+++ /dev/null
-/***************************************************************************
-
-Interface between g++ and Boehm GC
-
- Copyright (c) 1991-1995 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 copy this code for any purpose,
- provided the above notices are retained on all copies.
-
- Last modified on Sun Jul 16 23:21:14 PDT 1995 by ellis
-
-This module provides runtime support for implementing the
-Ellis/Detlefs GC proposal, "Safe, Efficient Garbage Collection for
-C++", within g++, using its -fgc-keyword extension. It defines
-versions of __builtin_new, __builtin_new_gc, __builtin_vec_new,
-__builtin_vec_new_gc, __builtin_delete, and __builtin_vec_delete that
-invoke the Bohem GC. It also implements the WeakPointer.h interface.
-
-This module assumes the following configuration options of the Boehm GC:
-
- -DALL_INTERIOR_POINTERS
- -DDONT_ADD_BYTE_AT_END
-
-This module adds its own required padding to the end of objects to
-support C/C++ "one-past-the-object" pointer semantics.
-
-****************************************************************************/
-
-#include <stddef.h>
-#include "gc.h"
-
-#if defined(__STDC__)
-# define PROTO( args ) args
-#else
-# define PROTO( args ) ()
-# endif
-
-#define BITSPERBYTE 8
- /* What's the portable way to do this? */
-
-
-typedef void (*vfp) PROTO(( void ));
-extern vfp __new_handler;
-extern void __default_new_handler PROTO(( void ));
-
-
-/* A destructor_proc is the compiler generated procedure representing a
-C++ destructor. The "flag" argument is a hidden argument following some
-compiler convention. */
-
-typedef (*destructor_proc) PROTO(( void* this, int flag ));
-
-
-/***************************************************************************
-
-A BI_header is the header the compiler adds to the front of
-new-allocated arrays of objects with destructors. The header is
-padded out to a double, because that's what the compiler does to
-ensure proper alignment of array elements on some architectures.
-
-int NUM_ARRAY_ELEMENTS (void* o)
- returns the number of array elements for array object o.
-
-char* FIRST_ELEMENT_P (void* o)
- returns the address of the first element of array object o.
-
-***************************************************************************/
-
-typedef struct BI_header {
- int nelts;
- char padding [sizeof( double ) - sizeof( int )];
- /* Better way to do this? */
-} BI_header;
-
-#define NUM_ARRAY_ELEMENTS( o ) \
- (((BI_header*) o)->nelts)
-
-#define FIRST_ELEMENT_P( o ) \
- ((char*) o + sizeof( BI_header ))
-
-
-/***************************************************************************
-
-The __builtin_new routines add a descriptor word to the end of each
-object. The descriptor serves two purposes.
-
-First, the descriptor acts as padding, implementing C/C++ pointer
-semantics. C and C++ allow a valid array pointer to be incremented
-one past the end of an object. The extra padding ensures that the
-collector will recognize that such a pointer points to the object and
-not the next object in memory.
-
-Second, the descriptor stores three extra pieces of information,
-whether an object has a registered finalizer (destructor), whether it
-may have any weak pointers referencing it, and for collectible arrays,
-the element size of the array. The element size is required for the
-array's finalizer to iterate through the elements of the array. (An
-alternative design would have the compiler generate a finalizer
-procedure for each different array type. But given the overhead of
-finalization, there isn't any efficiency to be gained by that.)
-
-The descriptor must be added to non-collectible as well as collectible
-objects, since the Ellis/Detlefs proposal allows "pointer to gc T" to
-be assigned to a "pointer to T", which could then be deleted. Thus,
-__builtin_delete must determine at runtime whether an object is
-collectible, whether it has weak pointers referencing it, and whether
-it may have a finalizer that needs unregistering. Though
-GC_REGISTER_FINALIZER doesn't care if you ask it to unregister a
-finalizer for an object that doesn't have one, it is a non-trivial
-procedure that does a hash look-up, etc. The descriptor trades a
-little extra space for a significant increase in time on the fast path
-through delete. (A similar argument applies to
-GC_UNREGISTER_DISAPPEARING_LINK).
