I have a class that is using boost::aligned storage to statically allocate memory within the object, then initialize the objects at a later time. However, a crash in one test program appears to show the members’ destructors being called on the initialized object, a std::set in this case, when I attempt to return the object after a function call. Then, only the data appears to be copied over on assignment to the new object at the return site, as if the object was a POD type. This means that the next time I attempt to access the assigned object, it fails with a memory access error.
More specifically, I’m implementing a class called StaticVector, a subset of std::vector which attempts to closely match Boost.Array plus size tracking and a compile time fixed capacity.
My test program benchStaticVector runs as follows:
- calls a function that adds a randomly filled std::set to a StaticVector
- returns it to a local variable
- the destructor is being called on the return, but for some reason the returned object isn’t copying correctly
- when the local variable goes out of scope free gets called on uninitialized memory
- Crash
What is the source of this crash, and how do I resolve it?
The full code and a convenient CMakeLists.txt file can be found at:
https://github.com/ahundt/Boost.StaticVector
benchStaticVector.cpp:
// benchmark based on: http://cpp-next.com/archive/2010/10/howards-stl-move-semantics-benchmark/
#include "StaticVector.hpp"
#include <vector>
#include <iostream>
#include <time.h>
#include <set>
#include <algorithm>
#include <exception>
const unsigned N = 3;
extern bool some_test;
template<typename T>
T get_set(std::size_t)
{
T s;
for (std::size_t i = 0; i < N; ++i)
while (!s.insert(std::rand()).second)
;
if (some_test)
return s;
return T();
}
template<typename T>
T generate()
{
T v;
for (std::size_t i = 0; i < N; ++i)
v.push_back(get_set<typename T::value_type>(i));
if (some_test)
return v;
return T();
}
template<typename T>
float time_it()
{
clock_t t1, t2, t3, t4;
clock_t t0 = clock();
{
T v(generate<T>());
}
return (float)((t4-t0)/(double)CLOCKS_PER_SEC);
}
int main()
{
try {
std::cout << "N = " << N << "\n\n";
std::cout << "StaticVector Benchmark:\n";
float t = time_it<boost::StaticVector<std::set<std::size_t>,N > >();
std::cout << "Total time = " << t << "\n\n";
std::cout << "Vector: Benchmark\n";
t = time_it<std::vector<std::set<std::size_t> > >();
std::cout << "Total time = " << t << '\n';
}catch(std::exception e){
std::cout << e.what();
}
}
bool some_test = true;
Here is the class in StaticVector.hpp:
/**
* @file StaticVector.hpp
* @date Feb 23, 2011
* @brief Vector style class with fixed capacity.
*
* The following code declares class StaticVector,
* an STL container (as wrapper) for a statically allocated vector with a constant size limit.
* StaticVector is not accepted as part of boost.
*
* (C) Carnegie Mellon University 2011
* @author Andrew Hundt <ahundt@cmu.edu>
*
* based on boost::array
* The original author site of boost::array is at: http://www.josuttis.com/
* (C) Copyright Nicolai M. Josuttis 2001.
*
* Distributed under the Boost Software License, Version 1.0. (See
* accompanying file LICENSE_1_0.txt or copy at
* http://www.boost.org/LICENSE_1_0.txt)
*
* 09 Oct 2011 - (ath) eliminated construction of objects on initialization of StaticVector
* 23 Feb 2011 - (ath) converted to boost::StaticVector
* 28 Dec 2010 - (mtc) Added cbegin and cend (and crbegin and crend) for C++Ox compatibility.
* 10 Mar 2010 - (mtc) fill method added, matching resolution of the standard library working group.
* See <http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#776> or Trac issue #3168
* Eventually, we should remove "assign" which is now a synonym for "fill" (Marshall Clow)
* 10 Mar 2010 - added workaround for SUNCC and !STLPort [trac #3893] (Marshall Clow)
* 29 Jan 2004 - c_array() added, BOOST_NO_PRIVATE_IN_AGGREGATE removed (Nico Josuttis)
* 23 Aug 2002 - fix for Non-MSVC compilers combined with MSVC libraries.
