Annotation of OpenXM_contrib/gc/gc_cpp.h, Revision 1.1
1.1 ! maekawa 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: Last modified on Mon Jul 24 15:43:42 PDT 1995 by ellis
! 20:
! 21: This interface provides access to the Boehm collector. It provides
! 22: basic facilities similar to those described in "Safe, Efficient
! 23: Garbage Collection for C++", by John R. Elis and David L. Detlefs
! 24: (ftp.parc.xerox.com:/pub/ellis/gc).
! 25:
! 26: All heap-allocated objects are either "collectable" or
! 27: "uncollectable". Programs must explicitly delete uncollectable
! 28: objects, whereas the garbage collector will automatically delete
! 29: collectable objects when it discovers them to be inaccessible.
! 30: Collectable objects may freely point at uncollectable objects and vice
! 31: versa.
! 32:
! 33: Objects allocated with the built-in "::operator new" are uncollectable.
! 34:
! 35: Objects derived from class "gc" are collectable. For example:
! 36:
! 37: class A: public gc {...};
! 38: A* a = new A; // a is collectable.
! 39:
! 40: Collectable instances of non-class types can be allocated using the GC
! 41: placement:
! 42:
! 43: typedef int A[ 10 ];
! 44: A* a = new (GC) A;
! 45:
! 46: Uncollectable instances of classes derived from "gc" can be allocated
! 47: using the NoGC placement:
! 48:
! 49: class A: public gc {...};
! 50: A* a = new (NoGC) A; // a is uncollectable.
! 51:
! 52: Both uncollectable and collectable objects can be explicitly deleted
! 53: with "delete", which invokes an object's destructors and frees its
! 54: storage immediately.
! 55:
! 56: A collectable object may have a clean-up function, which will be
! 57: invoked when the collector discovers the object to be inaccessible.
! 58: An object derived from "gc_cleanup" or containing a member derived
! 59: from "gc_cleanup" has a default clean-up function that invokes the
! 60: object's destructors. Explicit clean-up functions may be specified as
! 61: an additional placement argument:
! 62:
! 63: A* a = ::new (GC, MyCleanup) A;
! 64:
! 65: An object is considered "accessible" by the collector if it can be
! 66: reached by a path of pointers from static variables, automatic
! 67: variables of active functions, or from some object with clean-up
! 68: enabled; pointers from an object to itself are ignored.
! 69:
! 70: Thus, if objects A and B both have clean-up functions, and A points at
! 71: B, B is considered accessible. After A's clean-up is invoked and its
! 72: storage released, B will then become inaccessible and will have its
! 73: clean-up invoked. If A points at B and B points to A, forming a
! 74: cycle, then that's considered a storage leak, and neither will be
! 75: collectable. See the interface gc.h for low-level facilities for
! 76: handling such cycles of objects with clean-up.
! 77:
! 78: The collector cannot guarrantee that it will find all inaccessible
! 79: objects. In practice, it finds almost all of them.
! 80:
! 81:
! 82: Cautions:
! 83:
! 84: 1. Be sure the collector has been augmented with "make c++".
! 85:
! 86: 2. If your compiler supports the new "operator new[]" syntax, then
! 87: add -DOPERATOR_NEW_ARRAY to the Makefile.
! 88:
! 89: If your compiler doesn't support "operator new[]", beware that an
! 90: array of type T, where T is derived from "gc", may or may not be
! 91: allocated as a collectable object (it depends on the compiler). Use
! 92: the explicit GC placement to make the array collectable. For example:
! 93:
! 94: class A: public gc {...};
! 95: A* a1 = new A[ 10 ]; // collectable or uncollectable?
