libobjc/gc.c

   1 /* Basic data types for Objective C.
   2    Copyright (C) 1998, 2002, 2004, 2005, 2006, 2009, 2010
   3    Free Software Foundation, Inc.
   4    Contributed by Ovidiu Predescu.
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 3, or (at your option)
  11 any later version.
  12
  13 GCC is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 Under Section 7 of GPL version 3, you are granted additional
  19 permissions described in the GCC Runtime Library Exception, version
  20 3.1, as published by the Free Software Foundation.
  21
  22 You should have received a copy of the GNU General Public License and
  23 a copy of the GCC Runtime Library Exception along with this program;
  24 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  25 <http://www.gnu.org/licenses/>.  */
  26
  27 #include "objc-private/common.h"
  28 #include "objc/objc.h"
  29
  30 #if OBJC_WITH_GC
  31
  32 #include "tconfig.h"
  33 #include <assert.h>
  34 #include <string.h>
  35 #include <stdlib.h>
  36 #include "objc/encoding.h"
  37
  38 #include <gc.h>
  39 #include <limits.h>
  40
  41 /* gc_typed.h uses the following but doesn't declare them */
  42 typedef GC_word word;
  43 typedef GC_signed_word signed_word;
  44 #define BITS_PER_WORD (CHAR_BIT * sizeof (word))
  45
  46 #include <gc_typed.h>
  47
  48 /* The following functions set up in `mask` the corresponding pointers.
  49    The offset is incremented with the size of the type.  */
  50
  51 #define ROUND(V, A) \
  52   ({ typeof (V) __v = (V); typeof (A) __a = (A); \
  53      __a * ((__v+__a - 1)/__a); })
  54
  55 #define SET_BIT_FOR_OFFSET(mask, offset) \
  56   GC_set_bit (mask, offset / sizeof (void *))
  57
  58 /* Some prototypes */
  59 static void
  60 __objc_gc_setup_struct (GC_bitmap mask, const char *type, int offset);
  61 static void
  62 __objc_gc_setup_union (GC_bitmap mask, const char *type, int offset);
  63
  64
  65 static void
  66 __objc_gc_setup_array (GC_bitmap mask, const char *type, int offset)
  67 {
  68   int i, len = atoi (type + 1);
  69
  70   while (isdigit (*++type))
  71     /* do nothing */;           /* skip the size of the array */
  72
  73   switch (*type) {
  74   case _C_ARY_B:
  75     for (i = 0; i < len; i++)
  76       __objc_gc_setup_array (mask, type, offset);
  77     break;
  78
  79   case _C_STRUCT_B:
  80     for (i = 0; i < len; i++)
  81       __objc_gc_setup_struct (mask, type, offset);
  82     break;
  83
  84   case _C_UNION_B:
  85     for (i = 0; i < len; i++)
  86       __objc_gc_setup_union (mask, type, offset);
  87     break;
  88
  89   default:
  90     break;
  91   }
  92 }
  93
  94 static void
  95 __objc_gc_setup_struct (GC_bitmap mask, const char *type, int offset)
  96 {
  97   struct objc_struct_layout layout;
  98   unsigned int position;
  99   const char *mtype;
 100
 101   objc_layout_structure (type, &layout);
 102
 103   while (objc_layout_structure_next_member (&layout))
 104     {
 105       BOOL gc_invisible = NO;
 106
 107       objc_layout_structure_get_info (&layout, &position, NULL, &mtype);
 108
 109       /* Skip the variable name */
 110       if (*mtype == '"')
 111         {
 112           for (mtype++; *mtype++ != '"';)
 113             /* do nothing */;
 114         }
 115
 116       if (*mtype == _C_GCINVISIBLE)
 117         {
 118           gc_invisible = YES;
 119           mtype++;
 120         }
 121
 122       /* Add to position the offset of this structure */
 123       position += offset;
 124
 125       switch (*mtype) {
 126       case _C_ID:
 127       case _C_CLASS:
 128       case _C_SEL:
 129       case _C_PTR:
 130       case _C_CHARPTR:
 131       case _C_ATOM:
 132         if (! gc_invisible)
 133           SET_BIT_FOR_OFFSET (mask, position);
 134         break;
 135
 136       case _C_ARY_B:
 137         __objc_gc_setup_array (mask, mtype, position);
 138         break;
 139
 140       case _C_STRUCT_B:
 141         __objc_gc_setup_struct (mask, mtype, position);
 142         break;
 143
 144       case _C_UNION_B:
 145         __objc_gc_setup_union (mask, mtype, position);
 146         break;
 147
 148       default:
 149         break;
 150       }
 151     }
 152 }
 153
 154 static void
