualFree(cptr, 0, MEM_RELEASE) == 0)
 158       return -1;
 159     cptr += minfo.RegionSize;
 160     size -= minfo.RegionSize;
 161   }
 162   SetLastError(olderr);
 163   return 0;
 164 }
 165
 166 #else
 167
 168 #include <errno.h>
 169 #include <sys/mman.h>
 170
 171 #define MMAP_PROT               (PROT_READ|PROT_WRITE)
 172 #if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
 173 #define MAP_ANONYMOUS           MAP_ANON
 174 #endif
 175 #define MMAP_FLAGS              (MAP_PRIVATE|MAP_ANONYMOUS)
 176
 177 #if LJ_64
 178 /* 64 bit mode needs special support for allocating memory in the lower 2GB. */
 179
 180 #if LJ_TARGET_LINUX
 181
 182 /* Actually this only gives us max. 1GB in current Linux kernels. */
 183 static LJ_AINLINE void *CALL_MMAP(size_t size)
 184 {
 185   int olderr = errno;
 186   void *ptr = mmap(NULL, size, MMAP_PROT, MAP_32BIT|MMAP_FLAGS, -1, 0);
 187   errno = olderr;
 188   return ptr;
 189 }
 190
 191 #elif LJ_TARGET_OSX || defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__OpenBSD__)
 192
 193 /* OSX and FreeBSD mmap() use a naive first-fit linear search.
 194 ** That's perfect for us. Except that -pagezero_size must be set for OSX,
 195 ** otherwise the lower 4GB are blocked. And the 32GB RLIMIT_DATA needs
 196 ** to be reduced to 250MB on FreeBSD.
 197 */
 198 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__OpenBSD__)
 199 #include <sys/resource.h>
 200 #define MMAP_REGION_START       ((uintptr_t)0x10000000)
 201 #else
 202 #define MMAP_REGION_START       ((uintptr_t)0x10000)
 203 #endif
 204 #define MMAP_REGION_END         ((uintptr_t)0x80000000)
 205
 206 static LJ_AINLINE void *CALL_MMAP(size_t size)
 207 {
 208   int olderr = errno;
 209   /* Hint for next allocation. Doesn't need to be thread-safe. */
 210   static uintptr_t alloc_hint = MMAP_REGION_START;
 211   int retry = 0;
 212 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
 213   static int rlimit_modified = 0;
 214   if (LJ_UNLIKELY(rlimit_modified == 0)) {
 215     struct rlimit rlim;
 216     rlim.rlim_cur = rlim.rlim_max = MMAP_REGION_START;
 217     setrlimit(RLIMIT_DATA, &rlim);  /* Ignore result. May fail below. */
 218     rlimit_modified = 1;
 219   }
 220 #endif
 221   for (;;) {
 222     void *p = mmap((void *)alloc_hint, size, MMAP_PROT, MMAP_FLAGS, -1, 0);
 223     if ((uintptr_t)p >= MMAP_REGION_START &&
 224         (uintptr_t)p + size < MMAP_REGION_END) {
 225       alloc_hint = (uintptr_t)p + size;
 226       errno = olderr;
 227       return p;
 228     }
 229     if (p != CMFAIL) munmap(p, size);
 230     if (retry) break;
 231     retry = 1;
 232     alloc_hint = MMAP_REGION_START;
 233   }
 234   errno = olderr;
 235   return CMFAIL;
 236 }
 237
 238 #else
 239
 240 #error "NYI: need an equivalent of MAP_32BIT for this 64 bit OS"
 241
 242 #endif
 243
 244 #else
 245
 246 /* 32 bit mode is easy. */
 247 static LJ_AINLINE void *CALL_MMAP(size_t size)
 248 {
 249   int olderr = errno;
 250   void *ptr = mmap(NULL, size, MMAP_PROT, MMAP_FLAGS, -1, 0);
 251   errno = olderr;
 252   return ptr;
 253 }
 254
 255 #endif
 256
 257 #define INIT_MMAP()             ((void)0)
 258 #define DIRECT_MMAP(s)          CALL_MMAP(s)
 259
 260 static LJ_AINLINE int CALL_MUNMAP(void *ptr, size_t size)
 261 {
 262   int olderr = errno;
 263   int ret = munmap(ptr, size);
 264   errno = olderr;
 265   return ret;
 266 }
 267
 268 #if LJ_TARGET_LINUX
 269 /* Need to define _GNU_SOURCE to get the mremap prototype. */
 270 static LJ_AINLINE void *CALL_MREMAP_(void *ptr, size_t osz, size_t nsz,
 271                                      int flags)
 272 {
 273   int olderr = errno;
 274   ptr = mremap(ptr, osz, nsz, flags);
 275   errno = olderr;
 276   return ptr;
 277 }
 278
 279 #define CALL_MREMAP(addr, osz, nsz, mv) CALL_MREMAP_((addr), (osz), (nsz), (mv))
 280 #define CALL_MREMAP_NOMOVE      0
 281 #define CALL_MREMAP_MAYMOVE     1
 282 #if LJ_64
 283 #define CALL_MREMAP_MV          CALL_MREMAP_NOMOVE
 284 #else
 285 #define CALL_MREMAP_MV          CALL_MREMAP_MAYMOVE
 286 #endif
 287 #endif
 288
 289 #endif
 290
 291 #ifndef CALL_MREMAP
 292 #define CALL_MREMAP(addr, osz, nsz, mv) ((void)osz, MFAIL)
 293 #endif
 294
 295 /* -----------------------  Chunk representations ------------------------ */
 296
 297 struct malloc_chunk {
 298   size_t               prev_foot;  /* Size of previous chunk (if free).  */
 299   size_t               head;       /* Size and inuse bits. */
 300   struct malloc_chunk *fd;         /* double links -- used only if free. */
 301   struct malloc_chunk *bk;
 302 };
 303
 304 typedef struct malloc_chunk  mchunk;
 305 typedef struct malloc_chunk *mchunkptr;
 306 typedef struct malloc_chunk *sbinptr;  /* The type of bins of chunks */
 307 typedef size_t bindex_t;               /* Described below */
 308 typedef unsigned int binmap_t;         /* Described below */
 309 typedef unsigned int flag_t;           /* The type of various bit flag sets */
 310
 311 /* ------------------- Chunks sizes and alignments ----------------------- */
 312
 313 #define MCHUNK_SIZE             (sizeof(mchunk))
 314
 315 #define CHUNK_OVERHEAD          (SIZE_T_SIZE)
 316
 317 /* Direct chunks need a second word of overhead ... */
 318 #define DIRECT_CHUNK_OVERHEAD   (TWO_SIZE_T_SIZES)
