Commit eaa3da72 authored by Mark Olesen's avatar Mark Olesen Committed by Andrew Heather
Browse files

ENH: extend size of NullObject for safer reinterpret cast

- previously had a single pointer/value zeros (8 bytes), this meant
  that the reinterpret cast to a List would yield a reference that
  could be unsafe under certain conditions.

  Eg,
     const labelList& myList = labelList::null();

     Info<< myList.size() << nl; // OK since size is the first parameter

     SubList<label>(myList, 0);  // Unsafe

  The SubList usage is unsafe since it passes in pointer and size into
  the underlying UList. However, the pointer from the labelList::null()
  will be whatever happens to be around in memory immediately after the
  NullObject singleton. This is mostly not a problem if the List size
  is always checked, but does mean that the data pointer is rather
  dubious.

- Increase the size of the nullObject singleton to 32 bytes of zeros
  to ensure that most reinterpret casting will not result in objects
  that reference arbitrary memory.

  The 32-byte data size is rather arbitrary, but covers most basic
  containers.
parent 2016f88e
/*---------------------------------------------------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration |
\\ / A nd | Copyright (C) 2019 OpenCFD Ltd.
\\/ M anipulation |
-------------------------------------------------------------------------------
| Copyright (C) 2014 OpenFOAM Foundation
-------------------------------------------------------------------------------
License
This file is part of OpenFOAM.
OpenFOAM is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with OpenFOAM. If not, see <http://www.gnu.org/licenses/>.
Application
Test-nullObject
Description
Tests of nullObject
\*---------------------------------------------------------------------------*/
#include "nullObject.H"
#include "List.H"
#include "HashSet.H"
#include "faceList.H"
#include "pointField.H"
#include "IOstreams.H"
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
using namespace Foam;
class SimpleClass
{
public:
//- Null constructor
......@@ -14,6 +52,26 @@ public:
};
template<class T>
void printInfo(const UList<T>& list)
{
typedef unsigned long ptrval;
std::cout
<< nl
<< "List : addr: " << ptrval(&list)
<< " (null: " << isNull(list) << ")" << nl
<< " size: " << list.size() << " empty: " << list.empty() << nl
<< " data: " << ptrval(list.cdata())
<< " begin=" << ptrval(list.begin())
<< " end=" << ptrval(list.end()) << nl;
Info<< list << nl;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
int main()
{
// Test pointer and reference to a class
......@@ -23,31 +81,34 @@ int main()
typedef unsigned long ptrval;
Info<<"nullObject address=" << ptrval(&(nullObjectPtr)) << endl;
Info<<"sizeof(nullObject)" << " == "
<< sizeof(NullObject::nullObject)
<< " vs. sizeof(void*)" << " == " << sizeof(void*)
<< endl;
std::cout
<< "nullObject addr=" << ptrval(&(nullObjectPtr)) << nl
<< " sizeof(nullObject) = " << sizeof(NullObject::nullObject) << nl
<< " sizeof(void*) = " << sizeof(void*) << nl
<< " sizeof(labelList) = " << sizeof(labelList) << nl
<< " sizeof(wordHashSet) = " << sizeof(wordHashSet) << nl << nl;
Info<<"nullObject pointer:" << ptrval(nullObjectPtr->pointer()) << endl;
Info<<"nullObject value:" << nullObjectPtr->value() << endl;
std::cout
<< "nullObject" << nl
<< " pointer:" << ptrval(nullObjectPtr->pointer()) << nl
<< " value:" << nullObjectPtr->value() << nl << nl;
if (notNull(ptrToClass))
{
Info<< "Pass: ptrToClass is not null" << endl;
Info<< "Pass: ptrToClass is not null" << nl;
}
else
{
Info<< "FAIL: refToClass is null" << endl;
Info<< "FAIL: refToClass is null" << nl;
}
if (notNull(refToClass))
{
Info<< "Pass: refToClass is not null" << endl;
Info<< "Pass: refToClass is not null" << nl;
}
else
{
Info<< "FAIL: refToClass is null" << endl;
Info<< "FAIL: refToClass is null" << nl;
}
......@@ -58,24 +119,42 @@ int main()
