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Annotation of OpenXM_contrib2/asir2000/gc/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:     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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