 319 /* ... and additional padding for fake next-chunk at foot */
 320 #define DIRECT_FOOT_PAD         (FOUR_SIZE_T_SIZES)
 321
 322 /* The smallest size we can malloc is an aligned minimal chunk */
 323 #define MIN_CHUNK_SIZE\
 324   ((MCHUNK_SIZE + CHUNK_ALIGN_MASK) & ~CHUNK_ALIGN_MASK)
 325
 326 /* conversion from malloc headers to user pointers, and back */
 327 #define chunk2mem(p)            ((void *)((char *)(p) + TWO_SIZE_T_SIZES))
 328 #define mem2chunk(mem)          ((mchunkptr)((char *)(mem) - TWO_SIZE_T_SIZES))
 329 /* chunk associated with aligned address A */
 330 #define align_as_chunk(A)       (mchunkptr)((A) + align_offset(chunk2mem(A)))
 331
 332 /* Bounds on request (not chunk) sizes. */
 333 #define MAX_REQUEST             ((~MIN_CHUNK_SIZE+1) << 2)
 334 #define MIN_REQUEST             (MIN_CHUNK_SIZE - CHUNK_OVERHEAD - SIZE_T_ONE)
 335
 336 /* pad request bytes into a usable size */
 337 #define pad_request(req) \
 338    (((req) + CHUNK_OVERHEAD + CHUNK_ALIGN_MASK) & ~CHUNK_ALIGN_MASK)
 339
 340 /* pad request, checking for minimum (but not maximum) */
 341 #define request2size(req) \
 342   (((req) < MIN_REQUEST)? MIN_CHUNK_SIZE : pad_request(req))
 343
 344 /* ------------------ Operations on head and foot fields ----------------- */
 345
 346 #define PINUSE_BIT              (SIZE_T_ONE)
 347 #define CINUSE_BIT              (SIZE_T_TWO)
 348 #define INUSE_BITS              (PINUSE_BIT|CINUSE_BIT)
 349
 350 /* Head value for fenceposts */
 351 #define FENCEPOST_HEAD          (INUSE_BITS|SIZE_T_SIZE)
 352
 353 /* extraction of fields from head words */
 354 #define cinuse(p)               ((p)->head & CINUSE_BIT)
 355 #define pinuse(p)               ((p)->head & PINUSE_BIT)
 356 #define chunksize(p)            ((p)->head & ~(INUSE_BITS))
 357
 358 #define clear_pinuse(p)         ((p)->head &= ~PINUSE_BIT)
 359 #define clear_cinuse(p)         ((p)->head &= ~CINUSE_BIT)
 360
 361 /* Treat space at ptr +/- offset as a chunk */
 362 #define chunk_plus_offset(p, s)         ((mchunkptr)(((char *)(p)) + (s)))
 363 #define chunk_minus_offset(p, s)        ((mchunkptr)(((char *)(p)) - (s)))
 364
 365 /* Ptr to next or previous physical malloc_chunk. */
 366 #define next_chunk(p)   ((mchunkptr)(((char *)(p)) + ((p)->head & ~INUSE_BITS)))
 367 #define prev_chunk(p)   ((mchunkptr)(((char *)(p)) - ((p)->prev_foot) ))
 368
 369 /* extract next chunk's pinuse bit */
 370 #define next_pinuse(p)  ((next_chunk(p)->head) & PINUSE_BIT)
 371
 372 /* Get/set size at footer */
 373 #define get_foot(p, s)  (((mchunkptr)((char *)(p) + (s)))->prev_foot)
 374 #define set_foot(p, s)  (((mchunkptr)((char *)(p) + (s)))->prev_foot = (s))
 375
 376 /* Set size, pinuse bit, and foot */
 377 #define set_size_and_pinuse_of_free_chunk(p, s)\
 378   ((p)->head = (s|PINUSE_BIT), set_foot(p, s))
 379
 380 /* Set size, pinuse bit, foot, and clear next pinuse */
 381 #define set_free_with_pinuse(p, s, n)\
 382   (clear_pinuse(n), set_size_and_pinuse_of_free_chunk(p, s))
 383
 384 #define is_direct(p)\
 385   (!((p)->head & PINUSE_BIT) && ((p)->prev_foot & IS_DIRECT_BIT))
 386
 387 /* Get the internal overhead associated with chunk p */
 388 #define overhead_for(p)\
 389  (is_direct(p)? DIRECT_CHUNK_OVERHEAD : CHUNK_OVERHEAD)
 390
 391 /* ---------------------- Overlaid data structures ----------------------- */
 392
 393 struct malloc_tree_chunk {
 394   /* The first four fields must be compatible with malloc_chunk */
 395   size_t                    prev_foot;
 396   size_t                    head;
 397   struct malloc_tree_chunk *fd;
 398   struct malloc_tree_chunk *bk;
 399
 400   struct malloc_tree_chunk *child[2];
 401   struct malloc_tree_chunk *parent;
 402   bindex_t                  index;
 403 };
 404
 405 typedef struct malloc_tree_chunk  tchunk;
 406 typedef struct malloc_tree_chunk *tchunkptr;
 407 typedef struct malloc_tree_chunk *tbinptr; /* The type of bins of trees */
 408
 409 /* A little helper macro for trees */
 410 #define leftmost_child(t) ((t)->child[0] != 0? (t)->child[0] : (t)->child[1])
 411
 412 /* ----------------------------- Segments -------------------------------- */
 413
 414 struct malloc_segment {
 415   char        *base;             /* base address */
 416   size_t       size;             /* allocated size */
 417   struct malloc_segment *next;   /* ptr to next segment */
 418 };
 419
 420 typedef struct malloc_segment  msegment;
 421 typedef struct malloc_segment *msegmentptr;
 422
 423 /* ---------------------------- malloc_state ----------------------------- */
 424
 425 /* Bin types, widths and sizes */
 426 #define NSMALLBINS              (32U)
 427 #define NTREEBINS               (32U)
 428 #define SMALLBIN_SHIFT          (3U)
 429 #define SMALLBIN_WIDTH          (SIZE_T_ONE << SMALLBIN_SHIFT)
 430 #define TREEBIN_SHIFT           (8U)
 431 #define MIN_LARGE_SIZE          (SIZE_T_ONE << TREEBIN_SHIFT)
 432 #define MAX_SMALL_SIZE          (MIN_LARGE_SIZE - SIZE_T_ONE)
 433 #define MAX_SMALL_REQUEST  (MAX_SMALL_SIZE - CHUNK_ALIGN_MASK - CHUNK_OVERHEAD)
 434
 435 struct malloc_state {
 436   binmap_t   smallmap;
 437   binmap_t   treemap;
 438   size_t     dvsize;
 439   size_t     topsize;
 440   mchunkptr  dv;
 441   mchunkptr  top;
 442   size_t     trim_check;
 443   size_t     release_checks;
 444   mchunkptr  smallbins[(NSMALLBINS+1)*2];
