summaryrefslogtreecommitdiff
path: root/libobjc/gc.c
blob: d92c0c3fdc66038e0069435c0c52c05cdc022456 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
/* Basic data types for Objective C.
   Copyright (C) 1998 Free Software Foundation, Inc.
   Contributed by Ovidiu Predescu.

This file is part of GNU CC.

GNU CC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU CC 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* As a special exception, if you link this library with files
   compiled with GCC to produce an executable, this does not cause
   the resulting executable to be covered by the GNU General Public License.
   This exception does not however invalidate any other reasons why
   the executable file might be covered by the GNU General Public License.  */

#include "tconfig.h"
#include "objc.h"
#include "encoding.h"

#include <assert.h>
#include <string.h>

#if OBJC_WITH_GC

#include <gc.h>

/* gc_typed.h uses the following but doesn't declare them */
typedef GC_word word;
typedef GC_signed_word signed_word;

#if BITS_PER_WORD == 32
# define LOGWL	5
# define modWORDSZ(n) ((n) & 0x1f)        /* n mod size of word	    */
#endif

#if BITS_PER_WORD == 64
# define LOGWL 6
# define modWORDSZ(n) ((n) & 0x3f)        /* n mod size of word	    */
#endif

#define divWORDSZ(n) ((n) >> LOGWL)	   /* divide n by size of word      */

#include <gc_typed.h>

/* The following functions set up in `mask` the corresponding pointers.
   The offset is incremented with the size of the type.  */

#define ROUND(V, A) \
  ({ typeof(V) __v=(V); typeof(A) __a=(A); \
     __a*((__v+__a-1)/__a); })

#define SET_BIT_FOR_OFFSET(mask, offset) \
  GC_set_bit(mask, offset / sizeof (void*))

/* Some prototypes */
static void
__objc_gc_setup_struct (GC_bitmap mask, const char *type, int offset);
static void
__objc_gc_setup_union (GC_bitmap mask, const char *type, int offset);


static void
__objc_gc_setup_array (GC_bitmap mask, const char *type, int offset)
{
  int i, len = atoi(type + 1);

  while (isdigit(*++type))
    /* do nothing */;		/* skip the size of the array */

  switch (*type) {
  case _C_ARY_B:
    for (i = 0; i < len; i++)
      __objc_gc_setup_array (mask, type, offset);
    break;

  case _C_STRUCT_B:
    for (i = 0; i < len; i++)
      __objc_gc_setup_struct (mask, type, offset);
    break;

  case _C_UNION_B:
    for (i = 0; i < len; i++)
      __objc_gc_setup_union (mask, type, offset);
    break;

  default:
    break;
  }
}

static void
__objc_gc_setup_struct (GC_bitmap mask, const char *type, int offset)
{
  struct objc_struct_layout layout;
  unsigned int position;
  const char *mtype;

  objc_layout_structure (type, &layout);

  while (objc_layout_structure_next_member (&layout))
    {
      BOOL gc_invisible = NO;

      objc_layout_structure_get_info (&layout, &position, NULL, &mtype);

      /* Skip the variable name */
      if (*mtype == '"')
	{
	  for (mtype++; *mtype++ != '"';)
	    /* do nothing */;
	}

      if (*mtype == _C_GCINVISIBLE)
	{
	  gc_invisible = YES;
	  mtype++;
	}

      /* Add to position the offset of this structure */
      position += offset;

      switch (*mtype) {
      case _C_ID:
      case _C_CLASS:
      case _C_SEL:
      case _C_PTR:
      case _C_CHARPTR:
      case _C_ATOM:
	if (!gc_invisible)
	  SET_BIT_FOR_OFFSET(mask, position);
	break;

      case _C_ARY_B:
	__objc_gc_setup_array (mask, mtype, position);
	break;

      case _C_STRUCT_B:
	__objc_gc_setup_struct (mask, mtype, position);
	break;

      case _C_UNION_B:
	__objc_gc_setup_union (mask, mtype, position);
	break;

      default:
        break;
      }
    }
}

static void
__objc_gc_setup_union (GC_bitmap mask, const char *type, int offset)
{
  /* Sub-optimal, quick implementation: assume the union is made of
     pointers, set up the mask accordingly. */

  int i, size, align;

