ceph/src/boost/tools/build/src/engine/boehm_gc/include/gc_cpp.h

   1 #ifndef GC_CPP_H
   2 #define GC_CPP_H
   3 /****************************************************************************
   4 Copyright (c) 1994 by Xerox Corporation.  All rights reserved.
   5
   6 THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   7 OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   8
   9 Permission is hereby granted to use or copy this program for any
  10 purpose, provided the above notices are retained on all copies.
  11 Permission to modify the code and to distribute modified code is
  12 granted, provided the above notices are retained, and a notice that
  13 the code was modified is included with the above copyright notice.
  14 ****************************************************************************
  15
  16 C++ Interface to the Boehm Collector
  17
  18     John R. Ellis and Jesse Hull
  19
  20 This interface provides access to the Boehm collector.  It provides
  21 basic facilities similar to those described in "Safe, Efficient
  22 Garbage Collection for C++", by John R. Elis and David L. Detlefs
  23 (ftp://ftp.parc.xerox.com/pub/ellis/gc).
  24
  25 All heap-allocated objects are either "collectable" or
  26 "uncollectable".  Programs must explicitly delete uncollectable
  27 objects, whereas the garbage collector will automatically delete
  28 collectable objects when it discovers them to be inaccessible.
  29 Collectable objects may freely point at uncollectable objects and vice
  30 versa.
  31
  32 Objects allocated with the built-in "::operator new" are uncollectable.
  33
  34 Objects derived from class "gc" are collectable.  For example:
  35
  36     class A: public gc {...};
  37     A* a = new A;       // a is collectable.
  38
  39 Collectable instances of non-class types can be allocated using the GC
  40 (or UseGC) placement:
  41
  42     typedef int A[ 10 ];
  43     A* a = new (GC) A;
  44
  45 Uncollectable instances of classes derived from "gc" can be allocated
  46 using the NoGC placement:
  47
  48     class A: public gc {...};
  49     A* a = new (NoGC) A;   // a is uncollectable.
  50
  51 The new(PointerFreeGC) syntax allows the allocation of collectable
  52 objects that are not scanned by the collector.  This useful if you
  53 are allocating compressed data, bitmaps, or network packets.  (In
  54 the latter case, it may remove danger of unfriendly network packets
  55 intentionally containing values that cause spurious memory retention.)
  56
  57 Both uncollectable and collectable objects can be explicitly deleted
  58 with "delete", which invokes an object's destructors and frees its
  59 storage immediately.
  60
  61 A collectable object may have a clean-up function, which will be
  62 invoked when the collector discovers the object to be inaccessible.
  63 An object derived from "gc_cleanup" or containing a member derived
  64 from "gc_cleanup" has a default clean-up function that invokes the
  65 object's destructors.  Explicit clean-up functions may be specified as
  66 an additional placement argument:
  67
  68     A* a = ::new (GC, MyCleanup) A;
  69
  70 An object is considered "accessible" by the collector if it can be
  71 reached by a path of pointers from static variables, automatic
  72 variables of active functions, or from some object with clean-up
  73 enabled; pointers from an object to itself are ignored.
  74
  75 Thus, if objects A and B both have clean-up functions, and A points at
  76 B, B is considered accessible.  After A's clean-up is invoked and its
  77 storage released, B will then become inaccessible and will have its
  78 clean-up invoked.  If A points at B and B points to A, forming a
  79 cycle, then that's considered a storage leak, and neither will be
  80 collectable.  See the interface gc.h for low-level facilities for
  81 handling such cycles of objects with clean-up.
  82
  83 The collector cannot guarantee that it will find all inaccessible
  84 objects.  In practice, it finds almost all of them.
  85
  86
  87 Cautions:
  88
  89 1. Be sure the collector has been augmented with "make c++" or
  90 "--enable-cplusplus".
  91
  92 2.  If your compiler supports the new "operator new[]" syntax, then
  93 add -DGC_OPERATOR_NEW_ARRAY to the Makefile.
  94
  95 If your compiler doesn't support "operator new[]", beware that an
  96 array of type T, where T is derived from "gc", may or may not be
  97 allocated as a collectable object (it depends on the compiler).  Use
  98 the explicit GC placement to make the array collectable.  For example:
  99
 100     class A: public gc {...};
 101     A* a1 = new A[ 10 ];        // collectable or uncollectable?
 102     A* a2 = new (GC) A[ 10 ];   // collectable
 103
 104 3. The destructors of collectable arrays of objects derived from
 105 "gc_cleanup" will not be invoked properly.  For example:
 106
 107     class A: public gc_cleanup {...};
 108     A* a = new (GC) A[ 10 ];    // destructors not invoked correctly
 109
 110 Typically, only the destructor for the first element of the array will
 111 be invoked when the array is garbage-collected.  To get all the
 112 destructors of any array executed, you must supply an explicit
 113 clean-up function:
 114
 115     A* a = new (GC, MyCleanUp) A[ 10 ];
 116
 117 (Implementing clean-up of arrays correctly, portably, and in a way
 118 that preserves the correct exception semantics requires a language
 119 extension, e.g. the "gc" keyword.)