 445   tbinptr    treebins[NTREEBINS];
 446   msegment   seg;
 447 };
 448
 449 typedef struct malloc_state *mstate;
 450
 451 #define is_initialized(M)       ((M)->top != 0)
 452
 453 /* -------------------------- system alloc setup ------------------------- */
 454
 455 /* page-align a size */
 456 #define page_align(S)\
 457  (((S) + (LJ_PAGESIZE - SIZE_T_ONE)) & ~(LJ_PAGESIZE - SIZE_T_ONE))
 458
 459 /* granularity-align a size */
 460 #define granularity_align(S)\
 461   (((S) + (DEFAULT_GRANULARITY - SIZE_T_ONE))\
 462    & ~(DEFAULT_GRANULARITY - SIZE_T_ONE))
 463
 464 #if LJ_TARGET_WINDOWS
 465 #define mmap_align(S)   granularity_align(S)
 466 #else
 467 #define mmap_align(S)   page_align(S)
 468 #endif
 469
 470 /*  True if segment S holds address A */
 471 #define segment_holds(S, A)\
 472   ((char *)(A) >= S->base && (char *)(A) < S->base + S->size)
 473
 474 /* Return segment holding given address */
 475 static msegmentptr segment_holding(mstate m, char *addr)
 476 {
 477   msegmentptr sp = &m->seg;
 478   for (;;) {
 479     if (addr >= sp->base && addr < sp->base + sp->size)
 480       return sp;
 481     if ((sp = sp->next) == 0)
 482       return 0;
 483   }
 484 }
 485
 486 /* Return true if segment contains a segment link */
 487 static int has_segment_link(mstate m, msegmentptr ss)
 488 {
 489   msegmentptr sp = &m->seg;
 490   for (;;) {
 491     if ((char *)sp >= ss->base && (char *)sp < ss->base + ss->size)
 492       return 1;
 493     if ((sp = sp->next) == 0)
 494       return 0;
 495   }
 496 }
 497
 498 /*
 499   TOP_FOOT_SIZE is padding at the end of a segment, including space
 500   that may be needed to place segment records and fenceposts when new
 501   noncontiguous segments are added.
 502 */
 503 #define TOP_FOOT_SIZE\
 504   (align_offset(chunk2mem(0))+pad_request(sizeof(struct malloc_segment))+MIN_CHUNK_SIZE)
 505
 506 /* ---------------------------- Indexing Bins ---------------------------- */
 507
 508 #define is_small(s)             (((s) >> SMALLBIN_SHIFT) < NSMALLBINS)
 509 #define small_index(s)          ((s)  >> SMALLBIN_SHIFT)
 510 #define small_index2size(i)     ((i)  << SMALLBIN_SHIFT)
 511 #define MIN_SMALL_INDEX         (small_index(MIN_CHUNK_SIZE))
 512
 513 /* addressing by index. See above about smallbin repositioning */
 514 #define smallbin_at(M, i)       ((sbinptr)((char *)&((M)->smallbins[(i)<<1])))
 515 #define treebin_at(M,i)         (&((M)->treebins[i]))
 516
 517 /* assign tree index for size S to variable I */
 518 #define compute_tree_index(S, I)\
 519 {\
 520   unsigned int X = (unsigned int)(S >> TREEBIN_SHIFT);\
 521   if (X == 0) {\
 522     I = 0;\
 523   } else if (X > 0xFFFF) {\
 524     I = NTREEBINS-1;\
 525   } else {\
 526     unsigned int K = lj_fls(X);\
 527     I =  (bindex_t)((K << 1) + ((S >> (K + (TREEBIN_SHIFT-1)) & 1)));\
 528   }\
 529 }
 530
 531 /* Bit representing maximum resolved size in a treebin at i */
 532 #define bit_for_tree_index(i) \
 533    (i == NTREEBINS-1)? (SIZE_T_BITSIZE-1) : (((i) >> 1) + TREEBIN_SHIFT - 2)
 534
 535 /* Shift placing maximum resolved bit in a treebin at i as sign bit */
 536 #define leftshift_for_tree_index(i) \
 537    ((i == NTREEBINS-1)? 0 : \
 538     ((SIZE_T_BITSIZE-SIZE_T_ONE) - (((i) >> 1) + TREEBIN_SHIFT - 2)))
 539
 540 /* The size of the smallest chunk held in bin with index i */
 541 #define minsize_for_tree_index(i) \
 542    ((SIZE_T_ONE << (((i) >> 1) + TREEBIN_SHIFT)) |  \
 543    (((size_t)((i) & SIZE_T_ONE)) << (((i) >> 1) + TREEBIN_SHIFT - 1)))
 544
 545 /* ------------------------ Operations on bin maps ----------------------- */
 546
 547 /* bit corresponding to given index */
 548 #define idx2bit(i)              ((binmap_t)(1) << (i))
 549
 550 /* Mark/Clear bits with given index */
 551 #define mark_smallmap(M,i)      ((M)->smallmap |=  idx2bit(i))
 552 #define clear_smallmap(M,i)     ((M)->smallmap &= ~idx2bit(i))
 553 #define smallmap_is_marked(M,i) ((M)->smallmap &   idx2bit(i))
 554
 555 #define mark_treemap(M,i)       ((M)->treemap  |=  idx2bit(i))
 556 #define clear_treemap(M,i)      ((M)->treemap  &= ~idx2bit(i))
 557 #define treemap_is_marked(M,i)  ((M)->treemap  &   idx2bit(i))
 558
 559 /* mask with all bits to left of least bit of x on */
 560 #define left_bits(x)            ((x<<1) | (~(x<<1)+1))
 561
 562 /* Set cinuse bit and pinuse bit of next chunk */
 563 #define set_inuse(M,p,s)\
 564   ((p)->head = (((p)->head & PINUSE_BIT)|s|CINUSE_BIT),\
 565   ((mchunkptr)(((char *)(p)) + (s)))->head |= PINUSE_BIT)
 566
 567 /* Set cinuse and pinuse of this chunk and pinuse of next chunk */
 568 #define set_inuse_and_pinuse(M,p,s)\
 569   ((p)->head = (s|PINUSE_BIT|CINUSE_BIT),\
 570   ((mchunkptr)(((char *)(p)) + (s)))->head |= PINUSE_BIT)
 571
 572 /* Set size, cinuse and pinuse bit of this chunk */
 573 #define set_size_and_pinuse_of_inuse_chunk(M, p, s)\
 574   ((p)->head = (s|PINUSE_BIT|CINUSE_BIT))
 575
 576 /* ----------------------- Operations on smallbins ----------------------- */
 577
 578 /* Link a free chunk into a smallbin  */
 579 #define insert_small_chunk(M, P, S) {\
 580   bindex_t I = small_index(S);\
 581   mchunkptr B = smallbin_at(M, I);\
 582   mchunkptr F = B;\
 583   if (!smallmap_is_marked(M, I))\
 584     mark_smallmap(M, I);\
 585   else\
