Annotation of OpenXM_contrib2/asir2000/gc/gc_cpp.h, Revision 1.1.1.1
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: 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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