* 05 Aug 2001 - minor update (Nico Josuttis)
* 20 Jan 2001 - STLport fix (Beman Dawes)
* 29 Sep 2000 - Initial Revision (Nico Josuttis)
*
* Jan 29, 2004
*/
#ifndef BOOST_STATIC_VECTOR_HPP
#define BOOST_STATIC_VECTOR_HPP
#include <boost/config.hpp>
#include <boost/detail/workaround.hpp>
#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
# pragma warning(push)
# pragma warning(disable:4996) // 'std::equal': Function call with parameters that may be unsafe
# pragma warning(disable:4510) // boost::StaticVector<T,N>' : default constructor could not be generated
# pragma warning(disable:4610) // warning C4610: class 'boost::StaticVector<T,N>' can never be instantiated - user defined constructor required
#endif
#include <cstddef>
#include <stdexcept>
#include <boost/assert.hpp>
#if ((BOOST_VERSION / 100) % 1000) > 44
#include <boost/swap.hpp>
#endif
// Handles broken standard libraries better than <iterator>
#include <boost/detail/iterator.hpp>
#include <boost/throw_exception.hpp>
#include <algorithm>
// FIXES for broken compilers
#include <boost/config.hpp>
// Selection of types for internal storage
#include <boost/integer.hpp>
#include <boost/type_traits/alignment_of.hpp>
#include <boost/type_traits/aligned_storage.hpp>
#include <boost/type_traits/has_trivial_destructor.hpp>
namespace boost {
template<class T, std::size_t N>
class StaticVector {
public:
// type definitions
typedef T value_type;
typedef T* pointer;
typedef const T* const_pointer;
typedef T* iterator;
typedef const T* const_iterator;
typedef T& reference;
typedef const T& const_reference;
typedef typename boost::aligned_storage<
sizeof(T),
boost::alignment_of<T>::value
>::type aligned_storage;
typedef typename boost::uint_value_t<N>::least size_type;
typedef std::size_t max_size_type;
typedef std::ptrdiff_t difference_type;
private:
size_type m_size; // fastest type that can accomodate N
aligned_storage elems[N]; // fixed-size array of memory aligned elements of type T
public:
// iterator support
iterator begin() { return reinterpret_cast<iterator>(elems); }
const_iterator begin() const { return reinterpret_cast<const_iterator>(elems); }
const_iterator cbegin() const { return reinterpret_cast<const_iterator>(elems); }
iterator end() { return to_object(m_size); }
const_iterator end() const { return to_object(m_size); }
const_iterator cend() const { return to_object(m_size); }
// reverse iterator support
#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) && !defined(BOOST_MSVC_STD_ITERATOR) && !defined(BOOST_NO_STD_ITERATOR_TRAITS)
typedef std::reverse_iterator<iterator> reverse_iterator;
typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
#elif defined(_MSC_VER) && (_MSC_VER == 1300) && defined(BOOST_DINKUMWARE_STDLIB) && (BOOST_DINKUMWARE_STDLIB == 310)
// workaround for broken reverse_iterator in VC7
typedef std::reverse_iterator<std::_Ptrit<value_type, difference_type, iterator,
reference, iterator, reference> > reverse_iterator;
typedef std::reverse_iterator<std::_Ptrit<value_type, difference_type, const_iterator,
const_reference, iterator, reference> > const_reverse_iterator;
#elif defined(_RWSTD_NO_CLASS_PARTIAL_SPEC)
typedef std::reverse_iterator<iterator, std::random_access_iterator_tag,
value_type, reference, iterator, difference_type> reverse_iterator;
typedef std::reverse_iterator<const_iterator, std::random_access_iterator_tag,
value_type, const_reference, const_iterator, difference_type> const_reverse_iterator;
#else
// workaround for broken reverse_iterator implementations
typedef std::reverse_iterator<iterator,T> reverse_iterator;
typedef std::reverse_iterator<const_iterator,T> const_reverse_iterator;
#endif
reverse_iterator rbegin() { return reverse_iterator(end()); }
const_reverse_iterator rbegin() const {
return const_reverse_iterator(end());
}
const_reverse_iterator crbegin() const {
return const_reverse_iterator(end());
}
reverse_iterator rend() { return reverse_iterator(begin()); }
const_reverse_iterator rend() const {
return const_reverse_iterator(begin());
}
const_reverse_iterator crend() const {
return const_reverse_iterator(begin());
}
StaticVector():m_size(0){}
StaticVector(size_type n, const_reference value):
m_size(n)
{
insert(begin(),n,value);
}
template<typename InputIterator>
StaticVector(InputIterator first, InputIterator last):
m_size(last-first)
{
capacitycheck(size());
std::copy(first,last,begin());
}
template<std::size_t SizeRHS>
StaticVector(const StaticVector<T,SizeRHS>& rhs):
m_size(rhs.size())
{
capacitycheck(rhs.size());
std::copy(rhs.begin(),rhs.end(),begin());
}
~StaticVector(){