  /* Skip the variable name */
  if (*type == '"')
    {
      for (type++; *type++ != '"';)
	/* do nothing */;
    }

  size = objc_sizeof_type (type);
  align = objc_alignof_type (type);

  offset = ROUND(offset, align);
  for (i = 0; i < size; i += sizeof (void*))
    {
      SET_BIT_FOR_OFFSET(mask, offset);
      offset += sizeof (void*);
    }
}


/* Iterates over the types in the structure that represents the class
   encoding and sets the bits in mask according to each ivar type.  */
static void
__objc_gc_type_description_from_type (GC_bitmap mask, const char *type)
{
  struct objc_struct_layout layout;
  unsigned int offset, align;
  const char *ivar_type;

  objc_layout_structure (type, &layout);

  while (objc_layout_structure_next_member (&layout))
    {
      BOOL gc_invisible = NO;

      objc_layout_structure_get_info (&layout, &offset, &align, &ivar_type);

      /* Skip the variable name */
      if (*ivar_type == '"')
	{
	  for (ivar_type++; *ivar_type++ != '"';)
	    /* do nothing */;
	}

      if (*ivar_type == _C_GCINVISIBLE)
	{
	  gc_invisible = YES;
	  ivar_type++;
	}

      switch (*ivar_type) {
      case _C_ID:
      case _C_CLASS:
      case _C_SEL:
      case _C_PTR:
      case _C_CHARPTR:
        if (!gc_invisible)
          SET_BIT_FOR_OFFSET(mask, offset);
	break;

      case _C_ARY_B:
	__objc_gc_setup_array (mask, ivar_type, offset);
	break;

      case _C_STRUCT_B:
	__objc_gc_setup_struct (mask, ivar_type, offset);
	break;

      case _C_UNION_B:
	__objc_gc_setup_union (mask, ivar_type, offset);
	break;

      default:
        break;
      }
    }
}

/* Computes in *type the full type encoding of this class including
   its super classes. '*size' gives the total number of bytes allocated
   into *type, '*current' the number of bytes used so far by the
   encoding. */
static void
__objc_class_structure_encoding (Class class, char **type, int *size,
                                 int *current)
{
  int i, ivar_count;
  struct objc_ivar_list* ivars;

  if (!class)
    {
      strcat (*type, "{");
      *current++;
      return;
    }

  /* Add the type encodings of the super classes */
  __objc_class_structure_encoding (class->super_class, type, size, current);

  ivars = class->ivars;
  if (!ivars)
    return;

  ivar_count = ivars->ivar_count;

  for (i = 0; i < ivar_count; i++)
    {
      struct objc_ivar *ivar = &(ivars->ivar_list[i]);
      const char *ivar_type = ivar->ivar_type;
      int len = strlen (ivar_type);

      if (*current + len + 1 >= *size)
        {
          /* Increase the size of the encoding string so that it
             contains this ivar's type. */
          *size = ROUND(*current + len + 1, 10);
          *type = objc_realloc (*type, *size);
        }
      strcat (*type + *current, ivar_type);
      *current += len;
    }
}


/* Allocates the memory that will hold the type description for class
   and calls the __objc_class_structure_encoding that generates this
   value. */
void
__objc_generate_gc_type_description (Class class)
{
  GC_bitmap mask;
  int bits_no, size;
  int type_size = 10, current;
  char *class_structure_type;

  if (!CLS_ISCLASS(class))
    return;

  /* We have to create a mask in which each bit counts for a pointer member.
     We take into consideration all the non-pointer instance variables and we
     round them up to the alignment. */

