guile/libguile/gc-card.c

/* Copyright (C) 1995,1996,1997,1998,1999,2000,2001, 2002, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 3 of
 * the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <assert.h>
#include <stdio.h>
#include <count-one-bits.h>

#include <gmp.h>

#include "libguile/_scm.h"
#include "libguile/async.h"
#include "libguile/deprecation.h"
#include "libguile/eval.h"
#include "libguile/gc.h"
#include "libguile/hashtab.h"
#include "libguile/numbers.h"
#include "libguile/ports.h"
#include "libguile/private-gc.h"
#include "libguile/root.h"
#include "libguile/smob.h"
#include "libguile/srfi-4.h"
#include "libguile/stackchk.h"
#include "libguile/stime.h"
#include "libguile/strings.h"
#include "libguile/struct.h"
#include "libguile/tags.h"
#include "libguile/unif.h"
#include "libguile/validate.h"
#include "libguile/vectors.h"
#include "libguile/weaks.h"

#include "libguile/private-gc.h"

long int scm_i_deprecated_memory_return;


/* During collection, this accumulates structures which are to be freed.
 */
SCM scm_i_structs_to_free;

/*
  Init all the free cells in CARD, prepending to *FREE_LIST.

  Return: FREE_COUNT, the number of cells collected.  This is
  typically the length of the *FREE_LIST, but for some special cases,
  we do not actually free the cell. To make the numbers match up, we
  do increase the FREE_COUNT.

  It would be cleaner to have a separate function sweep_value (), but
  that is too slow (functions with switch statements can't be
  inlined).

  NOTE:

  For many types of cells, allocation and a de-allocation involves
  calling malloc () and free ().  This is costly for small objects (due
  to malloc/free overhead.)  (should measure this).

  It might also be bad for threads: if several threads are allocating
  strings concurrently, then mallocs for both threads may have to
  fiddle with locks.

  It might be interesting to add a separate memory pool for small
  objects to each freelist.

  --hwn.
 */
int
scm_i_sweep_card (scm_t_cell *card, SCM *free_list, scm_t_heap_segment *seg)
#define FUNC_NAME "sweep_card"
{
  scm_t_c_bvec_long *bitvec = SCM_GC_CARD_BVEC (card);
  scm_t_cell *end = card + SCM_GC_CARD_N_CELLS;
  scm_t_cell *p = card;
  int span = seg->span;
  int offset = SCM_MAX (SCM_GC_CARD_N_HEADER_CELLS, span);
  int free_count = 0;
  
  /*
    I tried something fancy with shifting by one bit every word from
    the bitvec in turn, but it wasn't any faster, but quite a bit
    hairier.
   */
  for (p += offset; p < end; p += span, offset += span)
    {
      SCM scmptr = PTR2SCM (p);
      if (SCM_C_BVEC_GET (bitvec, offset))
        continue;
      free_count++;
      switch (SCM_TYP7 (scmptr))
	{
	case scm_tcs_struct:
	  /* The card can be swept more than once.  Check that it's
	   * the first time!
	   */
	  if (!SCM_STRUCT_GC_CHAIN (scmptr))
	    {
	      /* Structs need to be freed in a special order.
	       * This is handled by GC C hooks in struct.c.
	       */
	      SCM_SET_STRUCT_GC_CHAIN (scmptr, scm_i_structs_to_free);
	      scm_i_structs_to_free = scmptr;
	    }
	  continue;
      
	case scm_tcs_cons_imcar:
	case scm_tcs_cons_nimcar:
	case scm_tcs_closures:
	case scm_tc7_pws:
	  break;
	case scm_tc7_wvect:
	case scm_tc7_vector:
	  scm_i_vector_free (scmptr);
	  break;

	case scm_tc7_number:
	  switch SCM_TYP16 (scmptr)
            {
            case scm_tc16_real:
              break;
            case scm_tc16_big:
              mpz_clear (SCM_I_BIG_MPZ (scmptr));
              /* nothing else to do here since the mpz is in a double cell */
              break;
	    case scm_tc16_complex:
	      scm_gc_free (SCM_COMPLEX_MEM (scmptr), sizeof (scm_t_complex),
			   "complex");
	      break;
	    case scm_tc16_fraction:
	      /* nothing to do here since the num/denum of a fraction
		 are proper SCM objects themselves. */
	      break;
            }
          break;
	case scm_tc7_string:
	  scm_i_string_free (scmptr);
	  break;
	case scm_tc7_stringbuf:
	  scm_i_stringbuf_free (scmptr);
	  break;
	case scm_tc7_symbol:
	  scm_i_symbol_free (scmptr); 
	  break;
	case scm_tc7_variable:
	  break;
	case scm_tcs_subrs:
	  /* the various "subrs" (primitives) are never freed */
	  continue;
	case scm_tc7_port:
	  if SCM_OPENP (scmptr)
	    {
	      int k = SCM_PTOBNUM (scmptr);
	      size_t mm;
#if (SCM_DEBUG_CELL_ACCESSES == 1)
	      if (!(k < scm_numptob))
		{
		  fprintf (stderr, "undefined port type");
		  abort ();
		}
#endif
	      /* Keep "revealed" ports alive.  */
	      if (scm_revealed_count (scmptr) > 0)
		continue;
	      