 586     F = B->fd;\
 587   B->fd = P;\
 588   F->bk = P;\
 589   P->fd = F;\
 590   P->bk = B;\
 591 }
 592
 593 /* Unlink a chunk from a smallbin  */
 594 #define unlink_small_chunk(M, P, S) {\
 595   mchunkptr F = P->fd;\
 596   mchunkptr B = P->bk;\
 597   bindex_t I = small_index(S);\
 598   if (F == B) {\
 599     clear_smallmap(M, I);\
 600   } else {\
 601     F->bk = B;\
 602     B->fd = F;\
 603   }\
 604 }
 605
 606 /* Unlink the first chunk from a smallbin */
 607 #define unlink_first_small_chunk(M, B, P, I) {\
 608   mchunkptr F = P->fd;\
 609   if (B == F) {\
 610     clear_smallmap(M, I);\
 611   } else {\
 612     B->fd = F;\
 613     F->bk = B;\
 614   }\
 615 }
 616
 617 /* Replace dv node, binning the old one */
 618 /* Used only when dvsize known to be small */
 619 #define replace_dv(M, P, S) {\
 620   size_t DVS = M->dvsize;\
 621   if (DVS != 0) {\
 622     mchunkptr DV = M->dv;\
 623     insert_small_chunk(M, DV, DVS);\
 624   }\
 625   M->dvsize = S;\
 626   M->dv = P;\
 627 }
 628
 629 /* ------------------------- Operations on trees ------------------------- */
 630
 631 /* Insert chunk into tree */
 632 #define insert_large_chunk(M, X, S) {\
 633   tbinptr *H;\
 634   bindex_t I;\
 635   compute_tree_index(S, I);\
 636   H = treebin_at(M, I);\
 637   X->index = I;\
 638   X->child[0] = X->child[1] = 0;\
 639   if (!treemap_is_marked(M, I)) {\
 640     mark_treemap(M, I);\
 641     *H = X;\
 642     X->parent = (tchunkptr)H;\
 643     X->fd = X->bk = X;\
 644   } else {\
 645     tchunkptr T = *H;\
 646     size_t K = S << leftshift_for_tree_index(I);\
 647     for (;;) {\
 648       if (chunksize(T) != S) {\
 649         tchunkptr *C = &(T->child[(K >> (SIZE_T_BITSIZE-SIZE_T_ONE)) & 1]);\
 650         K <<= 1;\
 651         if (*C != 0) {\
 652           T = *C;\
 653         } else {\
 654           *C = X;\
 655           X->parent = T;\
 656           X->fd = X->bk = X;\
 657           break;\
 658         }\
 659       } else {\
 660         tchunkptr F = T->fd;\
 661         T->fd = F->bk = X;\
 662         X->fd = F;\
 663         X->bk = T;\
 664         X->parent = 0;\
 665         break;\
 666       }\
 667     }\
 668   }\
 669 }
 670
 671 #define unlink_large_chunk(M, X) {\
 672   tchunkptr XP = X->parent;\
 673   tchunkptr R;\
 674   if (X->bk != X) {\
 675     tchunkptr F = X->fd;\
 676     R = X->bk;\
 677     F->bk = R;\
 678     R->fd = F;\
 679   } else {\
 680     tchunkptr *RP;\
 681     if (((R = *(RP = &(X->child[1]))) != 0) ||\
 682         ((R = *(RP = &(X->child[0]))) != 0)) {\
 683       tchunkptr *CP;\
 684       while ((*(CP = &(R->child[1])) != 0) ||\
 685              (*(CP = &(R->child[0])) != 0)) {\
 686         R = *(RP = CP);\
 687       }\
 688       *RP = 0;\
 689     }\
 690   }\
 691   if (XP != 0) {\
 692     tbinptr *H = treebin_at(M, X->index);\
 693     if (X == *H) {\
 694       if ((*H = R) == 0) \
 695         clear_treemap(M, X->index);\
 696     } else {\
 697       if (XP->child[0] == X) \
 698         XP->child[0] = R;\
 699       else \
 700         XP->child[1] = R;\
 701     }\
 702     if (R != 0) {\
 703       tchunkptr C0, C1;\
 704       R->parent = XP;\
 705       if ((C0 = X->child[0]) != 0) {\
 706         R->child[0] = C0;\
 707         C0->parent = R;\
 708       }\
 709       if ((C1 = X->child[1]) != 0) {\
 710         R->child[1] = C1;\
 711         C1->parent = R;\
 712       }\
 713     }\
 714   }\
 715 }
 716
 717 /* Relays to large vs small bin operations */
 718
 719 #define insert_chunk(M, P, S)\
 720   if (is_small(S)) { insert_small_chunk(M, P, S)\
 721   } else { tchunkptr TP = (tchunkptr)(P); insert_large_chunk(M, TP, S); }
 722
 723 #define unlink_chunk(M, P, S)\
 724   if (is_small(S)) { unlink_small_chunk(M, P, S)\
 725   } else { tchunkptr TP = (tchunkptr)(P); unlink_large_chunk(M, TP); }
 726
 727 /* -----------------------  Direct-mmapping chunks ----------------------- */
 728
 729 static void *direct_alloc(size_t nb)
 730 {
 731   size_t mmsize = mmap_align(nb + SIX_SIZE_T_SIZES + CHUNK_ALIGN_MASK);
 732   if (LJ_LIKELY(mmsize > nb)) {     /* Check for wrap around 0 */
 733     char *mm = (char *)(DIRECT_MMAP(mmsize));
 734     if (mm != CMFAIL) {
 735       size_t offset = align_offset(chunk2mem(mm));
 736       size_t psize = mmsize - offset - DIRECT_FOOT_PAD;
 737       mchunkptr p = (mchunkptr)(mm + offset);
 738       p->prev_foot = offset | IS_DIRECT_BIT;
 739       p->head = psize|CINUSE_BIT;
 740       chunk_plus_offset(p, psize)->head = FENCEPOST_HEAD;
 741       chunk_plus_offset(p, psize+SIZE_T_SIZE)->head = 0;
 742       return chunk2mem(p);
 743     }
 744   }
 745   return NULL;
 746 }
 747
 748 static mchunkptr direct_resize(mchunkptr oldp, size_t nb)
 749 {
 750   size_t oldsize = chunksize(oldp);
 751   if (is_small(nb)) /* Can't shrink direct regions below small size */
 752     return NULL;
 753   /* Keep old chunk if big enough but not too big */
 754   if (oldsize >= nb + SIZE_T_SIZE &&
 755       (oldsize - nb) <= (DEFAULT_GRANULARITY << 1)) {
 756     return oldp;
 757   } else {
 758     size_t offset = oldp->prev_foot & ~IS_DIRECT_BIT;
 759     size_t oldmmsize = oldsize + offset + DIRECT_FOOT_PAD;
 760     size_t newmmsize = mmap_align(nb + SIX_SIZE_T_SIZES + CHUNK_ALIGN_MASK);