  /* The number of bits in the mask is the size of an instance in bytes divided
     by the size of a pointer. */
  bits_no = (ROUND(class_get_instance_size (class), sizeof(void*))
             / sizeof (void*));
  size = ROUND(bits_no, BITS_PER_WORD) / BITS_PER_WORD;
  mask = objc_atomic_malloc (size * sizeof (int));
  memset (mask, 0, size * sizeof (int));

  class_structure_type = objc_atomic_malloc (type_size);
  *class_structure_type = current = 0;
  __objc_class_structure_encoding (class, &class_structure_type,
                                   &type_size, &current);
  if (current + 1 == type_size)
    class_structure_type = objc_realloc (class_structure_type, ++type_size);
  strcat (class_structure_type + current, "}");
#ifdef DEBUG
  printf ("type description for '%s' is %s\n", class->name, class_structure_type);
#endif
  
  __objc_gc_type_description_from_type (mask, class_structure_type);
  objc_free (class_structure_type);

#ifdef DEBUG
  printf ("  mask for '%s', type '%s' (bits %d, mask size %d) is:",
	  class_structure_type, class->name, bits_no, size);
  {
    int i;
    for (i = 0; i < size; i++)
      printf (" %lx", mask[i]);
  }
  puts ("");
#endif

  class->gc_object_type = (void*)GC_make_descriptor (mask, bits_no);
}


/* Returns YES if type denotes a pointer type, NO otherwise */
static inline BOOL
__objc_ivar_pointer (const char *type)
{
  type = objc_skip_type_qualifiers (type);

  return (*type == _C_ID
          || *type == _C_CLASS
          || *type == _C_SEL
          || *type == _C_PTR
          || *type == _C_CHARPTR
          || *type == _C_ATOM);
}


/* Mark the instance variable whose name is given by ivarname as a
   weak pointer (a pointer hidden to the garbage collector) if
   gc_invisible is true. If gc_invisible is false it unmarks the
   instance variable and makes it a normal pointer, visible to the
   garbage collector.

   This operation only makes sense on instance variables that are
   pointers.  */
void
class_ivar_set_gcinvisible (Class class, const char* ivarname,
                            BOOL gc_invisible)
{
  int i, ivar_count;
  struct objc_ivar_list* ivars;

  if (!class || !ivarname)
    return;

  ivars = class->ivars;
  if (!ivars)
    return;

  ivar_count = ivars->ivar_count;

  for (i = 0; i < ivar_count; i++)
    {
      struct objc_ivar *ivar = &(ivars->ivar_list[i]);
      const char *type;

      if (!ivar->ivar_name || strcmp (ivar->ivar_name, ivarname))
	continue;

      assert (ivar->ivar_type);
      type = ivar->ivar_type;

      /* Skip the variable name */
      if (*type == '"')
	{
	  for (type++; *type++ != '"';)
	    /* do nothing */;
	}

      if (*type == _C_GCINVISIBLE)
	{
	  char *new_type;

	  if (gc_invisible || !__objc_ivar_pointer (type))
	    return;	/* The type of the variable already matches the
			   requested gc_invisible type */

	  /* The variable is gc_invisible and we have to reverse it */
	  new_type = objc_atomic_malloc (strlen (ivar->ivar_type));
	  strncpy (new_type, ivar->ivar_type,
		   (size_t)(type - ivar->ivar_type));
	  strcat (new_type, type + 1);
	  ivar->ivar_type = new_type;
	}
      else
	{
	  char *new_type;

	  if (!gc_invisible || !__objc_ivar_pointer (type))
	    return;	/* The type of the variable already matches the
			   requested gc_invisible type */

	  /* The variable is gc visible and we have to make it gc_invisible */
	  new_type = objc_malloc (strlen (ivar->ivar_type) + 2);
	  strncpy (new_type, ivar->ivar_type,
		   (size_t)(type - ivar->ivar_type));
	  strcat (new_type, "!");
	  strcat (new_type, type);
	  ivar->ivar_type = new_type;
	}

      __objc_generate_gc_type_description (class);
      return;
    }

  /* Search the instance variable in the superclasses */
  class_ivar_set_gcinvisible (class->super_class, ivarname, gc_invisible);
}

#else /* !OBJC_WITH_GC */

void
__objc_generate_gc_type_description (Class class)
{
}

void class_ivar_set_gcinvisible (Class class,
				 const char* ivarname,
				 BOOL gc_invisible)
{
}

#endif /* OBJC_WITH_GC */