	      /* Yes, I really do mean scm_ptobs[k].free */
	      /* rather than ftobs[k].close.  .close */
	      /* is for explicit CLOSE-PORT by user */
	      mm = scm_ptobs[k].free (scmptr);

	      if (mm != 0)
		{
#if SCM_ENABLE_DEPRECATED == 1
		  scm_c_issue_deprecation_warning
		    ("Returning non-0 from a port free function is "
		     "deprecated.  Use scm_gc_free et al instead.");
		  scm_c_issue_deprecation_warning_fmt
		    ("(You just returned non-0 while freeing a %s.)",
		     SCM_PTOBNAME (k));
		  scm_i_deprecated_memory_return += mm;
#else
		  abort ();
#endif
		}

	      SCM_SETSTREAM (scmptr, 0);
	      scm_i_remove_port (scmptr);
	      SCM_CLR_PORT_OPEN_FLAG (scmptr);
	    }
	  break;
	case scm_tc7_smob:
	  switch SCM_TYP16 (scmptr)
	    {
	    case scm_tc_free_cell:
	      break;
	    default:
	      {
		int k;
		k = SCM_SMOBNUM (scmptr);
#if (SCM_DEBUG_CELL_ACCESSES == 1)
		if (!(k < scm_numsmob))
		  {
		    fprintf (stderr, "undefined smob type");
		    abort ();
		  }
#endif
		if (scm_smobs[k].free)
		  {
		    size_t mm;
		    mm = scm_smobs[k].free (scmptr);
		    if (mm != 0)
		      {
#if SCM_ENABLE_DEPRECATED == 1
			scm_c_issue_deprecation_warning
			  ("Returning non-0 from a smob free function is "
			   "deprecated.  Use scm_gc_free et al instead.");
			scm_c_issue_deprecation_warning_fmt
			  ("(You just returned non-0 while freeing a %s.)",
			   SCM_SMOBNAME (k));
			scm_i_deprecated_memory_return += mm;
#else
			abort ();
#endif
		      }
		  }
		break;
	      }
	    }
	  break;
	default:
	  fprintf (stderr, "unknown type");
	  abort ();
	}

      SCM_GC_SET_CELL_WORD (scmptr, 0, scm_tc_free_cell);	  
      SCM_SET_FREE_CELL_CDR (scmptr, PTR2SCM (*free_list));
      *free_list = scmptr;
    }
  
  return free_count;
}
#undef FUNC_NAME


/*
  Like sweep, but no complicated logic to do the sweeping.
 */
int
scm_i_init_card_freelist (scm_t_cell *card, SCM *free_list,
			  scm_t_heap_segment *seg)
{
  int span = seg->span;
  scm_t_cell *end = card + SCM_GC_CARD_N_CELLS;
  scm_t_cell *p = end - span;
  int collected = 0;
  scm_t_c_bvec_long *bvec_ptr = (scm_t_c_bvec_long*) seg->bounds[1];
  int idx = (card  - seg->bounds[0]) / SCM_GC_CARD_N_CELLS; 

  bvec_ptr += idx * SCM_GC_CARD_BVEC_SIZE_IN_LONGS;
  SCM_GC_SET_CELL_BVEC (card, bvec_ptr);
  
  /*
     ASSUMPTION: n_header_cells <= 2. 
   */
  for (; p > card;  p -= span)
    {
      const SCM scmptr = PTR2SCM (p);
      SCM_GC_SET_CELL_WORD (scmptr, 0, scm_tc_free_cell);
      SCM_SET_FREE_CELL_CDR (scmptr, PTR2SCM (*free_list));
      *free_list = scmptr;
      collected ++;
    }

  return collected;
}

/*
  Amount of cells marked in this cell, measured in 1-cells.
 */
int
scm_i_card_marked_count (scm_t_cell *card, int span)
{
  scm_t_c_bvec_long* bvec = SCM_GC_CARD_BVEC (card);
  scm_t_c_bvec_long* bvec_end = (bvec + SCM_GC_CARD_BVEC_SIZE_IN_LONGS);
  
  int count = 0;
  while (bvec < bvec_end)
    {
      count += count_one_bits_l (*bvec);
      bvec ++;
    }
  return count * span;
}