if (isNull(ptrToNull))
{
Info<< "Pass: ptrToNull is null" << endl;
Info<< "Pass: ptrToNull is null" << nl;
}
else
{
Info<< "FAIL: ptrToNull is not null" << endl;
Info<< "FAIL: ptrToNull is not null" << nl;
}
if (isNull(refToNull))
{
Info<< "Pass: refToNull is null" << endl;
Info<< "Pass: refToNull is null" << nl;
}
else
{
Info<< "FAIL: refToNull is not null" << endl;
Info<< "FAIL: refToNull is not null" << nl;
}
// Clean-up
delete ptrToClass;
// Test List casting
{
labelList list1;
labelList list2({1, 2, 3});
printInfo(list1);
printInfo(list2);
printInfo(labelList::null());
printInfo(faceList::null());
printInfo(pointField::null());
}
Info<< nl;
return 0;
}
// ************************************************************************* //
......@@ -2,10 +2,10 @@
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration |
\\ / A nd | Copyright (C) 2017 OpenCFD Ltd.
\\ / A nd | Copyright (C) 2017-2019 OpenCFD Ltd.
\\/ M anipulation |
-------------------------------------------------------------------------------
| Copyright (C) 2014-2016 OpenFOAM Foundation
| Copyright (C) 2014 OpenFOAM Foundation
-------------------------------------------------------------------------------
License
This file is part of OpenFOAM.
......@@ -28,9 +28,11 @@ Class
Description
Singleton null-object class and instance.
Its contents occupy just enough space to also be reinterpreted
Its contents occupy enough space to also be reinterpreted
as another class with a null pointer or zero long for its first
member.
member. There is an additional zero second parameter for safe
casting to List etc.
SourceFiles
nullObjectI.H
......@@ -58,25 +60,35 @@ class NullObject;
class NullObject
{
//- Ensure it occupies enough space to reinterpret_cast to a class
// having some member data
const union
//- A %union of zero data types
union zeros
{
void* ptr;
unsigned long val;
} content;
};
// Private Data
//- The zero data content
zeros data_[4];
// Constructors
//- Private constructor for singleton only
// Could also rely on bit-wise zero initialization for union content
NullObject()
:
data_{nullptr, nullptr, nullptr, nullptr}
{}
//- Private constructor for singleton only
NullObject()
:
content{nullptr}
{}
//- No copy construct
NullObject(const NullObject&) = delete;
//- No copy construct
NullObject(const NullObject&) = delete;
//- No copy assignment
void operator=(const NullObject&) = delete;
//- No copy assignment
void operator=(const NullObject&) = delete;
public:
......@@ -91,13 +103,13 @@ public:
//- A nullptr pointer content
inline const void* pointer() const
{
return content.ptr;
return data_[0].ptr;
}
//- Zero valued integer content
inline unsigned long value() const
{
return content.val;
return data_[0].val;
}
};
......@@ -121,29 +133,29 @@ inline Ostream& operator<<(Ostream& os, const NullObject&)
extern const NullObject* nullObjectPtr;
//- Return reference to the nullObject of type T
//- Reference to the nullObject of type T
template<class T>
inline const T& NullObjectRef();
//- Return pointer to the nullObject of type T
//- Pointer to the nullObject of type T
template<class T>
inline const T* NullObjectPtr();
//- Return true if t is a reference to the nullObject of type T
//- True if t is a reference to the nullObject of type T
template<class T>
inline bool isNull(const T& t);
//- Return true if t is not a reference to the nullObject of type T
//- True if t is not a reference to the nullObject of type T
template<class T>
inline bool notNull(const T& t);
//- Return true if t is a pointer to the nullObject of type T
//- True if t is a pointer to the nullObject of type T
template<class T>
inline bool isNull(const T* t);
//- Return true if t is not a pointer to the nullObject of type T
//- True if t is not a pointer to the nullObject of type T
template<class T>
inline bool notNull(const T* t);
......
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