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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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