void
scm_i_card_statistics (scm_t_cell *p, SCM hashtab, scm_t_heap_segment *seg)
{
  scm_t_c_bvec_long *bitvec = SCM_GC_CARD_BVEC (p);
  scm_t_cell * end = p + SCM_GC_CARD_N_CELLS;
  int span = seg->span;
  int offset = SCM_MAX (SCM_GC_CARD_N_HEADER_CELLS, span);

  if (!bitvec)
    /* Card P hasn't been initialized yet by `scm_i_init_card_freelist ()'. */
    return;

  for (p += offset; p < end; p += span, offset += span)
    {
      scm_t_bits tag = -1;
      SCM scmptr = PTR2SCM (p);

      if (!SCM_C_BVEC_GET (bitvec, offset))
        continue;

      tag = SCM_TYP7 (scmptr);
      if (tag == scm_tc7_smob || tag == scm_tc7_number)
	{
          /* Record smobs and numbers under 16 bits of the tag, so the
             different smob objects are distinguished, and likewise the
             different numbers big, real, complex and fraction. */
	  tag = SCM_TYP16(scmptr);
	}
      else
	switch (tag) 
	{
	case scm_tcs_cons_imcar:
	  tag = scm_tc2_int;
	  break;
	case scm_tcs_cons_nimcar:
	  tag = scm_tc3_cons;
	  break;

	case scm_tcs_struct:
	  tag = scm_tc3_struct;
	  break;
	case scm_tcs_closures:
	  tag = scm_tc3_closure;
	  break;
	case scm_tcs_subrs:
	  tag = scm_tc7_asubr;
	  break;
	}

      {      
        SCM handle = scm_hashq_create_handle_x (hashtab,
                                                scm_from_int (tag), SCM_INUM0);
        SCM_SETCDR (handle, scm_from_int (scm_to_int (SCM_CDR (handle)) + 1));
      }
    }
}

/* TAG is the tag word of a cell, return a string which is its name, or NULL
   if unknown.  Currently this is only used by gc-live-object-stats and the
   distinctions between types are oriented towards what that code records
   while scanning what's alive.  */
char const *
scm_i_tag_name (scm_t_bits tag)
{
  switch (tag & 0x7F) /* 7 bits */
    {
    case scm_tcs_struct:
      return "struct";
    case scm_tcs_cons_imcar:
      return "cons (immediate car)";
    case scm_tcs_cons_nimcar:
      return "cons (non-immediate car)";
    case scm_tcs_closures:
      return "closures";
    case scm_tc7_pws:
      return "pws";
    case scm_tc7_wvect:
      return "weak vector";
    case scm_tc7_vector:
      return "vector";
    case scm_tc7_number:
      switch (tag)
	{
	case scm_tc16_real:
	  return "real";
	case scm_tc16_big:
	  return "bignum";
	case scm_tc16_complex:
	  return "complex number";
	case scm_tc16_fraction:
	  return "fraction";
	}
      /* shouldn't reach here unless there's a new class of numbers */
      return "number";
    case scm_tc7_string:
      return "string";
    case scm_tc7_stringbuf:
      return "string buffer";
    case scm_tc7_symbol:
      return "symbol";
    case scm_tc7_variable:
      return "variable";
    case scm_tcs_subrs:
      return "subrs";
    case scm_tc7_port:
      return "port";
    case scm_tc7_smob:
      /* scm_tc_free_cell is smob 0, the name field in that scm_smobs[]
         entry should be ok for our return here */
      return scm_smobs[SCM_TC2SMOBNUM (tag)].name;
    }

  return NULL;
}


#if (SCM_DEBUG_DEBUGGING_SUPPORT == 1)

typedef struct scm_dbg_t_list_cell {
  scm_t_bits car;  
  struct scm_dbg_t_list_cell * cdr;
} scm_dbg_t_list_cell;


typedef struct scm_dbg_t_double_cell {
  scm_t_bits word_0;
  scm_t_bits word_1;
  scm_t_bits word_2;
  scm_t_bits word_3;
} scm_dbg_t_double_cell;


int scm_dbg_gc_marked_p (SCM obj);
scm_t_cell * scm_dbg_gc_get_card (SCM obj);
scm_t_c_bvec_long * scm_dbg_gc_get_bvec (SCM obj);


int
scm_dbg_gc_marked_p (SCM obj)
{
  if (!SCM_IMP (obj))
    return SCM_GC_MARK_P (obj);
  else
    return 0;
}

scm_t_cell *
scm_dbg_gc_get_card (SCM obj)
{
  if (!SCM_IMP (obj))
    return SCM_GC_CELL_CARD (obj);
  else
    return NULL;
}

scm_t_c_bvec_long *
scm_dbg_gc_get_bvec (SCM obj)
{
  if (!SCM_IMP (obj))
    return SCM_GC_CARD_BVEC (SCM_GC_CELL_CARD (obj));
  else
    return NULL;
}

#endif