cosmopolitan/third_party/dlmalloc/init.inc

/* ---------------------------- setting mparams -------------------------- */

#if LOCK_AT_FORK
static void dlmalloc_pre_fork(void)         { ACQUIRE_LOCK(&(gm)->mutex); }
static void dlmalloc_post_fork_parent(void) { RELEASE_LOCK(&(gm)->mutex); }
static void dlmalloc_post_fork_child(void)  { (void)INITIAL_LOCK(&(gm)->mutex); }
#endif /* LOCK_AT_FORK */

/* Initialize mparams */
__attribute__((__constructor__(50))) int init_mparams(void) {
#ifdef NEED_GLOBAL_LOCK_INIT
  if (malloc_global_mutex_status <= 0)
    init_malloc_global_mutex();
#endif

  // ACQUIRE_MALLOC_GLOBAL_LOCK();
  if (mparams.magic == 0) {
    size_t magic;
    size_t psize;
    size_t gsize;

#if defined(__COSMOPOLITAN__)
    psize = FRAMESIZE;
    gsize = FRAMESIZE;
#elif !defined(WIN32)
    psize = malloc_getpagesize;
    gsize = ((DEFAULT_GRANULARITY != 0)? DEFAULT_GRANULARITY : psize);
#else /* WIN32 */
    {
      SYSTEM_INFO system_info;
      GetSystemInfo(&system_info);
      psize = system_info.dwPageSize;
      gsize = ((DEFAULT_GRANULARITY != 0)?
               DEFAULT_GRANULARITY : system_info.dwAllocationGranularity);
    }
#endif /* WIN32 */

    /* Sanity-check configuration:
       size_t must be unsigned and as wide as pointer type.
       ints must be at least 4 bytes.
       alignment must be at least 8.
       Alignment, min chunk size, and page size must all be powers of 2.
    */
    if ((sizeof(size_t) != sizeof(char*)) ||
        (MAX_SIZE_T < MIN_CHUNK_SIZE)  ||
        (sizeof(int) < 4)  ||
        (MALLOC_ALIGNMENT < (size_t)8U) ||
        ((MALLOC_ALIGNMENT & (MALLOC_ALIGNMENT-SIZE_T_ONE)) != 0) ||
        ((MCHUNK_SIZE      & (MCHUNK_SIZE-SIZE_T_ONE))      != 0) ||
        ((gsize            & (gsize-SIZE_T_ONE))            != 0) ||
        ((psize            & (psize-SIZE_T_ONE))            != 0))
      ABORT;
    mparams.granularity = gsize;
    mparams.page_size = psize;
    mparams.mmap_threshold = DEFAULT_MMAP_THRESHOLD;
    mparams.trim_threshold = DEFAULT_TRIM_THRESHOLD;
#if MORECORE_CONTIGUOUS
    mparams.default_mflags = USE_LOCK_BIT|USE_MMAP_BIT;
#else  /* MORECORE_CONTIGUOUS */
    mparams.default_mflags = USE_LOCK_BIT|USE_MMAP_BIT|USE_NONCONTIGUOUS_BIT;
#endif /* MORECORE_CONTIGUOUS */

#if !ONLY_MSPACES
    /* Set up lock for main malloc area */
    gm->mflags = mparams.default_mflags;
    (void)INITIAL_LOCK(&gm->mutex);
#endif

#if LOCK_AT_FORK
    pthread_atfork(&dlmalloc_pre_fork,
                   &dlmalloc_post_fork_parent,
                   &dlmalloc_post_fork_child);
#endif

    {
#if USE_DEV_RANDOM
      int fd;
      unsigned char buf[sizeof(size_t)];
      /* Try to use /dev/urandom, else fall back on using time */
      if ((fd = open("/dev/urandom", O_RDONLY)) >= 0 &&
          read(fd, buf, sizeof(buf)) == sizeof(buf)) {
        magic = *((size_t *) buf);
        close(fd);
      }
      else
#endif /* USE_DEV_RANDOM */
      magic = (size_t)(_rand64() ^ (size_t)0x55555555U);
      magic |= (size_t)8U;    /* ensure nonzero */
      magic &= ~(size_t)7U;   /* improve chances of fault for bad values */
      /* Until memory modes commonly available, use volatile-write */
      (*(volatile size_t *)(&(mparams.magic))) = magic;
    }
  }

  // RELEASE_MALLOC_GLOBAL_LOCK();

  __runlevel = RUNLEVEL_MALLOC;
  return 1;
}

/* support for mallopt */
static int change_mparam(int param_number, int value) {
  size_t val;
  ensure_initialization();
  val = (value == -1)? MAX_SIZE_T : (size_t)value;
  switch(param_number) {
  case M_TRIM_THRESHOLD:
    mparams.trim_threshold = val;
    return 1;
  case M_GRANULARITY:
    if (val >= mparams.page_size && ((val & (val-1)) == 0)) {
      mparams.granularity = val;
      return 1;
    }
    else
      return 0;
  case M_MMAP_THRESHOLD:
    mparams.mmap_threshold = val;
    return 1;
  default:
    return 0;
  }
}