 155 __objc_gc_setup_union (GC_bitmap mask, const char *type, int offset)
 156 {
 157   /* Sub-optimal, quick implementation: assume the union is made of
 158      pointers, set up the mask accordingly. */
 159
 160   int i, size, align;
 161
 162   /* Skip the variable name */
 163   if (*type == '"')
 164     {
 165       for (type++; *type++ != '"';)
 166         /* do nothing */;
 167     }
 168
 169   size = objc_sizeof_type (type);
 170   align = objc_alignof_type (type);
 171
 172   offset = ROUND (offset, align);
 173   for (i = 0; i < size; i += sizeof (void *))
 174     {
 175       SET_BIT_FOR_OFFSET (mask, offset);
 176       offset += sizeof (void *);
 177     }
 178 }
 179
 180
 181 /* Iterates over the types in the structure that represents the class
 182    encoding and sets the bits in mask according to each ivar type.  */
 183 static void
 184 __objc_gc_type_description_from_type (GC_bitmap mask, const char *type)
 185 {
 186   struct objc_struct_layout layout;
 187   unsigned int offset, align;
 188   const char *ivar_type;
 189
 190   objc_layout_structure (type, &layout);
 191
 192   while (objc_layout_structure_next_member (&layout))
 193     {
 194       BOOL gc_invisible = NO;
 195
 196       objc_layout_structure_get_info (&layout, &offset, &align, &ivar_type);
 197
 198       /* Skip the variable name */
 199       if (*ivar_type == '"')
 200         {
 201           for (ivar_type++; *ivar_type++ != '"';)
 202             /* do nothing */;
 203         }
 204
 205       if (*ivar_type == _C_GCINVISIBLE)
 206         {
 207           gc_invisible = YES;
 208           ivar_type++;
 209         }
 210
 211       switch (*ivar_type) {
 212       case _C_ID:
 213       case _C_CLASS:
 214       case _C_SEL:
 215       case _C_PTR:
 216       case _C_CHARPTR:
 217         if (! gc_invisible)
 218           SET_BIT_FOR_OFFSET (mask, offset);
 219         break;
 220
 221       case _C_ARY_B:
 222         __objc_gc_setup_array (mask, ivar_type, offset);
 223         break;
 224
 225       case _C_STRUCT_B:
 226         __objc_gc_setup_struct (mask, ivar_type, offset);
 227         break;
 228
 229       case _C_UNION_B:
 230         __objc_gc_setup_union (mask, ivar_type, offset);
 231         break;
 232
 233       default:
 234         break;
 235       }
 236     }
 237 }
 238
 239 /* Computes in *type the full type encoding of this class including
 240    its super classes. '*size' gives the total number of bytes allocated
 241    into *type, '*current' the number of bytes used so far by the
 242    encoding. */
 243 static void
 244 __objc_class_structure_encoding (Class class, char **type, int *size,
 245                                  int *current)
 246 {
 247   int i, ivar_count;
 248   struct objc_ivar_list *ivars;
 249
 250   if (! class)
 251     {
 252       strcat (*type, "{");
 253       (*current)++;
 254       return;
 255     }
 256
 257   /* Add the type encodings of the super classes */
 258   __objc_class_structure_encoding (class->super_class, type, size, current);
 259
 260   ivars = class->ivars;
 261   if (! ivars)
 262     return;
 263
 264   ivar_count = ivars->ivar_count;
 265
 266   for (i = 0; i < ivar_count; i++)
 267     {
 268       struct objc_ivar *ivar = &(ivars->ivar_list[i]);
 269       const char *ivar_type = ivar->ivar_type;
 270       int len = strlen (ivar_type);
 271
 272       if (*current + len + 1 >= *size)
 273         {
 274           /* Increase the size of the encoding string so that it
 275              contains this ivar's type. */
 276           *size = ROUND (*current + len + 1, 10);
 277           *type = objc_realloc (*type, *size);
 278         }
 279       strcat (*type + *current, ivar_type);
 280       *current += len;
 281     }
 282 }
 283
 284
 285 /* Allocates the memory that will hold the type description for class
 286    and calls the __objc_class_structure_encoding that generates this
 287    value. */
 288 void
 289 __objc_generate_gc_type_description (Class class)
 290 {
 291   GC_bitmap mask;
 292   int bits_no, size;
 293   int type_size = 10, current;
 294   char *class_structure_type;
 295
 296   if (! CLS_ISCLASS (class))
 297     return;
 298
 299   /* We have to create a mask in which each bit counts for a pointer member.
