malloc.c

linux下bash的源码

#endif /* BSD4_2 */
}

static void
getpool ()
{
  register int nu;
  register char *cp = sbrk (0);

  if ((int) cp & 0x3ff)	/* land on 1K boundaries */
    sbrk (1024 - ((int) cp & 0x3ff));

  /* Record address of start of space allocated by malloc.  */
  if (_malloc_base == 0)
    _malloc_base = cp;

  /* Get 2k of storage */

  cp = sbrk (04000);
  if (cp == (char *) -1)
    return;

  /* Divide it into an initial 8-word block
     plus one block of size 2**nu for nu = 3 ... 10.  */

  CHAIN (cp) = nextf[0];
  nextf[0] = (struct mhead *) cp;
  ((struct mhead *) cp) -> mh_alloc = ISFREE;
  ((struct mhead *) cp) -> mh_index = 0;
  cp += 8;

  for (nu = 0; nu < 7; nu++)
    {
      CHAIN (cp) = nextf[nu];
      nextf[nu] = (struct mhead *) cp;
      ((struct mhead *) cp) -> mh_alloc = ISFREE;
      ((struct mhead *) cp) -> mh_index = nu;
      cp += 8 << nu;
    }
}

char *
malloc (n)		/* get a block */
     unsigned n;
{
  register struct mhead *p;
  register unsigned int nbytes;
  register int nunits = 0;

  /* Figure out how many bytes are required, rounding up to the nearest
     multiple of 4, then figure out which nextf[] area to use */
  nbytes = (n + sizeof *p + EXTRA + 3) & ~3;
  {
    register unsigned int   shiftr = (nbytes - 1) >> 2;

    while (shiftr >>= 1)
      nunits++;
  }

  /* In case this is reentrant use of malloc from signal handler,
     pick a block size that no other malloc level is currently
     trying to allocate.  That's the easiest harmless way not to
     interfere with the other level of execution.  */
  while (busy[nunits]) nunits++;
  busy[nunits] = 1;

  /* If there are no blocks of the appropriate size, go get some */
  /* COULD SPLIT UP A LARGER BLOCK HERE ... ACT */
  if (nextf[nunits] == 0)
    morecore (nunits);

  /* Get one block off the list, and set the new list head */
  if ((p = nextf[nunits]) == 0)
    {
      busy[nunits] = 0;
      return 0;
    }
  nextf[nunits] = CHAIN (p);
  busy[nunits] = 0;

  /* Check for free block clobbered */
  /* If not for this check, we would gobble a clobbered free chain ptr */
  /* and bomb out on the NEXT allocate of this size block */
  if (p -> mh_alloc != ISFREE || p -> mh_index != nunits)
#ifdef rcheck
    botch ("block on free list clobbered");
#else /* not rcheck */
    abort ();
#endif /* not rcheck */

  /* Fill in the info, and if range checking, set up the magic numbers */
  p -> mh_alloc = ISALLOC;
#ifdef rcheck
  p -> mh_nbytes = n;
  p -> mh_magic4 = MAGIC4;
  {
    register char  *m = (char *) (p + 1) + n;

    *m++ = MAGIC1, *m++ = MAGIC1, *m++ = MAGIC1, *m = MAGIC1;
  }
#else /* not rcheck */
  p -> mh_size = n;
#endif /* not rcheck */
#ifdef MSTATS
  nmalloc[nunits]++;
  nmal++;
#endif /* MSTATS */
  return (char *) (p + 1);
}

void
free (mem)
     char *mem;
{
  register struct mhead *p;
  {
    register char *ap = mem;

    if (ap == 0)
      return;

    p = (struct mhead *) ap - 1;

    if (p -> mh_alloc == ISMEMALIGN)
      {
#ifdef rcheck
	ap -= p->mh_nbytes;
#endif
	p = (struct mhead *) ap - 1;
      }

#ifndef rcheck
    if (p -> mh_alloc != ISALLOC)
      abort ();

#else /* rcheck */
    if (p -> mh_alloc != ISALLOC)
      {
	if (p -> mh_alloc == ISFREE)
	  botch ("free: Called with already freed block argument\n");
	else
	  botch ("free: Called with bad argument\n");
      }

    ASSERT (p -> mh_magic4 == MAGIC4);
    ap += p -> mh_nbytes;
    ASSERT (*ap++ == MAGIC1); ASSERT (*ap++ == MAGIC1);
    ASSERT (*ap++ == MAGIC1); ASSERT (*ap   == MAGIC1);
#endif /* rcheck */
  }
  {
    register int nunits = p -> mh_index;

    ASSERT (nunits <= 29);
    p -> mh_alloc = ISFREE;

    /* Protect against signal handlers calling malloc.  */
    busy[nunits] = 1;
    /* Put this block on the free list.  */
    CHAIN (p) = nextf[nunits];
    nextf[nunits] = p;
    busy[nunits] = 0;

