Annotation of OpenXM_contrib2/asir2000/gc5.3/gc_cpp.h, Revision 1.1
1.1 ! noro 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: Both uncollectable and collectable objects can be explicitly deleted
! 52: with "delete", which invokes an object's destructors and frees its
! 53: storage immediately.
! 54:
! 55: A collectable object may have a clean-up function, which will be
! 56: invoked when the collector discovers the object to be inaccessible.
! 57: An object derived from "gc_cleanup" or containing a member derived
! 58: from "gc_cleanup" has a default clean-up function that invokes the
! 59: object's destructors. Explicit clean-up functions may be specified as
! 60: an additional placement argument:
! 61:
! 62: A* a = ::new (GC, MyCleanup) A;
! 63:
! 64: An object is considered "accessible" by the collector if it can be
! 65: reached by a path of pointers from static variables, automatic
! 66: variables of active functions, or from some object with clean-up
! 67: enabled; pointers from an object to itself are ignored.
! 68:
! 69: Thus, if objects A and B both have clean-up functions, and A points at
! 70: B, B is considered accessible. After A's clean-up is invoked and its
! 71: storage released, B will then become inaccessible and will have its
! 72: clean-up invoked. If A points at B and B points to A, forming a
! 73: cycle, then that's considered a storage leak, and neither will be
! 74: collectable. See the interface gc.h for low-level facilities for
! 75: handling such cycles of objects with clean-up.
! 76:
! 77: The collector cannot guarrantee that it will find all inaccessible
! 78: objects. In practice, it finds almost all of them.
! 79:
! 80:
! 81: Cautions:
! 82:
! 83: 1. Be sure the collector has been augmented with "make c++".
! 84:
! 85: 2. If your compiler supports the new "operator new[]" syntax, then
! 86: add -DOPERATOR_NEW_ARRAY to the Makefile.
! 87:
! 88: If your compiler doesn't support "operator new[]", beware that an
! 89: array of type T, where T is derived from "gc", may or may not be
! 90: allocated as a collectable object (it depends on the compiler). Use
! 91: the explicit GC placement to make the array collectable. For example:
! 92:
! 93: class A: public gc {...};
! 94: A* a1 = new A[ 10 ]; // collectable or uncollectable?
! 95: A* a2 = new (GC) A[ 10 ]; // collectable
! 96:
! 97: 3. The destructors of collectable arrays of objects derived from
! 98: "gc_cleanup" will not be invoked properly. For example:
! 99:
! 100: class A: public gc_cleanup {...};
! 101: A* a = new (GC) A[ 10 ]; // destructors not invoked correctly
! 102:
! 103: Typically, only the destructor for the first element of the array will
! 104: be invoked when the array is garbage-collected. To get all the
! 105: destructors of any array executed, you must supply an explicit
! 106: clean-up function:
! 107:
! 108: A* a = new (GC, MyCleanUp) A[ 10 ];
! 109:
! 110: (Implementing clean-up of arrays correctly, portably, and in a way
! 111: that preserves the correct exception semantics requires a language
! 112: extension, e.g. the "gc" keyword.)
! 113:
! 114: 4. Compiler bugs:
! 115:
! 116: * Solaris 2's CC (SC3.0) doesn't implement t->~T() correctly, so the
! 117: destructors of classes derived from gc_cleanup won't be invoked.
! 118: You'll have to explicitly register a clean-up function with
! 119: new-placement syntax.
! 120:
! 121: * Evidently cfront 3.0 does not allow destructors to be explicitly
! 122: invoked using the ANSI-conforming syntax t->~T(). If you're using
! 123: cfront 3.0, you'll have to comment out the class gc_cleanup, which
! 124: uses explicit invocation.
! 125:
! 126: 5. GC name conflicts:
! 127:
! 128: Many other systems seem to use the identifier "GC" as an abbreviation
! 129: for "Graphics Context". Since version 5.0, GC placement has been replaced
! 130: by UseGC. GC is an alias for UseGC, unless GC_NAME_CONFLICT is defined.
! 131:
! 132: ****************************************************************************/
! 133:
! 134: #include "gc.h"
! 135:
! 136: #ifndef THINK_CPLUS
! 137: #define _cdecl
! 138: #endif
! 139:
! 140: #if ! defined( OPERATOR_NEW_ARRAY ) \
! 141: && (__BORLANDC__ >= 0x450 || (__GNUC__ >= 2 && __GNUC_MINOR__ >= 6) \
! 142: || __WATCOMC__ >= 1050 || _MSC_VER >= 1100)
! 143: # define OPERATOR_NEW_ARRAY
! 144: #endif
! 145:
! 146: enum GCPlacement {UseGC,
! 147: #ifndef GC_NAME_CONFLICT
! 148: GC=UseGC,
! 149: #endif
! 150: NoGC, PointerFreeGC};
! 151:
! 152: class gc {public:
! 153: inline void* operator new( size_t size );
! 154: inline void* operator new( size_t size, GCPlacement gcp );
! 155: inline void operator delete( void* obj );
! 156:
! 157: #ifdef OPERATOR_NEW_ARRAY
! 158: inline void* operator new[]( size_t size );
! 159: inline void* operator new[]( size_t size, GCPlacement gcp );
! 160: inline void operator delete[]( void* obj );
! 161: #endif /* OPERATOR_NEW_ARRAY */
! 162: };
! 163: /*
! 164: Instances of classes derived from "gc" will be allocated in the
! 165: collected heap by default, unless an explicit NoGC placement is
! 166: specified. */
! 167:
! 168: class gc_cleanup: virtual public gc {public:
! 169: inline gc_cleanup();
! 170: inline virtual ~gc_cleanup();
! 171: private:
! 172: inline static void _cdecl cleanup( void* obj, void* clientData );};
! 173: /*
! 174: Instances of classes derived from "gc_cleanup" will be allocated
! 175: in the collected heap by default. When the collector discovers an
! 176: inaccessible object derived from "gc_cleanup" or containing a
! 177: member derived from "gc_cleanup", its destructors will be
! 178: invoked. */
! 179:
! 180: extern "C" {typedef void (*GCCleanUpFunc)( void* obj, void* clientData );}
! 181:
! 182: inline void* operator new(
! 183: size_t size,
! 184: GCPlacement gcp,
! 185: GCCleanUpFunc cleanup = 0,
! 186: void* clientData = 0 );
! 187: /*
! 188: Allocates a collectable or uncollected object, according to the
! 189: value of "gcp".