destroy_array(::boost::has_trivial_destructor<T>());
m_size=0;
}
void push_back (const_reference x){
capacitycheck(size()+1);
new (to_object(size())) T(x);
m_size++;
}
void pop_back(){
if(!empty()){
to_object(size()-1)->~T();
m_size--;
} else {
boost::throw_exception( std::out_of_range("StaticVector<> pop called on empty container."));
}
}
iterator insert(iterator pos, const_reference x){
capacitycheck(size()+1);
std::copy_backward(pos,end(),end()+1);
*pos = x;
m_size++;
return pos;
}
void insert(iterator pos, max_size_type n, const_reference x){
capacitycheck(size()+n);
std::copy_backward(pos,end(),end()+n);
std::fill(pos,pos+n,x);
m_size+=n;
}
template <typename InputIterator>
void insert(iterator pos, InputIterator first, InputIterator last){
max_size_type n = last - first;
capacitycheck(size()+n);
std::copy_backward(pos,end(),end()+n);
std::copy(first,last,pos);
}
iterator erase(iterator pos){
rangecheck(pos-begin());
pos->~T();
std::copy(pos+1,end(),pos);
m_size--;
return pos;
}
iterator erase(iterator first, iterator last){
std::ptrdiff_t n = last-first;
if (n>0) {
rangecheck(size()-n);
for(iterator it = first; it!=last; it++){
it->~T();
}
std::copy(last,end(),first);
m_size -= n;
}
return first;
}
void clear(){
erase(begin(),end());
}
void resize(max_size_type n, const_reference t = T() ){
capacitycheck(n);
if(n - m_size > 0){
std::fill_n(end(), n-m_size, t);
} else {
erase(begin()+n,end());
}
m_size = n;
}
void reserve(max_size_type n){
capacitycheck(n);
}
// operator[]
reference operator[](max_size_type i)
{
BOOST_ASSERT( i < N || i < size() && "StaticVector<>: out of range" );
return *to_object(i);
}
const_reference operator[](max_size_type i) const
{
BOOST_ASSERT( i < N || i < size() && "StaticVector<>: out of range" );
return *to_object(i);
}
// at() with range check
reference at(max_size_type i) { rangecheck(i); return *to_object(i); }
const_reference at(max_size_type i) const { rangecheck(i); return *to_object(i); }
// front() and back()
reference front()
{
return begin();
}
const_reference front() const
{
return begin();
}
reference back()
{
return *to_object(size()-1);
}
const_reference back() const
{
return *to_object(size()-1);
}
// capacity is constant, size varies
max_size_type size() const { return m_size; }
static max_size_type capacity() { return N; }
bool empty() { return m_size == 0; }
static max_size_type max_size() { return N; }
enum { static_size = N };
// swap (note: linear complexity)
void swap (StaticVector<T,N>& y) {
#if ((BOOST_VERSION / 100) % 1000) > 44
for (size_type i = 0; i < N; ++i)
boost::swap(*to_object(i),*y.to_object(i));
boost::swap(m_size,y.m_size);
#else
std::swap_ranges(begin(),end(),y.begin());
std::swap(m_size,y.m_size);
#endif
}
// direct access to data (read-only)
const_pointer data() const { return elems; }
pointer data() { return elems; }
// use array as C array (direct read/write access to data)
pointer c_array() { return elems; }
// assignment with type conversion
template <typename T2>
StaticVector<T,N>& operator= (const StaticVector<T2,N>& rhs) {
std::copy(rhs.begin(),rhs.end(), begin());
m_size = rhs.size();
return *this;
}
// assign one value to all elements
void assign (const T& value) { fill ( value ); } // A synonym for fill
void fill (const T& value)
{
std::fill_n(begin(),size(),value);
}
// check range (may be private because it is static)
void rangecheck (max_size_type i) const {
if (i >= size()) {
std::out_of_range e("StaticVector<>: index out of range");
boost::throw_exception(e);
}
}
// check range (may be private because it is static)
void capacitycheck (max_size_type i) const {
if (i > capacity()) {
std::out_of_range e("StaticVector<>: index out of capacity");
boost::throw_exception(e);
}
}
private:
inline const_pointer to_object(size_type index) const {
return reinterpret_cast<const_pointer>(elems+index);
}
inline pointer to_object(size_type index) {
return reinterpret_cast<pointer>(elems+index);
}
// T has a trivial destructor, do nothing
inline void destroy_array(const boost::true_type&) {}
// T has a destructor, destroy each object
inline void destroy_array(const boost::false_type&) {
for(iterator first = begin(); first != end(); ++first) {
first->~T();
}
}
}; // class StaticVector
#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
template< class T >
class StaticVector< T, 0 > {
public:
// type definitions
typedef T value_type;
typedef T* iterator;
typedef const T* const_iterator;
typedef T& reference;
typedef const T& const_reference;
typedef typename boost::aligned_storage<
sizeof(T),
boost::alignment_of<T>::value