 761     char *cp = (char *)CALL_MREMAP((char *)oldp - offset,
 762                                    oldmmsize, newmmsize, CALL_MREMAP_MV);
 763     if (cp != CMFAIL) {
 764       mchunkptr newp = (mchunkptr)(cp + offset);
 765       size_t psize = newmmsize - offset - DIRECT_FOOT_PAD;
 766       newp->head = psize|CINUSE_BIT;
 767       chunk_plus_offset(newp, psize)->head = FENCEPOST_HEAD;
 768       chunk_plus_offset(newp, psize+SIZE_T_SIZE)->head = 0;
 769       return newp;
 770     }
 771   }
 772   return NULL;
 773 }
 774
 775 /* -------------------------- mspace management -------------------------- */
 776
 777 /* Initialize top chunk and its size */
 778 static void init_top(mstate m, mchunkptr p, size_t psize)
 779 {
 780   /* Ensure alignment */
 781   size_t offset = align_offset(chunk2mem(p));
 782   p = (mchunkptr)((char *)p + offset);
 783   psize -= offset;
 784
 785   m->top = p;
 786   m->topsize = psize;
 787   p->head = psize | PINUSE_BIT;
 788   /* set size of fake trailing chunk holding overhead space only once */
 789   chunk_plus_offset(p, psize)->head = TOP_FOOT_SIZE;
 790   m->trim_check = DEFAULT_TRIM_THRESHOLD; /* reset on each update */
 791 }
 792
 793 /* Initialize bins for a new mstate that is otherwise zeroed out */
 794 static void init_bins(mstate m)
 795 {
 796   /* Establish circular links for smallbins */
 797   bindex_t i;
 798   for (i = 0; i < NSMALLBINS; i++) {
 799     sbinptr bin = smallbin_at(m,i);
 800     bin->fd = bin->bk = bin;
 801   }
 802 }
 803
 804 /* Allocate chunk and prepend remainder with chunk in successor base. */
 805 static void *prepend_alloc(mstate m, char *newbase, char *oldbase, size_t nb)
 806 {
 807   mchunkptr p = align_as_chunk(newbase);
 808   mchunkptr oldfirst = align_as_chunk(oldbase);
 809   size_t psize = (size_t)((char *)oldfirst - (char *)p);
 810   mchunkptr q = chunk_plus_offset(p, nb);
 811   size_t qsize = psize - nb;
 812   set_size_and_pinuse_of_inuse_chunk(m, p, nb);
 813
 814   /* consolidate remainder with first chunk of old base */
 815   if (oldfirst == m->top) {
 816     size_t tsize = m->topsize += qsize;
 817     m->top = q;
 818     q->head = tsize | PINUSE_BIT;
 819   } else if (oldfirst == m->dv) {
 820     size_t dsize = m->dvsize += qsize;
 821     m->dv = q;
 822     set_size_and_pinuse_of_free_chunk(q, dsize);
 823   } else {
 824     if (!cinuse(oldfirst)) {
 825       size_t nsize = chunksize(oldfirst);
 826       unlink_chunk(m, oldfirst, nsize);
 827       oldfirst = chunk_plus_offset(oldfirst, nsize);
 828       qsize += nsize;
 829     }
 830     set_free_with_pinuse(q, qsize, oldfirst);
 831     insert_chunk(m, q, qsize);
 832   }
 833
 834   return chunk2mem(p);
 835 }
 836
 837 /* Add a segment to hold a new noncontiguous region */
 838 static void add_segment(mstate m, char *tbase, size_t tsize)
 839 {
 840   /* Determine locations and sizes of segment, fenceposts, old top */
 841   char *old_top = (char *)m->top;
 842   msegmentptr oldsp = segment_holding(m, old_top);
 843   char *old_end = oldsp->base + oldsp->size;
 844   size_t ssize = pad_request(sizeof(struct malloc_segment));
 845   char *rawsp = old_end - (ssize + FOUR_SIZE_T_SIZES + CHUNK_ALIGN_MASK);
 846   size_t offset = align_offset(chunk2mem(rawsp));
 847   char *asp = rawsp + offset;
 848   char *csp = (asp < (old_top + MIN_CHUNK_SIZE))? old_top : asp;
 849   mchunkptr sp = (mchunkptr)csp;
 850   msegmentptr ss = (msegmentptr)(chunk2mem(sp));
 851   mchunkptr tnext = chunk_plus_offset(sp, ssize);
 852   mchunkptr p = tnext;
 853
 854   /* reset top to new space */
 855   init_top(m, (mchunkptr)tbase, tsize - TOP_FOOT_SIZE);
 856
 857   /* Set up segment record */
 858   set_size_and_pinuse_of_inuse_chunk(m, sp, ssize);
 859   *ss = m->seg; /* Push current record */
 860   m->seg.base = tbase;
 861   m->seg.size = tsize;
 862   m->seg.next = ss;
 863
 864   /* Insert trailing fenceposts */
 865   for (;;) {
 866     mchunkptr nextp = chunk_plus_offset(p, SIZE_T_SIZE);
 867     p->head = FENCEPOST_HEAD;
 868     if ((char *)(&(nextp->head)) < old_end)
 869       p = nextp;
 870     else
 871       break;
 872   }
 873
 874   /* Insert the rest of old top into a bin as an ordinary free chunk */
 875   if (csp != old_top) {
 876     mchunkptr q = (mchunkptr)old_top;
 877     size_t psize = (size_t)(csp - old_top);
 878     mchunkptr tn = chunk_plus_offset(q, psize);
 879     set_free_with_pinuse(q, psize, tn);
 880     insert_chunk(m, q, psize);
 881   }
 882 }
 883
 884 /* -------------------------- System allocation -------------------------- */
 885
 886 static void *alloc_sys(mstate m, size_t nb)
 887 {
 888   char *tbase = CMFAIL;
 889   size_t tsize = 0;
 890
 891   /* Directly map large chunks */
 892   if (LJ_UNLIKELY(nb >= DEFAULT_MMAP_THRESHOLD)) {
 893     void *mem = direct_alloc(nb);
 894     if (mem != 0)
 895       return mem;
 896   }
 897
 898   {
 899     size_t req = nb + TOP_FOOT_SIZE + SIZE_T_ONE;
 900     size_t rsize = granularity_align(req);
 901     if (LJ_LIKELY(rsize > nb)) { /* Fail if wraps around zero */
 902       char *mp = (char *)(CALL_MMAP(rsize));
 903       if (mp != CMFAIL) {
 904         tbase = mp;
 905         tsize = rsize;
 906       }
 907     }
 908   }
 909
 910   if (tbase != CMFAIL) {
 911     msegmentptr sp = &m->seg;