! 96: A* a2 = new (GC) A[ 10 ]; // collectable
! 97:
! 98: 3. The destructors of collectable arrays of objects derived from
! 99: "gc_cleanup" will not be invoked properly. For example:
! 100:
! 101: class A: public gc_cleanup {...};
! 102: A* a = new (GC) A[ 10 ]; // destructors not invoked correctly
! 103:
! 104: Typically, only the destructor for the first element of the array will
! 105: be invoked when the array is garbage-collected. To get all the
! 106: destructors of any array executed, you must supply an explicit
! 107: clean-up function:
! 108:
! 109: A* a = new (GC, MyCleanUp) A[ 10 ];
! 110:
! 111: (Implementing clean-up of arrays correctly, portably, and in a way
! 112: that preserves the correct exception semantics requires a language
! 113: extension, e.g. the "gc" keyword.)
! 114:
! 115: 4. Compiler bugs:
! 116:
! 117: * Solaris 2's CC (SC3.0) doesn't implement t->~T() correctly, so the
! 118: destructors of classes derived from gc_cleanup won't be invoked.
! 119: You'll have to explicitly register a clean-up function with
! 120: new-placement syntax.
! 121:
! 122: * Evidently cfront 3.0 does not allow destructors to be explicitly
! 123: invoked using the ANSI-conforming syntax t->~T(). If you're using
! 124: cfront 3.0, you'll have to comment out the class gc_cleanup, which
! 125: uses explicit invocation.
! 126:
! 127: ****************************************************************************/
! 128:
! 129: #include "gc.h"
! 130:
! 131: #ifndef THINK_CPLUS
! 132: #define _cdecl
! 133: #endif
! 134:
! 135: #if ! defined( OPERATOR_NEW_ARRAY ) \
! 136: && (__BORLANDC__ >= 0x450 || (__GNUC__ >= 2 && __GNUC_MINOR__ >= 6) \
! 137: || __WATCOMC__ >= 1050)
! 138: # define OPERATOR_NEW_ARRAY
! 139: #endif
! 140:
! 141: enum GCPlacement {GC, NoGC, PointerFreeGC};
! 142:
! 143: class gc {public:
! 144: inline void* operator new( size_t size );
! 145: inline void* operator new( size_t size, GCPlacement gcp );
! 146: inline void operator delete( void* obj );
! 147:
! 148: #ifdef OPERATOR_NEW_ARRAY
! 149: inline void* operator new[]( size_t size );
! 150: inline void* operator new[]( size_t size, GCPlacement gcp );
! 151: inline void operator delete[]( void* obj );
! 152: #endif /* OPERATOR_NEW_ARRAY */
! 153: };
! 154: /*
! 155: Instances of classes derived from "gc" will be allocated in the
! 156: collected heap by default, unless an explicit NoGC placement is
! 157: specified. */
! 158:
! 159: class gc_cleanup: virtual public gc {public:
! 160: inline gc_cleanup();
! 161: inline virtual ~gc_cleanup();
! 162: private:
! 163: inline static void _cdecl cleanup( void* obj, void* clientData );};
! 164: /*
! 165: Instances of classes derived from "gc_cleanup" will be allocated
! 166: in the collected heap by default. When the collector discovers an
! 167: inaccessible object derived from "gc_cleanup" or containing a
! 168: member derived from "gc_cleanup", its destructors will be
! 169: invoked. */
! 170:
! 171: extern "C" {typedef void (*GCCleanUpFunc)( void* obj, void* clientData );}
! 172:
! 173: inline void* operator new(
! 174: size_t size,
! 175: GCPlacement gcp,
! 176: GCCleanUpFunc cleanup = 0,
! 177: void* clientData = 0 );
! 178: /*
! 179: Allocates a collectable or uncollected object, according to the
! 180: value of "gcp".
! 181:
! 182: For collectable objects, if "cleanup" is non-null, then when the
! 183: allocated object "obj" becomes inaccessible, the collector will
! 184: invoke the function "cleanup( obj, clientData )" but will not
! 185: invoke the object's destructors. It is an error to explicitly
! 186: delete an object allocated with a non-null "cleanup".