>::type aligned_storage;
typedef typename boost::uint_value_t<0>::least size_type;
typedef std::size_t max_size_type;
typedef std::ptrdiff_t difference_type;
// iterator support
iterator begin() { return iterator( reinterpret_cast< T * >( this ) ); }
const_iterator begin() const { return const_iterator( reinterpret_cast< const T * >( this ) ); }
const_iterator cbegin() const { return const_iterator( reinterpret_cast< const T * >( this ) ); }
iterator end() { return begin(); }
const_iterator end() const { return begin(); }
const_iterator cend() const { return cbegin(); }
// reverse iterator support
#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) && !defined(BOOST_MSVC_STD_ITERATOR) && !defined(BOOST_NO_STD_ITERATOR_TRAITS)
typedef std::reverse_iterator<iterator> reverse_iterator;
typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
#elif defined(_MSC_VER) && (_MSC_VER == 1300) && defined(BOOST_DINKUMWARE_STDLIB) && (BOOST_DINKUMWARE_STDLIB == 310)
// workaround for broken reverse_iterator in VC7
typedef std::reverse_iterator<std::_Ptrit<value_type, difference_type, iterator,
reference, iterator, reference> > reverse_iterator;
typedef std::reverse_iterator<std::_Ptrit<value_type, difference_type, const_iterator,
const_reference, iterator, reference> > const_reverse_iterator;
#elif defined(_RWSTD_NO_CLASS_PARTIAL_SPEC)
typedef std::reverse_iterator<iterator, std::random_access_iterator_tag,
value_type, reference, iterator, difference_type> reverse_iterator;
typedef std::reverse_iterator<const_iterator, std::random_access_iterator_tag,
value_type, const_reference, const_iterator, difference_type> const_reverse_iterator;
#else
// workaround for broken reverse_iterator implementations
typedef std::reverse_iterator<iterator,T> reverse_iterator;
typedef std::reverse_iterator<const_iterator,T> const_reverse_iterator;
#endif
reverse_iterator rbegin() { return reverse_iterator(end()); }
const_reverse_iterator rbegin() const {
return const_reverse_iterator(end());
}
const_reverse_iterator crbegin() const {
return const_reverse_iterator(end());
}
reverse_iterator rend() { return reverse_iterator(begin()); }
const_reverse_iterator rend() const {
return const_reverse_iterator(begin());
}
const_reverse_iterator crend() const {
return const_reverse_iterator(begin());
}
void push_back (const_reference x){
failed_rangecheck();
}
void pop_back(){
failed_rangecheck();
}
iterator insert(iterator pos, const_reference x){
return failed_rangecheck();
}
void insert(iterator pos, max_size_type n, const_reference x){
failed_rangecheck();
}
template <typename InputIterator>
void insert(iterator pos, InputIterator first, InputIterator last){
failed_rangecheck();
}
iterator erase(iterator pos){
return failed_rangecheck();
}
iterator erase(iterator first, iterator last){
return failed_rangecheck();
}
void clear(){
}
void resize(max_size_type n, const_reference t = T() ){
failed_rangecheck();
}
void reserve(size_type n){
failed_rangecheck();
}
// operator[]
reference operator[](max_size_type /*i*/)
{
return failed_rangecheck();
}
const_reference operator[](max_size_type /*i*/) const
{
return failed_rangecheck();
}
// at() with range check
reference at(max_size_type /*i*/) { return failed_rangecheck(); }
const_reference at(max_size_type /*i*/) const { return failed_rangecheck(); }
// front() and back()
reference front()
{
return failed_rangecheck();
}
const_reference front() const
{
return failed_rangecheck();
}
reference back()
{
return failed_rangecheck();
}
const_reference back() const
{
return failed_rangecheck();
}
// size is constant
static max_size_type size() { return 0; }
static bool empty() { return true; }
static max_size_type max_size() { return 0; }
enum { static_size = 0 };
void swap (StaticVector<T,0>& /*y*/) {
}
// direct access to data (read-only)
const T* data() const { return 0; }
T* data() { return 0; }
// use array as C array (direct read/write access to data)
T* c_array() { return 0; }
// assignment with type conversion
template <typename T2>
StaticVector<T,0>& operator= (const StaticVector<T2,0>& ) {
return *this;
}
// assign one value to all elements
void assign (const T& value) { fill ( value ); }
void fill (const T& ) {}
// check range (may be private because it is static)
static reference failed_rangecheck () {
std::out_of_range e("attempt to access element of an empty StaticVector");
boost::throw_exception(e);
#if defined(BOOST_NO_EXCEPTIONS) || !defined(BOOST_MSVC)
//
// We need to return something here to keep
// some compilers happy: however we will never
// actually get here....
