Annotation of OpenXM_contrib2/asir2000/gc/include/gc_cpp.h, Revision 1.2
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
1.2 ! noro 23: (ftp://ftp.parc.xerox.com/pub/ellis/gc).
1.1 noro 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
1.2 ! noro 40: (or UseGC) placement:
1.1 noro 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:
1.2 ! noro 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:
1.1 noro 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) \
1.2 ! noro 142: || __WATCOMC__ >= 1050 || _MSC_VER >= 1100)
1.1 noro 143: # define OPERATOR_NEW_ARRAY
144: #endif
145:
1.2 ! noro 146: enum GCPlacement {UseGC,
! 147: #ifndef GC_NAME_CONFLICT
! 148: GC=UseGC,
! 149: #endif
! 150: NoGC, PointerFreeGC};
1.1 noro 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:
1.2 ! noro 182: #ifdef _MSC_VER
! 183: // Disable warning that "no matching operator delete found; memory will
! 184: // not be freed if initialization throws an exception"
! 185: # pragma warning(disable:4291)
! 186: #endif
! 187:
1.1 noro 188: inline void* operator new(
189: size_t size,
190: GCPlacement gcp,
191: GCCleanUpFunc cleanup = 0,
192: void* clientData = 0 );
193: /*
194: Allocates a collectable or uncollected object, according to the
195: value of "gcp".
196:
197: For collectable objects, if "cleanup" is non-null, then when the
198: allocated object "obj" becomes inaccessible, the collector will
199: invoke the function "cleanup( obj, clientData )" but will not
200: invoke the object's destructors. It is an error to explicitly
201: delete an object allocated with a non-null "cleanup".
202:
203: It is an error to specify a non-null "cleanup" with NoGC or for
204: classes derived from "gc_cleanup" or containing members derived
205: from "gc_cleanup". */
206:
207: #ifdef OPERATOR_NEW_ARRAY
208:
1.2 ! noro 209: #ifdef _MSC_VER
! 210: /** This ensures that the system default operator new[] doesn't get
! 211: * undefined, which is what seems to happen on VC++ 6 for some reason
! 212: * if we define a multi-argument operator new[].
! 213: * There seems to be really redirect new in this environment without
! 214: * including this everywhere.
! 215: */
! 216: inline void *operator new[]( size_t size )
! 217: {
! 218: return GC_MALLOC_UNCOLLECTABLE( size );
! 219: }
! 220:
! 221: inline void operator delete[](void* obj)
! 222: {
! 223: GC_FREE(obj);
! 224: };
! 225:
! 226: inline void* operator new( size_t size)
! 227: {
! 228: return GC_MALLOC_UNCOLLECTABLE( size);
! 229: };
! 230:
! 231: inline void operator delete(void* obj)
! 232: {
! 233: GC_FREE(obj);
! 234: };
! 235:
! 236:
! 237: // This new operator is used by VC++ in case of Debug builds !
! 238: inline void* operator new( size_t size,
! 239: int ,//nBlockUse,
! 240: const char * szFileName,
! 241: int nLine
! 242: ) {
! 243: # ifndef GC_DEBUG
! 244: return GC_malloc_uncollectable( size );
! 245: # else
! 246: return GC_debug_malloc_uncollectable(size, szFileName, nLine);
! 247: # endif
! 248: }
! 249:
! 250: #endif /* _MSC_VER */
! 251:
1.1 noro 252: inline void* operator new[](
253: size_t size,
254: GCPlacement gcp,
255: GCCleanUpFunc cleanup = 0,
256: void* clientData = 0 );
257: /*
258: The operator new for arrays, identical to the above. */
259:
260: #endif /* OPERATOR_NEW_ARRAY */
261:
262: /****************************************************************************
263:
264: Inline implementation
265:
266: ****************************************************************************/
267:
268: inline void* gc::operator new( size_t size ) {
269: return GC_MALLOC( size );}
270:
271: inline void* gc::operator new( size_t size, GCPlacement gcp ) {
1.2 ! noro 272: if (gcp == UseGC)
1.1 noro 273: return GC_MALLOC( size );
274: else if (gcp == PointerFreeGC)
275: return GC_MALLOC_ATOMIC( size );
276: else
277: return GC_MALLOC_UNCOLLECTABLE( size );}
278:
279: inline void gc::operator delete( void* obj ) {
280: GC_FREE( obj );}
281:
282:
283: #ifdef OPERATOR_NEW_ARRAY
284:
285: inline void* gc::operator new[]( size_t size ) {
286: return gc::operator new( size );}
287:
288: inline void* gc::operator new[]( size_t size, GCPlacement gcp ) {
289: return gc::operator new( size, gcp );}
290:
291: inline void gc::operator delete[]( void* obj ) {
292: gc::operator delete( obj );}
293:
294: #endif /* OPERATOR_NEW_ARRAY */
295:
296:
297: inline gc_cleanup::~gc_cleanup() {
298: GC_REGISTER_FINALIZER_IGNORE_SELF( GC_base(this), 0, 0, 0, 0 );}
299:
300: inline void gc_cleanup::cleanup( void* obj, void* displ ) {
301: ((gc_cleanup*) ((char*) obj + (ptrdiff_t) displ))->~gc_cleanup();}
302:
303: inline gc_cleanup::gc_cleanup() {
304: GC_finalization_proc oldProc;
305: void* oldData;
306: void* base = GC_base( (void *) this );
1.2 ! noro 307: if (0 != base) {
! 308: GC_REGISTER_FINALIZER_IGNORE_SELF(
! 309: base, (GC_finalization_proc)cleanup, (void*) ((char*) this - (char*) base),
1.1 noro 310: &oldProc, &oldData );
1.2 ! noro 311: if (0 != oldProc) {
! 312: GC_REGISTER_FINALIZER_IGNORE_SELF( base, oldProc, oldData, 0, 0 );}}}
1.1 noro 313:
314: inline void* operator new(
315: size_t size,
316: GCPlacement gcp,
317: GCCleanUpFunc cleanup,
318: void* clientData )
319: {
320: void* obj;
321:
1.2 ! noro 322: if (gcp == UseGC) {
1.1 noro 323: obj = GC_MALLOC( size );
324: if (cleanup != 0)
325: GC_REGISTER_FINALIZER_IGNORE_SELF(
326: obj, cleanup, clientData, 0, 0 );}
327: else if (gcp == PointerFreeGC) {
328: obj = GC_MALLOC_ATOMIC( size );}
329: else {
330: obj = GC_MALLOC_UNCOLLECTABLE( size );};
331: return obj;}
332:
333:
334: #ifdef OPERATOR_NEW_ARRAY
335:
336: inline void* operator new[](
337: size_t size,
338: GCPlacement gcp,
339: GCCleanUpFunc cleanup,
340: void* clientData )
341: {
342: return ::operator new( size, gcp, cleanup, clientData );}
343:
344: #endif /* OPERATOR_NEW_ARRAY */
345:
346:
347: #endif /* GC_CPP_H */
348:
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