! 187:
! 188: It is an error to specify a non-null "cleanup" with NoGC or for
! 189: classes derived from "gc_cleanup" or containing members derived
! 190: from "gc_cleanup". */
! 191:
! 192: #ifdef OPERATOR_NEW_ARRAY
! 193:
! 194: inline void* operator new[](
! 195: size_t size,
! 196: GCPlacement gcp,
! 197: GCCleanUpFunc cleanup = 0,
! 198: void* clientData = 0 );
! 199: /*
! 200: The operator new for arrays, identical to the above. */
! 201:
! 202: #endif /* OPERATOR_NEW_ARRAY */
! 203:
! 204: /****************************************************************************
! 205:
! 206: Inline implementation
! 207:
! 208: ****************************************************************************/
! 209:
! 210: inline void* gc::operator new( size_t size ) {
! 211: return GC_MALLOC( size );}
! 212:
! 213: inline void* gc::operator new( size_t size, GCPlacement gcp ) {
! 214: if (gcp == GC)
! 215: return GC_MALLOC( size );
! 216: else if (gcp == PointerFreeGC)
! 217: return GC_MALLOC_ATOMIC( size );
! 218: else
! 219: return GC_MALLOC_UNCOLLECTABLE( size );}
! 220:
! 221: inline void gc::operator delete( void* obj ) {
! 222: GC_FREE( obj );}
! 223:
! 224:
! 225: #ifdef OPERATOR_NEW_ARRAY
! 226:
! 227: inline void* gc::operator new[]( size_t size ) {
! 228: return gc::operator new( size );}
! 229:
! 230: inline void* gc::operator new[]( size_t size, GCPlacement gcp ) {
! 231: return gc::operator new( size, gcp );}
! 232:
! 233: inline void gc::operator delete[]( void* obj ) {
! 234: gc::operator delete( obj );}
! 235:
! 236: #endif /* OPERATOR_NEW_ARRAY */
! 237:
! 238:
! 239: inline gc_cleanup::~gc_cleanup() {
! 240: GC_REGISTER_FINALIZER_IGNORE_SELF( GC_base(this), 0, 0, 0, 0 );}
! 241:
! 242: inline void gc_cleanup::cleanup( void* obj, void* displ ) {
! 243: ((gc_cleanup*) ((char*) obj + (ptrdiff_t) displ))->~gc_cleanup();}
! 244:
! 245: inline gc_cleanup::gc_cleanup() {
! 246: GC_finalization_proc oldProc;
! 247: void* oldData;
! 248: void* base = GC_base( (void *) this );
! 249: if (0 == base) return;
! 250: GC_REGISTER_FINALIZER_IGNORE_SELF(
! 251: base, cleanup, (void*) ((char*) this - (char*) base),
! 252: &oldProc, &oldData );
! 253: if (0 != oldProc) {
! 254: GC_REGISTER_FINALIZER_IGNORE_SELF( base, oldProc, oldData, 0, 0 );}}
! 255:
! 256: inline void* operator new(
! 257: size_t size,
! 258: GCPlacement gcp,
! 259: GCCleanUpFunc cleanup,
! 260: void* clientData )
! 261: {
! 262: void* obj;
! 263:
! 264: if (gcp == GC) {
! 265: obj = GC_MALLOC( size );
! 266: if (cleanup != 0)
! 267: GC_REGISTER_FINALIZER_IGNORE_SELF(
! 268: obj, cleanup, clientData, 0, 0 );}
! 269: else if (gcp == PointerFreeGC) {
! 270: obj = GC_MALLOC_ATOMIC( size );}
! 271: else {
! 272: obj = GC_MALLOC_UNCOLLECTABLE( size );};
! 273: return obj;}
! 274:
! 275:
! 276: #ifdef OPERATOR_NEW_ARRAY
! 277:
! 278: inline void* operator new[](
! 279: size_t size,
! 280: GCPlacement gcp,
! 281: GCCleanUpFunc cleanup,
! 282: void* clientData )
! 283: {
! 284: return ::operator new( size, gcp, cleanup, clientData );}
! 285:
! 286: #endif /* OPERATOR_NEW_ARRAY */
! 287:
! 288:
! 289: #endif /* GC_CPP_H */
! 290:
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