 912     /* Try to merge with an existing segment */
 913     while (sp != 0 && tbase != sp->base + sp->size)
 914       sp = sp->next;
 915     if (sp != 0 && segment_holds(sp, m->top)) { /* append */
 916       sp->size += tsize;
 917       init_top(m, m->top, m->topsize + tsize);
 918     } else {
 919       sp = &m->seg;
 920       while (sp != 0 && sp->base != tbase + tsize)
 921         sp = sp->next;
 922       if (sp != 0) {
 923         char *oldbase = sp->base;
 924         sp->base = tbase;
 925         sp->size += tsize;
 926         return prepend_alloc(m, tbase, oldbase, nb);
 927       } else {
 928         add_segment(m, tbase, tsize);
 929       }
 930     }
 931
 932     if (nb < m->topsize) { /* Allocate from new or extended top space */
 933       size_t rsize = m->topsize -= nb;
 934       mchunkptr p = m->top;
 935       mchunkptr r = m->top = chunk_plus_offset(p, nb);
 936       r->head = rsize | PINUSE_BIT;
 937       set_size_and_pinuse_of_inuse_chunk(m, p, nb);
 938       return chunk2mem(p);
 939     }
 940   }
 941
 942   return NULL;
 943 }
 944
 945 /* -----------------------  system deallocation -------------------------- */
 946
 947 /* Unmap and unlink any mmapped segments that don't contain used chunks */
 948 static size_t release_unused_segments(mstate m)
 949 {
 950   size_t released = 0;
 951   size_t nsegs = 0;
 952   msegmentptr pred = &m->seg;
 953   msegmentptr sp = pred->next;
 954   while (sp != 0) {
 955     char *base = sp->base;
 956     size_t size = sp->size;
 957     msegmentptr next = sp->next;
 958     nsegs++;
 959     {
 960       mchunkptr p = align_as_chunk(base);
 961       size_t psize = chunksize(p);
 962       /* Can unmap if first chunk holds entire segment and not pinned */
 963       if (!cinuse(p) && (char *)p + psize >= base + size - TOP_FOOT_SIZE) {
 964         tchunkptr tp = (tchunkptr)p;
 965         if (p == m->dv) {
 966           m->dv = 0;
 967           m->dvsize = 0;
 968         } else {
 969           unlink_large_chunk(m, tp);
 970         }
 971         if (CALL_MUNMAP(base, size) == 0) {
 972           released += size;
 973           /* unlink obsoleted record */
 974           sp = pred;
 975           sp->next = next;
 976         } else { /* back out if cannot unmap */
 977           insert_large_chunk(m, tp, psize);
 978         }
 979       }
 980     }
 981     pred = sp;
 982     sp = next;
 983   }
 984   /* Reset check counter */
 985   m->release_checks = nsegs > MAX_RELEASE_CHECK_RATE ?
 986                       nsegs : MAX_RELEASE_CHECK_RATE;
 987   return released;
 988 }
 989
 990 static int alloc_trim(mstate m, size_t pad)
 991 {
 992   size_t released = 0;
 993   if (pad < MAX_REQUEST && is_initialized(m)) {
 994     pad += TOP_FOOT_SIZE; /* ensure enough room for segment overhead */
 995
 996     if (m->topsize > pad) {
 997       /* Shrink top space in granularity-size units, keeping at least one */
 998       size_t unit = DEFAULT_GRANULARITY;
 999       size_t extra = ((m->topsize - pad + (unit - SIZE_T_ONE)) / unit -
1000                       SIZE_T_ONE) * unit;
1001       msegmentptr sp = segment_holding(m, (char *)m->top);
1002
1003       if (sp->size >= extra &&
1004           !has_segment_link(m, sp)) { /* can't shrink if pinned */
1005         size_t newsize = sp->size - extra;
1006         /* Prefer mremap, fall back to munmap */
1007         if ((CALL_MREMAP(sp->base, sp->size, newsize, CALL_MREMAP_NOMOVE) != MFAIL) ||
1008             (CALL_MUNMAP(sp->base + newsize, extra) == 0)) {
1009           released = extra;
1010         }
1011       }
1012
1013       if (released != 0) {
1014         sp->size -= released;
1015         init_top(m, m->top, m->topsize - released);
1016       }
1017     }
1018
1019     /* Unmap any unused mmapped segments */
1020     released += release_unused_segments(m);
1021
1022     /* On failure, disable autotrim to avoid repeated failed future calls */
1023     if (released == 0 && m->topsize > m->trim_check)
1024       m->trim_check = MAX_SIZE_T;
1025   }
1026
1027   return (released != 0)? 1 : 0;
1028 }
1029
1030 /* ---------------------------- malloc support --------------------------- */
1031
1032 /* allocate a large request from the best fitting chunk in a treebin */
1033 static void *tmalloc_large(mstate m, size_t nb)
1034 {
1035   tchunkptr v = 0;
1036   size_t rsize = ~nb+1; /* Unsigned negation */
1037   tchunkptr t;
1038   bindex_t idx;
1039   compute_tree_index(nb, idx);
1040
1041   if ((t = *treebin_at(m, idx)) != 0) {
1042     /* Traverse tree for this bin looking for node with size == nb */
1043     size_t sizebits = nb << leftshift_for_tree_index(idx);
1044     tchunkptr rst = 0;  /* The deepest untaken right subtree */
1045     for (;;) {
1046       tchunkptr rt;
1047       size_t trem = chunksize(t) - nb;
1048       if (trem < rsize) {
1049         v = t;
1050         if ((rsize = trem) == 0)
1051           break;
1052       }
1053       rt = t->child[1];
1054       t = t->child[(sizebits >> (SIZE_T_BITSIZE-SIZE_T_ONE)) & 1];
1055       if (rt != 0 && rt != t)
1056         rst = rt;
1057       if (t == 0) {
1058         t = rst; /* set t to least subtree holding sizes > nb */
1059         break;
1060       }
1061       sizebits <<= 1;
1062     }
1063   }
1064