#ifdef MSTATS
    nmalloc[nunits]--;
    nfre++;
#endif /* MSTATS */
  }
}

char *
realloc (mem, n)
     char *mem;
     register unsigned n;
{
  register struct mhead *p;
  register unsigned int tocopy;
  register unsigned int nbytes;
  register int nunits;

  if ((p = (struct mhead *) mem) == 0)
    return malloc (n);
  p--;
  nunits = p -> mh_index;
  ASSERT (p -> mh_alloc == ISALLOC);
#ifdef rcheck
  ASSERT (p -> mh_magic4 == MAGIC4);
  {
    register char *m = mem + (tocopy = p -> mh_nbytes);
    ASSERT (*m++ == MAGIC1); ASSERT (*m++ == MAGIC1);
    ASSERT (*m++ == MAGIC1); ASSERT (*m   == MAGIC1);
  }
#else /* not rcheck */
  if (p -> mh_index >= 13)
    tocopy = (1 << (p -> mh_index + 3)) - sizeof *p;
  else
    tocopy = p -> mh_size;
#endif /* not rcheck */

  /* See if desired size rounds to same power of 2 as actual size. */
  nbytes = (n + sizeof *p + EXTRA + 7) & ~7;

  /* If ok, use the same block, just marking its size as changed.  */
  if (nbytes > (4 << nunits) && nbytes <= (8 << nunits))
    {
#ifdef rcheck
      register char *m = mem + tocopy;
      *m++ = 0;  *m++ = 0;  *m++ = 0;  *m++ = 0;
      p-> mh_nbytes = n;
      m = mem + n;
      *m++ = MAGIC1;  *m++ = MAGIC1;  *m++ = MAGIC1;  *m++ = MAGIC1;
#else /* not rcheck */
      p -> mh_size = n;
#endif /* not rcheck */
      return mem;
    }

  if (n < tocopy)
    tocopy = n;
  {
    register char *new;

    if ((new = malloc (n)) == 0)
      return 0;
    bcopy (mem, new, tocopy);
    free (mem);
    return new;
  }
}

char *
memalign (alignment, size)
     unsigned alignment, size;
{
  register char *ptr = malloc (size + alignment);
  register char *aligned;
  register struct mhead *p;

  if (ptr == 0)
    return 0;
  /* If entire block has the desired alignment, just accept it.  */
  if (((int) ptr & (alignment - 1)) == 0)
    return ptr;
  /* Otherwise, get address of byte in the block that has that alignment.  */
  aligned = (char *) (((int) ptr + alignment - 1) & -alignment);

  /* Store a suitable indication of how to free the block,
     so that free can find the true beginning of it.  */
  p = (struct mhead *) aligned - 1;
  p -> mh_size = aligned - ptr;
  p -> mh_alloc = ISMEMALIGN;
  return aligned;
}

#if !defined (HPUX) && !defined (Multimax) && !defined (Multimax32k)
/* This runs into trouble with getpagesize on HPUX, and Multimax machines.
   Patching out seems cleaner than the ugly fix needed.  */
char *
valloc (size)
{
  return memalign (getpagesize (), size);
}
#endif /* !HPUX && !Multimax && !Multimax32k */

#ifdef MSTATS
/* Return statistics describing allocation of blocks of size 2**n. */

struct mstats_value
  {
    int blocksize;
    int nfree;
    int nused;
  };

struct mstats_value
malloc_stats (size)
     int size;
{
  struct mstats_value v;
  register int i;
  register struct mhead *p;

  v.nfree = 0;

  if (size < 0 || size >= 30)
    {
      v.blocksize = 0;
      v.nused = 0;
      return v;
    }

  v.blocksize = 1 << (size + 3);
  v.nused = nmalloc[size];

  for (p = nextf[size]; p; p = CHAIN (p))
    v.nfree++;

  return v;
}
#endif /* MSTATS */

/*
 *	This function returns the total number of bytes that the process
 *	will be allowed to allocate via the sbrk(2) system call.  On
 *	BSD systems this is the total space allocatable to stack and
 *	data.  On USG systems this is the data space only.
 */

#if !defined (HAVE_RESOURCE)
extern long ulimit ();

static void
get_lim_data ()
{    
  lim_data = ulimit (3, 0);
  lim_data -= (long) data_space_start;
}

#else /* HAVE_RESOURCE */
static void
get_lim_data ()
{
  struct rlimit XXrlimit;

  getrlimit (RLIMIT_DATA, &XXrlimit);
#ifdef RLIM_INFINITY
  lim_data = XXrlimit.rlim_cur & RLIM_INFINITY; /* soft limit */
#else
  lim_data = XXrlimit.rlim_cur;	/* soft limit */
#endif
}

#endif /* HAVE_RESOURCE */