CellPtrBase Class Reference

An implementation detail for the type-specific templated cell pointers. More...

#include <CellPtr.h>

Inheritance diagram for CellPtrBase:

Public Member Functions
	operator bool () const noexcept
void	reset () noexcept
auto	cmpPointers (const CellPtrBase &o) const noexcept
	This is exactly like the spaceship operator in C++20.
auto	cmpObjects (const CellPtrBase &o) const noexcept
	This is the spaceship operator acting on pointed-to objects.
auto	cmpObjects (const Observed *o) const noexcept
	This is the spaceship operator acting on pointed-to objects.
bool	IsNull () const
bool	HasOneObserved () const
bool	HasControlBlock () const

Static Public Member Functions
template<typename U >
static bool constexpr	is_pointer ()
static size_t	GetLiveInstanceCount () noexcept

Protected Member Functions
	CellPtrBase (Observed *obj=nullptr) noexcept
	CellPtrBase (const CellPtrBase &o) noexcept
	CellPtrBase (CellPtrBase &&o) noexcept
CellPtrBase &	operator= (const CellPtrBase &o) noexcept
CellPtrBase &	operator= (CellPtrBase &&o) noexcept
Observed *	base_get () const noexcept
void	base_reset (Observed *obj=nullptr) noexcept

Static Protected Member Functions
static int	CmpAddresses (const void *a, const void *b) noexcept
	A total order over two (possibly unrelated) addresses, usable with < 0 / == 0 / > 0. Compares them as unsigned integers rather than via pointer subtraction: see the GH #2208 comment on cmpObjects() below.

Detailed Description

An implementation detail for the type-specific templated cell pointers.

A CellPtrBase (and thus the derived CellPtr) can be in one of 3 states:

1. Pointing to no object: its m_ptr is null.
2. A sole pointer to an object: its m_ptr points to the Observed, and observed's m_ptr points back at this pointer.
3. One of many pointers to the object: its m_ptr points to the Observed::ControlBlock, and the observed's m_ptr also points to the control block.

Member Function Documentation

base_reset()

void CellPtrBase::base_reset ( Observed *  obj = nullptr )

protectednoexcept

Different objects must have control blocks that are either null or non-null but different.

cmpObjects()

auto CellPtrBase::cmpObjects ( const CellPtrBase &  o ) const

inlinenoexcept

This is the spaceship operator acting on pointed-to objects.

GH #2208: this used to be a plain base_get() - o.base_get() pointer subtraction. That is undefined behavior for two pointers into unrelated objects, and in practice, on 32-bit architectures, it can silently produce the wrong sign: a signed ptrdiff_t subtraction of two addresses spread widely across the (much smaller) 32-bit address space can overflow and wrap around, which a 64-bit build's much sparser address space essentially never triggers. Comparing the two addresses as unsigned integers instead is well-defined on any architecture and gives the total order operator< (used via cmpObjects() < 0) actually needs.

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The documentation for this class was generated from the following files:

• src/cells/CellPtr.h
• src/cells/CellPtr.cpp