-
-For non-array types, the space for the descriptor could be shrunk to a
-single byte for storing the "has finalizer" flag. But this would save
-space only on arrays of char (whose size is not a multiple of the word
-size) and structs whose largest member is less than a word in size
-(very infrequent). And it would require that programmers actually
-remember to call "delete[]" instead of "delete" (which they should,
-but there are probably lots of buggy programs out there). For the
-moment, the space savings seems not worthwhile, especially considering
-that the Boehm GC is already quite space competitive with other
-malloc's.
-
-
-Given a pointer o to the base of an object:
-
-Descriptor* DESCRIPTOR (void* o)
- returns a pointer to the descriptor for o.
-
-The implementation of descriptors relies on the fact that the GC
-implementation allocates objects in units of the machine's natural
-word size (e.g. 32 bits on a SPARC, 64 bits on an Alpha).
-
-**************************************************************************/
-
-typedef struct Descriptor {
- unsigned has_weak_pointers: 1;
- unsigned has_finalizer: 1;
- unsigned element_size: BITSPERBYTE * sizeof( unsigned ) - 2;
-} Descriptor;
-
-#define DESCRIPTOR( o ) \
- ((Descriptor*) ((char*)(o) + GC_size( o ) - sizeof( Descriptor )))
-
-
-/**************************************************************************
-
-Implementations of global operator new() and operator delete()
-
-***************************************************************************/
-
-
-void* __builtin_new( size )
- size_t size;
- /*
- For non-gc non-array types, the compiler generates calls to
- __builtin_new, which allocates non-collected storage via
- GC_MALLOC_UNCOLLECTABLE. This ensures that the non-collected
- storage will be part of the collector's root set, required by the
- Ellis/Detlefs semantics. */
-{
- vfp handler = __new_handler ? __new_handler : __default_new_handler;
-
- while (1) {
- void* o = GC_MALLOC_UNCOLLECTABLE( size + sizeof( Descriptor ) );
- if (o != 0) return o;
- (*handler) ();}}
-
-
-void* __builtin_vec_new( size )
- size_t size;
- /*
- For non-gc array types, the compiler generates calls to
- __builtin_vec_new. */
-{
- return __builtin_new( size );}
-
-
-void* __builtin_new_gc( size )
- size_t size;
- /*
- For gc non-array types, the compiler generates calls to
- __builtin_new_gc, which allocates collected storage via
- GC_MALLOC. */
-{
- vfp handler = __new_handler ? __new_handler : __default_new_handler;
-
- while (1) {
- void* o = GC_MALLOC( size + sizeof( Descriptor ) );
- if (o != 0) return o;
- (*handler) ();}}
-
-
-void* __builtin_new_gc_a( size )
- size_t size;
- /*
- For non-pointer-containing gc non-array types, the compiler
- generates calls to __builtin_new_gc_a, which allocates collected
- storage via GC_MALLOC_ATOMIC. */
-{
- vfp handler = __new_handler ? __new_handler : __default_new_handler;
-
- while (1) {
- void* o = GC_MALLOC_ATOMIC( size + sizeof( Descriptor ) );
- if (o != 0) return o;
- (*handler) ();}}
-
-
-void* __builtin_vec_new_gc( size )
- size_t size;
- /*
- For gc array types, the compiler generates calls to
- __builtin_vec_new_gc. */
-{
- return __builtin_new_gc( size );}
-
-
-void* __builtin_vec_new_gc_a( size )
- size_t size;
- /*
- For non-pointer-containing gc array types, the compiler generates
- calls to __builtin_vec_new_gc_a. */
-{
- return __builtin_new_gc_a( size );}
-
-
-static void call_destructor( o, data )
- void* o;
- void* data;
- /*
- call_destructor is the GC finalizer proc registered for non-array
- gc objects with destructors. Its client data is the destructor
- proc, which it calls with the magic integer 2, a special flag
- obeying the compiler convention for destructors. */
-{
- ((destructor_proc) data)( o, 2 );}
-
-
-void* __builtin_new_gc_dtor( o, d )
- void* o;
- destructor_proc d;
- /*
- The compiler generates a call to __builtin_new_gc_dtor to register
- the destructor "d" of a non-array gc object "o" as a GC finalizer.
