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gc/include/gc_cpp.h

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+#ifndef GC_CPP_H
+#define GC_CPP_H
+/****************************************************************************
+Copyright (c) 1994 by Xerox Corporation.  All rights reserved.
+ 
+THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
+OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
+ 
+Permission is hereby granted to use or copy this program for any
+purpose, provided the above notices are retained on all copies.
+Permission to modify the code and to distribute modified code is
+granted, provided the above notices are retained, and a notice that
+the code was modified is included with the above copyright notice.
+****************************************************************************
+
+C++ Interface to the Boehm Collector
+
+    John R. Ellis and Jesse Hull 
+    Last modified on Mon Jul 24 15:43:42 PDT 1995 by ellis
+
+This interface provides access to the Boehm collector.  It provides
+basic facilities similar to those described in "Safe, Efficient
+Garbage Collection for C++", by John R. Elis and David L. Detlefs
+(ftp.parc.xerox.com:/pub/ellis/gc).
+
+All heap-allocated objects are either "collectable" or
+"uncollectable".  Programs must explicitly delete uncollectable
+objects, whereas the garbage collector will automatically delete
+collectable objects when it discovers them to be inaccessible.
+Collectable objects may freely point at uncollectable objects and vice
+versa.
+
+Objects allocated with the built-in "::operator new" are uncollectable.
+
+Objects derived from class "gc" are collectable.  For example:
+
+    class A: public gc {...};
+    A* a = new A;       // a is collectable. 
+
+Collectable instances of non-class types can be allocated using the GC
+placement:
+
+    typedef int A[ 10 ];
+    A* a = new (GC) A;
+
+Uncollectable instances of classes derived from "gc" can be allocated
+using the NoGC placement:
+
+    class A: public gc {...};
+    A* a = new (NoGC) A;   // a is uncollectable.
+
+Both uncollectable and collectable objects can be explicitly deleted
+with "delete", which invokes an object's destructors and frees its
+storage immediately.
+
+A collectable object may have a clean-up function, which will be
+invoked when the collector discovers the object to be inaccessible.
+An object derived from "gc_cleanup" or containing a member derived
+from "gc_cleanup" has a default clean-up function that invokes the
+object's destructors.  Explicit clean-up functions may be specified as
+an additional placement argument:
+
+    A* a = ::new (GC, MyCleanup) A;
+
+An object is considered "accessible" by the collector if it can be
+reached by a path of pointers from static variables, automatic
+variables of active functions, or from some object with clean-up
+enabled; pointers from an object to itself are ignored.
+
+Thus, if objects A and B both have clean-up functions, and A points at
+B, B is considered accessible.  After A's clean-up is invoked and its
+storage released, B will then become inaccessible and will have its
+clean-up invoked.  If A points at B and B points to A, forming a
+cycle, then that's considered a storage leak, and neither will be
+collectable.  See the interface gc.h for low-level facilities for
+handling such cycles of objects with clean-up.
+
+The collector cannot guarrantee that it will find all inaccessible
+objects.  In practice, it finds almost all of them.
+
+
+Cautions:
+
+1. Be sure the collector has been augmented with "make c++".
+
+2.  If your compiler supports the new "operator new[]" syntax, then
+add -DOPERATOR_NEW_ARRAY to the Makefile.
+
+If your compiler doesn't support "operator new[]", beware that an
+array of type T, where T is derived from "gc", may or may not be
+allocated as a collectable object (it depends on the compiler).  Use
+the explicit GC placement to make the array collectable.  For example:
+
+    class A: public gc {...};
+    A* a1 = new A[ 10 ];        // collectable or uncollectable?
+    A* a2 = new (GC) A[ 10 ];   // collectable
+
+3. The destructors of collectable arrays of objects derived from
+"gc_cleanup" will not be invoked properly.  For example:
+
+    class A: public gc_cleanup {...};
+    A* a = new (GC) A[ 10 ];    // destructors not invoked correctly
+
+Typically, only the destructor for the first element of the array will
+be invoked when the array is garbage-collected.  To get all the
+destructors of any array executed, you must supply an explicit
+clean-up function:
+
+    A* a = new (GC, MyCleanUp) A[ 10 ];
+
+(Implementing clean-up of arrays correctly, portably, and in a way
+that preserves the correct exception semantics requires a language
+extension, e.g. the "gc" keyword.)
+
+4. Compiler bugs:
+
+* Solaris 2's CC (SC3.0) doesn't implement t->~T() correctly, so the
+destructors of classes derived from gc_cleanup won't be invoked.
+You'll have to explicitly register a clean-up function with
+new-placement syntax.
+
+* Evidently cfront 3.0 does not allow destructors to be explicitly
+invoked using the ANSI-conforming syntax t->~T().  If you're using
+cfront 3.0, you'll have to comment out the class gc_cleanup, which
+uses explicit invocation.