//
static T placeholder;
return placeholder;
#endif
}
};
#endif
// comparisons
template<class T, std::size_t N>
bool operator== (const StaticVector<T,N>& x, const StaticVector<T,N>& y) {
return std::equal(x.begin(), x.end(), y.begin());
}
template<class T, std::size_t N>
bool operator< (const StaticVector<T,N>& x, const StaticVector<T,N>& y) {
return std::lexicographical_compare(x.begin(),x.end(),y.begin(),y.end());
}
template<class T, std::size_t N>
bool operator!= (const StaticVector<T,N>& x, const StaticVector<T,N>& y) {
return !(x==y);
}
template<class T, std::size_t N>
bool operator> (const StaticVector<T,N>& x, const StaticVector<T,N>& y) {
return y<x;
}
template<class T, std::size_t N>
bool operator<= (const StaticVector<T,N>& x, const StaticVector<T,N>& y) {
return !(y<x);
}
template<class T, std::size_t N>
bool operator>= (const StaticVector<T,N>& x, const StaticVector<T,N>& y) {
return !(x<y);
}
// global swap()
template<class T, std::size_t N>
inline void swap (StaticVector<T,N>& x, StaticVector<T,N>& y) {
x.swap(y);
}
#if defined(__SUNPRO_CC)
// Trac ticket #4757; the Sun Solaris compiler can't handle
// syntax like 'T(&get_c_array(boost::StaticVector<T,N>& arg))[N]'
//
// We can't just use this for all compilers, because the
// borland compilers can't handle this form.
namespace detail {
template <typename T, std::size_t N> struct c_array
{
typedef T type[N];
};
}
// Specific for boost::StaticVector: simply returns its elems data member.
template <typename T, std::size_t N>
typename detail::c_array<T,N>::type& get_c_array(boost::StaticVector<T,N>& arg)
{
return arg.elems;
}
// Specific for boost::StaticVector: simply returns its elems data member.
template <typename T, std::size_t N>
typename const detail::c_array<T,N>::type& get_c_array(const boost::StaticVector<T,N>& arg)
{
return arg.elems;
}
#else
// Specific for boost::StaticVector: simply returns its elems data member.
template <typename T, std::size_t N>
T(&get_c_array(boost::StaticVector<T,N>& arg))[N]
{
return arg.elems;
}
// Const version.
template <typename T, std::size_t N>
const T(&get_c_array(const boost::StaticVector<T,N>& arg))[N]
{
return arg.elems;
}
#endif
#if 0
// Overload for std::array, assuming that std::array will have
// explicit conversion functions as discussed at the WG21 meeting
// in Summit, March 2009.
template <typename T, std::size_t N>
T(&get_c_array(std::array<T,N>& arg))[N]
{
return static_cast<T(&)[N]>(arg);
}
// Const version.
template <typename T, std::size_t N>
const T(&get_c_array(const std::array<T,N>& arg))[N]
{
return static_cast<T(&)[N]>(arg);
}
#endif
} /* namespace boost */
#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
# pragma warning(pop)
#endif
#endif /*BOOST_STATIC_VECTOR_HPP*/
You broke the rule of three. You need a copy constructor. Note that your constructor taking
const StaticVector<T,SizeRHS>&is not a copy constructor as it is a template. Hence when aStaticVectoris copied (e.g. possibly when returned from a function) the compiler generated copy constructor is used, copying the storage (that’s okay, it’s a POD). At destruction time, the destructor accesses the storage as if it contained live objects, and that’s terrible.