1065   if (t == 0 && v == 0) { /* set t to root of next non-empty treebin */
1066     binmap_t leftbits = left_bits(idx2bit(idx)) & m->treemap;
1067     if (leftbits != 0)
1068       t = *treebin_at(m, lj_ffs(leftbits));
1069   }
1070
1071   while (t != 0) { /* find smallest of tree or subtree */
1072     size_t trem = chunksize(t) - nb;
1073     if (trem < rsize) {
1074       rsize = trem;
1075       v = t;
1076     }
1077     t = leftmost_child(t);
1078   }
1079
1080   /*  If dv is a better fit, return NULL so malloc will use it */
1081   if (v != 0 && rsize < (size_t)(m->dvsize - nb)) {
1082     mchunkptr r = chunk_plus_offset(v, nb);
1083     unlink_large_chunk(m, v);
1084     if (rsize < MIN_CHUNK_SIZE) {
1085       set_inuse_and_pinuse(m, v, (rsize + nb));
1086     } else {
1087       set_size_and_pinuse_of_inuse_chunk(m, v, nb);
1088       set_size_and_pinuse_of_free_chunk(r, rsize);
1089       insert_chunk(m, r, rsize);
1090     }
1091     return chunk2mem(v);
1092   }
1093   return NULL;
1094 }
1095
1096 /* allocate a small request from the best fitting chunk in a treebin */
1097 static void *tmalloc_small(mstate m, size_t nb)
1098 {
1099   tchunkptr t, v;
1100   mchunkptr r;
1101   size_t rsize;
1102   bindex_t i = lj_ffs(m->treemap);
1103
1104   v = t = *treebin_at(m, i);
1105   rsize = chunksize(t) - nb;
1106
1107   while ((t = leftmost_child(t)) != 0) {
1108     size_t trem = chunksize(t) - nb;
1109     if (trem < rsize) {
1110       rsize = trem;
1111       v = t;
1112     }
1113   }
1114
1115   r = chunk_plus_offset(v, nb);
1116   unlink_large_chunk(m, v);
1117   if (rsize < MIN_CHUNK_SIZE) {
1118     set_inuse_and_pinuse(m, v, (rsize + nb));
1119   } else {
1120     set_size_and_pinuse_of_inuse_chunk(m, v, nb);
1121     set_size_and_pinuse_of_free_chunk(r, rsize);
1122     replace_dv(m, r, rsize);
1123   }
1124   return chunk2mem(v);
1125 }
1126
1127 /* ----------------------------------------------------------------------- */
1128
1129 void *lj_alloc_create(void)
1130 {
1131   size_t tsize = DEFAULT_GRANULARITY;
1132   char *tbase;
1133   INIT_MMAP();
1134   tbase = (char *)(CALL_MMAP(tsize));
1135   if (tbase != CMFAIL) {
1136     size_t msize = pad_request(sizeof(struct malloc_state));
1137     mchunkptr mn;
1138     mchunkptr msp = align_as_chunk(tbase);
1139     mstate m = (mstate)(chunk2mem(msp));
1140     memset(m, 0, msize);
1141     msp->head = (msize|PINUSE_BIT|CINUSE_BIT);
1142     m->seg.base = tbase;
1143     m->seg.size = tsize;
1144     m->release_checks = MAX_RELEASE_CHECK_RATE;
1145     init_bins(m);
1146     mn = next_chunk(mem2chunk(m));
1147     init_top(m, mn, (size_t)((tbase + tsize) - (char *)mn) - TOP_FOOT_SIZE);
1148     return m;
1149   }
1150   return NULL;
1151 }
1152
1153 void lj_alloc_destroy(void *msp)
1154 {
1155   mstate ms = (mstate)msp;
1156   msegmentptr sp = &ms->seg;
1157   while (sp != 0) {
1158     char *base = sp->base;
1159     size_t size = sp->size;
1160     sp = sp->next;
1161     CALL_MUNMAP(base, size);
1162   }
1163 }
1164
1165 static LJ_NOINLINE void *lj_alloc_malloc(void *msp, size_t nsize)
1166 {
1167   mstate ms = (mstate)msp;
1168   void *mem;
1169   size_t nb;
1170   if (nsize <= MAX_SMALL_REQUEST) {
1171     bindex_t idx;
1172     binmap_t smallbits;
1173     nb = (nsize < MIN_REQUEST)? MIN_CHUNK_SIZE : pad_request(nsize);
1174     idx = small_index(nb);
1175     smallbits = ms->smallmap >> idx;
1176
1177     if ((smallbits & 0x3U) != 0) { /* Remainderless fit to a smallbin. */
1178       mchunkptr b, p;
1179       idx += ~smallbits & 1;       /* Uses next bin if idx empty */
1180       b = smallbin_at(ms, idx);
1181       p = b->fd;
1182       unlink_first_small_chunk(ms, b, p, idx);
1183       set_inuse_and_pinuse(ms, p, small_index2size(idx));
1184       mem = chunk2mem(p);
1185       return mem;
1186     } else if (nb > ms->dvsize) {
1187       if (smallbits != 0) { /* Use chunk in next nonempty smallbin */
1188         mchunkptr b, p, r;
1189         size_t rsize;
1190         binmap_t leftbits = (smallbits << idx) & left_bits(idx2bit(idx));
1191         bindex_t i = lj_ffs(leftbits);
1192         b = smallbin_at(ms, i);
1193         p = b->fd;
1194         unlink_first_small_chunk(ms, b, p, i);
1195         rsize = small_index2size(i) - nb;
1196         /* Fit here cannot be remainderless if 4byte sizes */
1197         if (SIZE_T_SIZE != 4 && rsize < MIN_CHUNK_SIZE) {
1198           set_inuse_and_pinuse(ms, p, small_index2size(i));
1199         } else {
1200           set_size_and_pinuse_of_inuse_chunk(ms, p, nb);
1201           r = chunk_plus_offset(p, nb);
1202           set_size_and_pinuse_of_free_chunk(r, rsize);
1203           replace_dv(ms, r, rsize);
1204         }
1205         mem = chunk2mem(p);
1206         return mem;
1207       } else if (ms->treemap != 0 && (mem = tmalloc_small(ms, nb)) != 0) {
1208         return mem;
1209       }
1210     }
1211   } else if (nsize >= MAX_REQUEST) {
1212     nb = MAX_SIZE_T; /* Too big to allocate. Force failure (in sys alloc) */
1213   } else {
1214     nb = pad_request(nsize);
1215     if (ms->treemap != 0 && (mem = tmalloc_large(ms, nb)) != 0) {
1216       return mem;
1217     }
1218   }
1219
1220   if (nb <= ms->dvsize) {
1221     size_t rsize = ms->dvsize - nb;
1222     mchunkptr p = ms->dv;
1223     if (rsize >= MIN_CHUNK_SIZE) { /* split dv */