+
+****************************************************************************/
+
+#include "gc.h"
+
+#ifndef THINK_CPLUS
+#define _cdecl
+#endif
+
+#if ! defined( OPERATOR_NEW_ARRAY ) \
+    && (__BORLANDC__ >= 0x450 || (__GNUC__ >= 2 && __GNUC_MINOR__ >= 6) \
+        || __WATCOMC__ >= 1050)
+#   define OPERATOR_NEW_ARRAY
+#endif
+
+enum GCPlacement {GC, NoGC, PointerFreeGC};
+
+class gc {public:
+    inline void* operator new( size_t size );
+    inline void* operator new( size_t size, GCPlacement gcp );
+    inline void operator delete( void* obj );
+
+#ifdef OPERATOR_NEW_ARRAY
+    inline void* operator new[]( size_t size );
+    inline void* operator new[]( size_t size, GCPlacement gcp );
+    inline void operator delete[]( void* obj );
+#endif /* OPERATOR_NEW_ARRAY */
+    };    
+    /*
+    Instances of classes derived from "gc" will be allocated in the 
+    collected heap by default, unless an explicit NoGC placement is
+    specified. */
+
+class gc_cleanup: virtual public gc {public:
+    inline gc_cleanup();
+    inline virtual ~gc_cleanup();
+private:
+    inline static void _cdecl cleanup( void* obj, void* clientData );};
+    /*
+    Instances of classes derived from "gc_cleanup" will be allocated
+    in the collected heap by default.  When the collector discovers an
+    inaccessible object derived from "gc_cleanup" or containing a
+    member derived from "gc_cleanup", its destructors will be
+    invoked. */
+
+extern "C" {typedef void (*GCCleanUpFunc)( void* obj, void* clientData );}
+
+inline void* operator new( 
+    size_t size, 
+    GCPlacement gcp,
+    GCCleanUpFunc cleanup = 0,
+    void* clientData = 0 );
+    /*
+    Allocates a collectable or uncollected object, according to the
+    value of "gcp".
+
+    For collectable objects, if "cleanup" is non-null, then when the
+    allocated object "obj" becomes inaccessible, the collector will
+    invoke the function "cleanup( obj, clientData )" but will not
+    invoke the object's destructors.  It is an error to explicitly
+    delete an object allocated with a non-null "cleanup".
+
+    It is an error to specify a non-null "cleanup" with NoGC or for
+    classes derived from "gc_cleanup" or containing members derived
+    from "gc_cleanup". */
+
+#ifdef OPERATOR_NEW_ARRAY
+
+inline void* operator new[](
+    size_t size, 
+    GCPlacement gcp,
+    GCCleanUpFunc cleanup = 0,
+    void* clientData = 0 );
+    /*
+    The operator new for arrays, identical to the above. */
+
+#endif /* OPERATOR_NEW_ARRAY */
+
+/****************************************************************************
+
+Inline implementation
+
+****************************************************************************/
+
+inline void* gc::operator new( size_t size ) {
+    return GC_MALLOC( size );}
+    
+inline void* gc::operator new( size_t size, GCPlacement gcp ) {
+    if (gcp == GC) 
+        return GC_MALLOC( size );
+    else if (gcp == PointerFreeGC)
+	return GC_MALLOC_ATOMIC( size );
+    else
+        return GC_MALLOC_UNCOLLECTABLE( size );}
+
+inline void gc::operator delete( void* obj ) {
+    GC_FREE( obj );}
+    
+
+#ifdef OPERATOR_NEW_ARRAY
+
+inline void* gc::operator new[]( size_t size ) {
+    return gc::operator new( size );}
+    
+inline void* gc::operator new[]( size_t size, GCPlacement gcp ) {
+    return gc::operator new( size, gcp );}
+
+inline void gc::operator delete[]( void* obj ) {
+    gc::operator delete( obj );}
+    
+#endif /* OPERATOR_NEW_ARRAY */
+
+
+inline gc_cleanup::~gc_cleanup() {
+    GC_REGISTER_FINALIZER_IGNORE_SELF( GC_base(this), 0, 0, 0, 0 );}
+
+inline void gc_cleanup::cleanup( void* obj, void* displ ) {
+    ((gc_cleanup*) ((char*) obj + (ptrdiff_t) displ))->~gc_cleanup();}
+
+inline gc_cleanup::gc_cleanup() {
+    GC_finalization_proc oldProc;
+    void* oldData;
+    void* base = GC_base( (void *) this );
+    if (0 == base) return;
+    GC_REGISTER_FINALIZER_IGNORE_SELF( 
+        base, cleanup, (void*) ((char*) this - (char*) base), 
+        &oldProc, &oldData );
+    if (0 != oldProc) {
+        GC_REGISTER_FINALIZER_IGNORE_SELF( base, oldProc, oldData, 0, 0 );}}
+
+inline void* operator new( 
+    size_t size, 
+    GCPlacement gcp,
+    GCCleanUpFunc cleanup,
+    void* clientData )
+{
+    void* obj;
+
+    if (gcp == GC) {
+        obj = GC_MALLOC( size );
+        if (cleanup != 0) 
+            GC_REGISTER_FINALIZER_IGNORE_SELF( 
+                obj, cleanup, clientData, 0, 0 );}
+    else if (gcp == PointerFreeGC) {
+        obj = GC_MALLOC_ATOMIC( size );}
+    else {
+        obj = GC_MALLOC_UNCOLLECTABLE( size );};
+    return obj;}
+        
+
+#ifdef OPERATOR_NEW_ARRAY
+
+inline void* operator new[]( 
+    size_t size, 
+    GCPlacement gcp,
+    GCCleanUpFunc cleanup,
+    void* clientData )
+{
+    return ::operator new( size, gcp, cleanup, clientData );}
+
+#endif /* OPERATOR_NEW_ARRAY */
+
+
+#endif /* GC_CPP_H */
+