! 190:
! 191: For collectable objects, if "cleanup" is non-null, then when the
! 192: allocated object "obj" becomes inaccessible, the collector will
! 193: invoke the function "cleanup( obj, clientData )" but will not
! 194: invoke the object's destructors. It is an error to explicitly
! 195: delete an object allocated with a non-null "cleanup".
! 196:
! 197: It is an error to specify a non-null "cleanup" with NoGC or for
! 198: classes derived from "gc_cleanup" or containing members derived
! 199: from "gc_cleanup". */
! 200:
! 201: #ifdef OPERATOR_NEW_ARRAY
! 202:
! 203: #ifdef _MSC_VER
! 204: /** This ensures that the system default operator new[] doesn't get
! 205: * undefined, which is what seems to happen on VC++ 6 for some reason
! 206: * if we define a multi-argument operator new[].
! 207: */
! 208: inline void *operator new[]( size_t size )
! 209: {
! 210: return ::operator new( size );
! 211: }
! 212: #endif /* _MSC_VER */
! 213:
! 214: inline void* operator new[](
! 215: size_t size,
! 216: GCPlacement gcp,
! 217: GCCleanUpFunc cleanup = 0,
! 218: void* clientData = 0 );
! 219: /*
! 220: The operator new for arrays, identical to the above. */
! 221:
! 222: #endif /* OPERATOR_NEW_ARRAY */
! 223:
! 224: /****************************************************************************
! 225:
! 226: Inline implementation
! 227:
! 228: ****************************************************************************/
! 229:
! 230: inline void* gc::operator new( size_t size ) {
! 231: return GC_MALLOC( size );}
! 232:
! 233: inline void* gc::operator new( size_t size, GCPlacement gcp ) {
! 234: if (gcp == UseGC)
! 235: return GC_MALLOC( size );
! 236: else if (gcp == PointerFreeGC)
! 237: return GC_MALLOC_ATOMIC( size );
! 238: else
! 239: return GC_MALLOC_UNCOLLECTABLE( size );}
! 240:
! 241: inline void gc::operator delete( void* obj ) {
! 242: GC_FREE( obj );}
! 243:
! 244:
! 245: #ifdef OPERATOR_NEW_ARRAY
! 246:
! 247: inline void* gc::operator new[]( size_t size ) {
! 248: return gc::operator new( size );}
! 249:
! 250: inline void* gc::operator new[]( size_t size, GCPlacement gcp ) {
! 251: return gc::operator new( size, gcp );}
! 252:
! 253: inline void gc::operator delete[]( void* obj ) {
! 254: gc::operator delete( obj );}
! 255:
! 256: #endif /* OPERATOR_NEW_ARRAY */
! 257:
! 258:
! 259: inline gc_cleanup::~gc_cleanup() {
! 260: GC_REGISTER_FINALIZER_IGNORE_SELF( GC_base(this), 0, 0, 0, 0 );}
! 261:
! 262: inline void gc_cleanup::cleanup( void* obj, void* displ ) {
! 263: ((gc_cleanup*) ((char*) obj + (ptrdiff_t) displ))->~gc_cleanup();}
! 264:
! 265: inline gc_cleanup::gc_cleanup() {
! 266: GC_finalization_proc oldProc;
! 267: void* oldData;
! 268: void* base = GC_base( (void *) this );
! 269: if (0 != base) {
! 270: GC_REGISTER_FINALIZER_IGNORE_SELF(
! 271: base, (GC_finalization_proc)cleanup, (void*) ((char*) this - (char*) base),
! 272: &oldProc, &oldData );
! 273: if (0 != oldProc) {
! 274: GC_REGISTER_FINALIZER_IGNORE_SELF( base, oldProc, oldData, 0, 0 );}}}
! 275:
! 276: inline void* operator new(
! 277: size_t size,
! 278: GCPlacement gcp,
! 279: GCCleanUpFunc cleanup,
! 280: void* clientData )
! 281: {
! 282: void* obj;
! 283:
! 284: if (gcp == UseGC) {
! 285: obj = GC_MALLOC( size );
! 286: if (cleanup != 0)
! 287: GC_REGISTER_FINALIZER_IGNORE_SELF(
! 288: obj, cleanup, clientData, 0, 0 );}
! 289: else if (gcp == PointerFreeGC) {
! 290: obj = GC_MALLOC_ATOMIC( size );}
! 291: else {
! 292: obj = GC_MALLOC_UNCOLLECTABLE( size );};
! 293: return obj;}
! 294:
! 295:
! 296: #ifdef OPERATOR_NEW_ARRAY
! 297:
! 298: inline void* operator new[](
! 299: size_t size,
! 300: GCPlacement gcp,
! 301: GCCleanUpFunc cleanup,
! 302: void* clientData )
! 303: {
! 304: return ::operator new( size, gcp, cleanup, clientData );}
! 305:
! 306: #endif /* OPERATOR_NEW_ARRAY */
! 307:
! 308:
! 309: #endif /* GC_CPP_H */
! 310:
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