- The destructor is registered via
- GC_REGISTER_FINALIZER_IGNORE_SELF, which causes the collector to
- ignore pointers from the object to itself when determining when
- the object can be finalized. This is necessary due to the self
- pointers used in the internal representation of multiply-inherited
- objects. */
-{
- Descriptor* desc = DESCRIPTOR( o );
-
- GC_REGISTER_FINALIZER_IGNORE_SELF( o, call_destructor, d, 0, 0 );
- desc->has_finalizer = 1;}
-
-
-static void call_array_destructor( o, data )
- void* o;
- void* data;
- /*
- call_array_destructor is the GC finalizer proc registered for gc
- array objects whose elements have destructors. Its client data is
- the destructor proc. It iterates through the elements of the
- array in reverse order, calling the destructor on each. */
-{
- int num = NUM_ARRAY_ELEMENTS( o );
- Descriptor* desc = DESCRIPTOR( o );
- size_t size = desc->element_size;
- char* first_p = FIRST_ELEMENT_P( o );
- char* p = first_p + (num - 1) * size;
-
- if (num > 0) {
- while (1) {
- ((destructor_proc) data)( p, 2 );
- if (p == first_p) break;
- p -= size;}}}
-
-
-void* __builtin_vec_new_gc_dtor( first_elem, d, element_size )
- void* first_elem;
- destructor_proc d;
- size_t element_size;
- /*
- The compiler generates a call to __builtin_vec_new_gc_dtor to
- register the destructor "d" of a gc array object as a GC
- finalizer. "first_elem" points to the first element of the array,
- *not* the beginning of the object (this makes the generated call
- to this function smaller). The elements of the array are of size
- "element_size". The destructor is registered as in
- _builtin_new_gc_dtor. */
-{
- void* o = (char*) first_elem - sizeof( BI_header );
- Descriptor* desc = DESCRIPTOR( o );
-
- GC_REGISTER_FINALIZER_IGNORE_SELF( o, call_array_destructor, d, 0, 0 );
- desc->element_size = element_size;
- desc->has_finalizer = 1;}
-
-
-void __builtin_delete( o )
- void* o;
- /*
- The compiler generates calls to __builtin_delete for operator
- delete(). The GC currently requires that any registered
- finalizers be unregistered before explicitly freeing an object.
- If the object has any weak pointers referencing it, we can't
- actually free it now. */
-{
- if (o != 0) {
- Descriptor* desc = DESCRIPTOR( o );
- if (desc->has_finalizer) GC_REGISTER_FINALIZER( o, 0, 0, 0, 0 );
- if (! desc->has_weak_pointers) GC_FREE( o );}}
-
-
-void __builtin_vec_delete( o )
- void* o;
- /*
- The compiler generates calls to __builitn_vec_delete for operator
- delete[](). */
-{
- __builtin_delete( o );}
-
-
-/**************************************************************************
-
-Implementations of the template class WeakPointer from WeakPointer.h
-
-***************************************************************************/
-
-typedef struct WeakPointer {
- void* pointer;
-} WeakPointer;
-
-
-void* _WeakPointer_New( t )
- void* t;
-{
- if (t == 0) {
- return 0;}
- else {
- void* base = GC_base( t );
- WeakPointer* wp =
- (WeakPointer*) GC_MALLOC_ATOMIC( sizeof( WeakPointer ) );
- Descriptor* desc = DESCRIPTOR( base );
-
- wp->pointer = t;
- desc->has_weak_pointers = 1;
- GC_general_register_disappearing_link( &wp->pointer, base );
- return wp;}}
-
-