1224       mchunkptr r = ms->dv = chunk_plus_offset(p, nb);
1225       ms->dvsize = rsize;
1226       set_size_and_pinuse_of_free_chunk(r, rsize);
1227       set_size_and_pinuse_of_inuse_chunk(ms, p, nb);
1228     } else { /* exhaust dv */
1229       size_t dvs = ms->dvsize;
1230       ms->dvsize = 0;
1231       ms->dv = 0;
1232       set_inuse_and_pinuse(ms, p, dvs);
1233     }
1234     mem = chunk2mem(p);
1235     return mem;
1236   } else if (nb < ms->topsize) { /* Split top */
1237     size_t rsize = ms->topsize -= nb;
1238     mchunkptr p = ms->top;
1239     mchunkptr r = ms->top = chunk_plus_offset(p, nb);
1240     r->head = rsize | PINUSE_BIT;
1241     set_size_and_pinuse_of_inuse_chunk(ms, p, nb);
1242     mem = chunk2mem(p);
1243     return mem;
1244   }
1245   return alloc_sys(ms, nb);
1246 }
1247
1248 static LJ_NOINLINE void *lj_alloc_free(void *msp, void *ptr)
1249 {
1250   if (ptr != 0) {
1251     mchunkptr p = mem2chunk(ptr);
1252     mstate fm = (mstate)msp;
1253     size_t psize = chunksize(p);
1254     mchunkptr next = chunk_plus_offset(p, psize);
1255     if (!pinuse(p)) {
1256       size_t prevsize = p->prev_foot;
1257       if ((prevsize & IS_DIRECT_BIT) != 0) {
1258         prevsize &= ~IS_DIRECT_BIT;
1259         psize += prevsize + DIRECT_FOOT_PAD;
1260         CALL_MUNMAP((char *)p - prevsize, psize);
1261         return NULL;
1262       } else {
1263         mchunkptr prev = chunk_minus_offset(p, prevsize);
1264         psize += prevsize;
1265         p = prev;
1266         /* consolidate backward */
1267         if (p != fm->dv) {
1268           unlink_chunk(fm, p, prevsize);
1269         } else if ((next->head & INUSE_BITS) == INUSE_BITS) {
1270           fm->dvsize = psize;
1271           set_free_with_pinuse(p, psize, next);
1272           return NULL;
1273         }
1274       }
1275     }
1276     if (!cinuse(next)) {  /* consolidate forward */
1277       if (next == fm->top) {
1278         size_t tsize = fm->topsize += psize;
1279         fm->top = p;
1280         p->head = tsize | PINUSE_BIT;
1281         if (p == fm->dv) {
1282           fm->dv = 0;
1283           fm->dvsize = 0;
1284         }
1285         if (tsize > fm->trim_check)
1286           alloc_trim(fm, 0);
1287         return NULL;
1288       } else if (next == fm->dv) {
1289         size_t dsize = fm->dvsize += psize;
1290         fm->dv = p;
1291         set_size_and_pinuse_of_free_chunk(p, dsize);
1292         return NULL;
1293       } else {
1294         size_t nsize = chunksize(next);
1295         psize += nsize;
1296         unlink_chunk(fm, next, nsize);
1297         set_size_and_pinuse_of_free_chunk(p, psize);
1298         if (p == fm->dv) {
1299           fm->dvsize = psize;
1300           return NULL;
1301         }
1302       }
1303     } else {
1304       set_free_with_pinuse(p, psize, next);
1305     }
1306
1307     if (is_small(psize)) {
1308       insert_small_chunk(fm, p, psize);
1309     } else {
1310       tchunkptr tp = (tchunkptr)p;
1311       insert_large_chunk(fm, tp, psize);
1312       if (--fm->release_checks == 0)
1313         release_unused_segments(fm);
1314     }
1315   }
1316   return NULL;
1317 }
1318
1319 static LJ_NOINLINE void *lj_alloc_realloc(void *msp, void *ptr, size_t nsize)
1320 {
1321   if (nsize >= MAX_REQUEST) {
1322     return NULL;
1323   } else {
1324     mstate m = (mstate)msp;
1325     mchunkptr oldp = mem2chunk(ptr);
1326     size_t oldsize = chunksize(oldp);
1327     mchunkptr next = chunk_plus_offset(oldp, oldsize);
1328     mchunkptr newp = 0;
1329     size_t nb = request2size(nsize);
1330
1331     /* Try to either shrink or extend into top. Else malloc-copy-free */
1332     if (is_direct(oldp)) {
1333       newp = direct_resize(oldp, nb);  /* this may return NULL. */
1334     } else if (oldsize >= nb) { /* already big enough */
1335       size_t rsize = oldsize - nb;
1336       newp = oldp;
1337       if (rsize >= MIN_CHUNK_SIZE) {
1338         mchunkptr rem = chunk_plus_offset(newp, nb);
1339         set_inuse(m, newp, nb);
1340         set_inuse(m, rem, rsize);
1341         lj_alloc_free(m, chunk2mem(rem));
1342       }
1343     } else if (next == m->top && oldsize + m->topsize > nb) {
1344       /* Expand into top */
1345       size_t newsize = oldsize + m->topsize;
1346       size_t newtopsize = newsize - nb;
1347       mchunkptr newtop = chunk_plus_offset(oldp, nb);
1348       set_inuse(m, oldp, nb);
1349       newtop->head = newtopsize |PINUSE_BIT;
1350       m->top = newtop;
1351       m->topsize = newtopsize;
1352       newp = oldp;
1353     }
1354
1355     if (newp != 0) {
1356       return chunk2mem(newp);
1357     } else {
1358       void *newmem = lj_alloc_malloc(m, nsize);
1359       if (newmem != 0) {
1360         size_t oc = oldsize - overhead_for(oldp);
1361         memcpy(newmem, ptr, oc < nsize ? oc : nsize);
1362         lj_alloc_free(m, ptr);
1363       }
1364       return newmem;
1365     }
1366   }
1367 }
1368
1369 void *lj_alloc_f(void *msp, void *ptr, size_t osize, size_t nsize)
1370 {
1371   (void)osize;
1372   if (nsize == 0) {
1373     return lj_alloc_free(msp, ptr);
1374   } else if (ptr == NULL) {
1375     return lj_alloc_malloc(msp, nsize);
1376   } else {
1377     return lj_alloc_realloc(msp, ptr, nsize);
1378   }
1379 }
1380
1381 #endif