 120
 121 4. Compiler bugs (now hopefully history):
 122
 123 * Solaris 2's CC (SC3.0) doesn't implement t->~T() correctly, so the
 124 destructors of classes derived from gc_cleanup won't be invoked.
 125 You'll have to explicitly register a clean-up function with
 126 new-placement syntax.
 127
 128 * Evidently cfront 3.0 does not allow destructors to be explicitly
 129 invoked using the ANSI-conforming syntax t->~T().  If you're using
 130 cfront 3.0, you'll have to comment out the class gc_cleanup, which
 131 uses explicit invocation.
 132
 133 5. GC name conflicts:
 134
 135 Many other systems seem to use the identifier "GC" as an abbreviation
 136 for "Graphics Context".  Since version 5.0, GC placement has been replaced
 137 by UseGC.  GC is an alias for UseGC, unless GC_NAME_CONFLICT is defined.
 138
 139 ****************************************************************************/
 140
 141 #include "gc.h"
 142
 143 #ifndef THINK_CPLUS
 144 #  define GC_cdecl
 145 #else
 146 #  define GC_cdecl _cdecl
 147 #endif
 148
 149 #if ! defined( GC_NO_OPERATOR_NEW_ARRAY ) \
 150     && !defined(_ENABLE_ARRAYNEW) /* Digimars */ \
 151     && (defined(__BORLANDC__) && (__BORLANDC__ < 0x450) \
 152         || (defined(__GNUC__) && \
 153             (__GNUC__ < 2 || __GNUC__ == 2 && __GNUC_MINOR__ < 6)) \
 154         || (defined(__WATCOMC__) && __WATCOMC__ < 1050))
 155 #   define GC_NO_OPERATOR_NEW_ARRAY
 156 #endif
 157
 158 #if !defined(GC_NO_OPERATOR_NEW_ARRAY) && !defined(GC_OPERATOR_NEW_ARRAY)
 159 #   define GC_OPERATOR_NEW_ARRAY
 160 #endif
 161
 162 #if    ! defined ( __BORLANDC__ )  /* Confuses the Borland compiler. */ \
 163     && ! defined ( __sgi )
 164 #  define GC_PLACEMENT_DELETE
 165 #endif
 166
 167 enum GCPlacement {UseGC,
 168 #ifndef GC_NAME_CONFLICT
 169                   GC=UseGC,
 170 #endif
 171                   NoGC, PointerFreeGC};
 172
 173 class gc {public:
 174     inline void* operator new( size_t size );
 175     inline void* operator new( size_t size, GCPlacement gcp );
 176     inline void* operator new( size_t size, void *p );
 177         /* Must be redefined here, since the other overloadings */
 178         /* hide the global definition.                          */
 179     inline void operator delete( void* obj );
 180 #   ifdef GC_PLACEMENT_DELETE
 181       inline void operator delete( void*, void* );
 182 #   endif
 183
 184 #ifdef GC_OPERATOR_NEW_ARRAY
 185     inline void* operator new[]( size_t size );
 186     inline void* operator new[]( size_t size, GCPlacement gcp );
 187     inline void* operator new[]( size_t size, void *p );
 188     inline void operator delete[]( void* obj );
 189 #   ifdef GC_PLACEMENT_DELETE
 190       inline void operator delete[]( void*, void* );
 191 #   endif
 192 #endif /* GC_OPERATOR_NEW_ARRAY */
 193     };
 194     /*
 195     Instances of classes derived from "gc" will be allocated in the
 196     collected heap by default, unless an explicit NoGC placement is
 197     specified. */
 198
 199 class gc_cleanup: virtual public gc {public:
 200     inline gc_cleanup();
 201     inline virtual ~gc_cleanup();
 202 private:
 203     inline static void GC_cdecl cleanup( void* obj, void* clientData );};
 204     /*
 205     Instances of classes derived from "gc_cleanup" will be allocated
 206     in the collected heap by default.  When the collector discovers an
 207     inaccessible object derived from "gc_cleanup" or containing a
 208     member derived from "gc_cleanup", its destructors will be
 209     invoked. */
 210
 211 extern "C" {typedef void (*GCCleanUpFunc)( void* obj, void* clientData );}
 212
 213 #ifdef _MSC_VER
 214   // Disable warning that "no matching operator delete found; memory will
 215   // not be freed if initialization throws an exception"
 216 # pragma warning(disable:4291)
 217 #endif
 218
 219 inline void* operator new(
 220     size_t size,
 221     GCPlacement gcp,
 222     GCCleanUpFunc cleanup = 0,
 223     void* clientData = 0 );
 224     /*
 225     Allocates a collectable or uncollected object, according to the
 226     value of "gcp".
 227
 228     For collectable objects, if "cleanup" is non-null, then when the
 229     allocated object "obj" becomes inaccessible, the collector will
 230     invoke the function "cleanup( obj, clientData )" but will not
 231     invoke the object's destructors.  It is an error to explicitly
 232     delete an object allocated with a non-null "cleanup".