 300      We take into consideration all the non-pointer instance variables and we
 301      round them up to the alignment. */
 302
 303   /* The number of bits in the mask is the size of an instance in bytes divided
 304      by the size of a pointer. */
 305   bits_no = (ROUND (class_get_instance_size (class), sizeof (void *))
 306              / sizeof (void *));
 307   size = ROUND (bits_no, BITS_PER_WORD) / BITS_PER_WORD;
 308   mask = objc_atomic_malloc (size * sizeof (int));
 309   memset (mask, 0, size * sizeof (int));
 310
 311   class_structure_type = objc_atomic_malloc (type_size);
 312   *class_structure_type = current = 0;
 313   __objc_class_structure_encoding (class, &class_structure_type,
 314                                    &type_size, &current);
 315   if (current + 1 == type_size)
 316     class_structure_type = objc_realloc (class_structure_type, ++type_size);
 317   strcat (class_structure_type + current, "}");
 318 #ifdef DEBUG
 319   printf ("type description for '%s' is %s\n", class->name, class_structure_type);
 320 #endif
 321
 322   __objc_gc_type_description_from_type (mask, class_structure_type);
 323   objc_free (class_structure_type);
 324
 325 #ifdef DEBUG
 326   printf ("  mask for '%s', type '%s' (bits %d, mask size %d) is:",
 327           class_structure_type, class->name, bits_no, size);
 328   {
 329     int i;
 330     for (i = 0; i < size; i++)
 331       printf (" %lx", mask[i]);
 332   }
 333   puts ("");
 334 #endif
 335
 336   class->gc_object_type = (void *) GC_make_descriptor (mask, bits_no);
 337 }
 338
 339
 340 /* Returns YES if type denotes a pointer type, NO otherwise */
 341 static inline BOOL
 342 __objc_ivar_pointer (const char *type)
 343 {
 344   type = objc_skip_type_qualifiers (type);
 345
 346   return (*type == _C_ID
 347           || *type == _C_CLASS
 348           || *type == _C_SEL
 349           || *type == _C_PTR
 350           || *type == _C_CHARPTR
 351           || *type == _C_ATOM);
 352 }
 353
 354
 355 /* Mark the instance variable whose name is given by ivarname as a
 356    weak pointer (a pointer hidden to the garbage collector) if
 357    gc_invisible is true. If gc_invisible is false it unmarks the
 358    instance variable and makes it a normal pointer, visible to the
 359    garbage collector.
 360
 361    This operation only makes sense on instance variables that are
 362    pointers.  */
 363 void
 364 class_ivar_set_gcinvisible (Class class, const char *ivarname,
 365                             BOOL gc_invisible)
 366 {
 367   int i, ivar_count;
 368   struct objc_ivar_list *ivars;
 369
 370   if (! class || ! ivarname)
 371     return;
 372
 373   ivars = class->ivars;
 374   if (! ivars)
 375     return;
 376
 377   ivar_count = ivars->ivar_count;
 378
 379   for (i = 0; i < ivar_count; i++)
 380     {
 381       struct objc_ivar *ivar = &(ivars->ivar_list[i]);
 382       const char *type;
 383
 384       if (! ivar->ivar_name || strcmp (ivar->ivar_name, ivarname))
 385         continue;
 386
 387       assert (ivar->ivar_type);
 388       type = ivar->ivar_type;
 389
 390       /* Skip the variable name */
 391       if (*type == '"')
 392         {
 393           for (type++; *type++ != '"';)
 394             /* do nothing */;
 395         }
 396
 397       if (*type == _C_GCINVISIBLE)
 398         {
 399           char *new_type;
 400           size_t len;
 401
 402           if (gc_invisible || ! __objc_ivar_pointer (type))
 403             return;     /* The type of the variable already matches the
 404                            requested gc_invisible type */
 405
 406           /* The variable is gc_invisible so we make it gc visible.  */
 407           new_type = objc_atomic_malloc (strlen(ivar->ivar_type));
 408           len = (type - ivar->ivar_type);
 409           memcpy (new_type, ivar->ivar_type, len);
 410           new_type[len] = 0;
 411           strcat (new_type, type + 1);
 412           ivar->ivar_type = new_type;
 413         }
 414       else
 415         {
 416           char *new_type;
 417           size_t len;
 418
 419           if (! gc_invisible || ! __objc_ivar_pointer (type))
 420             return;     /* The type of the variable already matches the
 421                            requested gc_invisible type */
 422
 423           /* The variable is gc visible so we make it gc_invisible.  */
 424           new_type = objc_malloc (strlen(ivar->ivar_type) + 2);
 425
 426           /* Copy the variable name.  */
 427           len = (type - ivar->ivar_type);
 428           memcpy (new_type, ivar->ivar_type, len);
 429           /* Add '!'.  */
 430           new_type[len++] = _C_GCINVISIBLE;
 431           /* Copy the original types.  */
 432           strcpy (new_type + len, type);
 433
 434           ivar->ivar_type = new_type;
 435         }
 436
 437       __objc_generate_gc_type_description (class);
 438       return;
 439     }
 440
 441   /* Search the instance variable in the superclasses */
 442   class_ivar_set_gcinvisible (class->super_class, ivarname, gc_invisible);
 443 }
 444
 445 #else /* !OBJC_WITH_GC */
 446
 447 void
 448 __objc_generate_gc_type_description (Class class __attribute__ ((__unused__)))
 449 {
 450 }
 451
 452 void class_ivar_set_gcinvisible (Class class __attribute__ ((__unused__)),
 453                                  const char *ivarname __attribute__ ((__unused__)),
 454                                  BOOL gc_invisible __attribute__ ((__unused__)))
 455 {
 456 }
 457
 458 #endif /* OBJC_WITH_GC */