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xo-alloc: + comments on design

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Roland Conybeare 2025-12-04 17:29:27 -05:00
commit 676a9d0d62
1 changed files with 15 additions and 9 deletions
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24
include/xo/alloc/Object.hpp
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@ -20,14 +20,18 @@ namespace xo {
/** Root class for all xo GC-collectable objects.
*
* Design note:
*
* relying on inheritance means we insist that GC traits
* for a type appear directly in that type's vtable, and at specific locations.
* This implies one level of indirection when GC traverses an instance.
*
* Would be feasible to relax the must-inherit-from-Object constraint
* by having GC use its own wrapper, at cost of an extra layer of indirection
* Design notes:
* 1. xo::IObject -> xo-allocutil header-only library
* xo::Object -> xo-alloc ordinary library
* 2. relying on inheritance means we insist that GC traits
* for a type appear directly in that type's vtable, and at specific locations.
* This implies one level of indirection when GC traverses an instance.
* 3. Could adapt a gc-aware XO library (such as xo-ordinaltree)
* to a non-xo garbage collector.
* Would still need to use xo::IObject and xo::gc::gc_allocator_traits,
* but not necessarily xo::Object
* 4. Would be feasible to relax the must-inherit-from-Object constraint
* by having GC use its own wrapper, at cost of an extra layer of indirection
**/
class Object : public IObject {
public:
@ -49,7 +53,9 @@ namespace xo {
/** assign value @p rhs to member @p *lhs of @p parent.
* if assignment creates a cross-generational or cross-checkpoint pointer,
* add mutation log entry
* add mutation log entry.
*
* DEPRECATED. prefer IObject::_gc_assign_member, for explicit alloc
**/
template <typename T>
static void assign_member(gp<IObject> parent, gp<T> * lhs, gp<IObject> rhs);