 233
 234     It is an error to specify a non-null "cleanup" with NoGC or for
 235     classes derived from "gc_cleanup" or containing members derived
 236     from "gc_cleanup". */
 237
 238
 239 #ifdef _MSC_VER
 240  /** This ensures that the system default operator new[] doesn't get
 241   *  undefined, which is what seems to happen on VC++ 6 for some reason
 242   *  if we define a multi-argument operator new[].
 243   *  There seems to be really redirect new in this environment without
 244   *  including this everywhere.
 245   */
 246  void *operator new[]( size_t size );
 247
 248  void operator delete[](void* obj);
 249
 250  void* operator new( size_t size);
 251
 252  void operator delete(void* obj);
 253
 254  // This new operator is used by VC++ in case of Debug builds !
 255  void* operator new(  size_t size,
 256                       int ,//nBlockUse,
 257                       const char * szFileName,
 258                       int nLine );
 259 #endif /* _MSC_VER */
 260
 261
 262 #ifdef GC_OPERATOR_NEW_ARRAY
 263
 264 inline void* operator new[](
 265     size_t size,
 266     GCPlacement gcp,
 267     GCCleanUpFunc cleanup = 0,
 268     void* clientData = 0 );
 269     /*
 270     The operator new for arrays, identical to the above. */
 271
 272 #endif /* GC_OPERATOR_NEW_ARRAY */
 273
 274 /****************************************************************************
 275
 276 Inline implementation
 277
 278 ****************************************************************************/
 279
 280 inline void* gc::operator new( size_t size ) {
 281     return GC_MALLOC( size );}
 282
 283 inline void* gc::operator new( size_t size, GCPlacement gcp ) {
 284     if (gcp == UseGC)
 285         return GC_MALLOC( size );
 286     else if (gcp == PointerFreeGC)
 287         return GC_MALLOC_ATOMIC( size );
 288     else
 289         return GC_MALLOC_UNCOLLECTABLE( size );}
 290
 291 inline void* gc::operator new( size_t size, void *p ) {
 292     return p;}
 293
 294 inline void gc::operator delete( void* obj ) {
 295     GC_FREE( obj );}
 296
 297 #ifdef GC_PLACEMENT_DELETE
 298   inline void gc::operator delete( void*, void* ) {}
 299 #endif
 300
 301 #ifdef GC_OPERATOR_NEW_ARRAY
 302
 303 inline void* gc::operator new[]( size_t size ) {
 304     return gc::operator new( size );}
 305
 306 inline void* gc::operator new[]( size_t size, GCPlacement gcp ) {
 307     return gc::operator new( size, gcp );}
 308
 309 inline void* gc::operator new[]( size_t size, void *p ) {
 310     return p;}
 311
 312 inline void gc::operator delete[]( void* obj ) {
 313     gc::operator delete( obj );}
 314
 315 #ifdef GC_PLACEMENT_DELETE
 316   inline void gc::operator delete[]( void*, void* ) {}
 317 #endif
 318
 319 #endif /* GC_OPERATOR_NEW_ARRAY */
 320
 321
 322 inline gc_cleanup::~gc_cleanup() {
 323     GC_register_finalizer_ignore_self( GC_base(this), 0, 0, 0, 0 );}
 324
 325 inline void gc_cleanup::cleanup( void* obj, void* displ ) {
 326     ((gc_cleanup*) ((char*) obj + (ptrdiff_t) displ))->~gc_cleanup();}
 327
 328 inline gc_cleanup::gc_cleanup() {
 329     GC_finalization_proc oldProc;
 330     void* oldData;
 331     void* base = GC_base( (void *) this );
 332     if (0 != base)  {
 333       // Don't call the debug version, since this is a real base address.
 334       GC_register_finalizer_ignore_self(
 335         base, (GC_finalization_proc)cleanup, (void*) ((char*) this - (char*) base),
 336         &oldProc, &oldData );
 337       if (0 != oldProc) {
 338         GC_register_finalizer_ignore_self( base, oldProc, oldData, 0, 0 );}}}
 339
 340 inline void* operator new(
 341     size_t size,
 342     GCPlacement gcp,
 343     GCCleanUpFunc cleanup,
 344     void* clientData )
 345 {
 346     void* obj;
 347
 348     if (gcp == UseGC) {
 349         obj = GC_MALLOC( size );
 350         if (cleanup != 0)
 351             GC_REGISTER_FINALIZER_IGNORE_SELF(
 352                 obj, cleanup, clientData, 0, 0 );}
 353     else if (gcp == PointerFreeGC) {
 354         obj = GC_MALLOC_ATOMIC( size );}
 355     else {
 356         obj = GC_MALLOC_UNCOLLECTABLE( size );};
 357     return obj;}
 358
 359
 360 #ifdef GC_OPERATOR_NEW_ARRAY
 361
 362 inline void* operator new[](
 363     size_t size,
 364     GCPlacement gcp,
 365     GCCleanUpFunc cleanup,
 366     void* clientData )
 367 {
 368     return ::operator new( size, gcp, cleanup, clientData );}
 369
 370 #endif /* GC_OPERATOR_NEW_ARRAY */
 371
 372
 373 #endif /* GC_CPP_H */
 374