-static void* PointerWithLock( wp )
- WeakPointer* wp;
-{
- if (wp == 0 || wp->pointer == 0) {
- return 0;}
- else {
- return (void*) wp->pointer;}}
-
-
-void* _WeakPointer_Pointer( wp )
- WeakPointer* wp;
-{
- return (void*) GC_call_with_alloc_lock( PointerWithLock, wp );}
-
-
-typedef struct EqualClosure {
- WeakPointer* wp1;
- WeakPointer* wp2;
-} EqualClosure;
-
-
-static void* EqualWithLock( ec )
- EqualClosure* ec;
-{
- if (ec->wp1 == 0 || ec->wp2 == 0) {
- return (void*) (ec->wp1 == ec->wp2);}
- else {
- return (void*) (ec->wp1->pointer == ec->wp2->pointer);}}
-
-
-int _WeakPointer_Equal( wp1, wp2 )
- WeakPointer* wp1;
- WeakPointer* wp2;
-{
- EqualClosure ec;
-
- ec.wp1 = wp1;
- ec.wp2 = wp2;
- return (int) GC_call_with_alloc_lock( EqualWithLock, &ec );}
-
-
-int _WeakPointer_Hash( wp )
- WeakPointer* wp;
-{
- return (int) _WeakPointer_Pointer( wp );}
-
-
-/**************************************************************************
-
-Implementations of the template class CleanUp from WeakPointer.h
-
-***************************************************************************/
-
-typedef struct Closure {
- void (*c) PROTO(( void* d, void* t ));
- ptrdiff_t t_offset;
- void* d;
-} Closure;
-
-
-static void _CleanUp_CallClosure( obj, data )
- void* obj;
- void* data;
-{
- Closure* closure = (Closure*) data;
- closure->c( closure->d, (char*) obj + closure->t_offset );}
-
-
-void _CleanUp_Set( t, c, d )
- void* t;
- void (*c) PROTO(( void* d, void* t ));
- void* d;
-{
- void* base = GC_base( t );
- Descriptor* desc = DESCRIPTOR( t );
-
- if (c == 0) {
- GC_REGISTER_FINALIZER_IGNORE_SELF( base, 0, 0, 0, 0 );
- desc->has_finalizer = 0;}
- else {
- Closure* closure = (Closure*) GC_MALLOC( sizeof( Closure ) );
- closure->c = c;
- closure->t_offset = (char*) t - (char*) base;
- closure->d = d;
- GC_REGISTER_FINALIZER_IGNORE_SELF( base, _CleanUp_CallClosure,
- closure, 0, 0 );
- desc->has_finalizer = 1;}}
-
-
-void _CleanUp_Call( t )
- void* t;
-{
- /* ? Aren't we supposed to deactivate weak pointers to t too?
- Why? */
- void* base = GC_base( t );
- void* d;
- GC_finalization_proc f;
-
- GC_REGISTER_FINALIZER( base, 0, 0, &f, &d );
- f( base, d );}
-
-
-typedef struct QueueElem {
- void* o;
- GC_finalization_proc f;
- void* d;
- struct QueueElem* next;
-} QueueElem;
-
-
-void* _CleanUp_Queue_NewHead()
-{
- return GC_MALLOC( sizeof( QueueElem ) );}
-
-
-static void _CleanUp_Queue_Enqueue( obj, data )
- void* obj;
- void* data;
-{
- QueueElem* q = (QueueElem*) data;
- QueueElem* head = q->next;
-
- q->o = obj;
- q->next = head->next;
- head->next = q;}
-
-
-void _CleanUp_Queue_Set( h, t )
- void* h;
- void* t;
-{
- QueueElem* head = (QueueElem*) h;
- void* base = GC_base( t );
- void* d;
- GC_finalization_proc f;
- QueueElem* q = (QueueElem*) GC_MALLOC( sizeof( QueueElem ) );
-
- GC_REGISTER_FINALIZER( base, _CleanUp_Queue_Enqueue, q, &f, &d );
- q->f = f;
- q->d = d;
- q->next = head;}
-
-
-int _CleanUp_Queue_Call( h )
- void* h;
-{
- QueueElem* head = (QueueElem*) h;
- QueueElem* q = head->next;
-
- if (q == 0) {
- return 0;}
- else {
- head->next = q->next;
- q->next = 0;
- if (q->f != 0) q->f( q->o, q->d );
- return 1;}}
-
-
-
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