AddressSanitizer throwing SEGV on unknown address C++ - c++

Question

I have a task where I have to make a class depending on std::multiset. The idea is that it gets 2 multisets in its constructor, they then have to be sorted and put back in those variables while the class is in scope.To provide an example:
std::multiset<int> a;
std::multiset<int> b;
a.insert(4); a.insert(3); a.insert(1); a.insert(10); // a={1,3,4,10}
b.insert(3); b.insert(2); // b={2,3}
if(true){
multisets_merge_view<int>(a,b);
// sorts them and makes it, so that:
// a={1,2,3,3}
// b={4,10}
}
// and here, the multisets need to go back to their original state:
// a={1,3,4,10}
// b={2,3}
We have to work with g++ 9.3.0 under Ubuntu 20.04, with the following flags: -fsanitize=address,leak,undefined -O3 -Wall -Wextra -WerrorThe code - that was given and I cannot touch - to check if everything works correctly:
#include <iostream>
#include <numeric>
#include "msmview.h"
#include <set>
#include <iterator>
#include <string>
#include <algorithm>
#include "msmview.h"
struct string_size_less
{
bool operator()( const std::string& lhs,
const std::string& rhs ) const
{
return lhs.size() < rhs.size();
}
};
const int max = 1000;
bool check()
{
std::multiset<int> a;
std::multiset<int> b;
a.insert( 1 );
a.insert( 7 );
a.insert( 4 );
b.insert( 4 );
b.insert( 3 );
std::multiset<std::string> s;
std::multiset<std::string> t;
s.insert( "C++" );
s.insert( "Pascal" );
s.insert( "Haskell" );
t.insert( "C" );
t.insert( "Ada" );
std::multiset<int> x;
std::multiset<int> y;
for( int i = 0 ; i < max; ++i )
{
x.insert( i );
y.insert( i );
}
bool c = x.count( max / 3 ) == 2;
if ( !c )
{
multisets_merge_view<int> mvi( a, b );
multisets_merge_view<int> mvm( x, y );
multisets_merge_view<std::string> mvs( s, t );
c = x.count( max / 3 ) == 2 && 3 == s.size() &&
0 == s.count( "Pascal" ) && 1 == t.count( "Pascal" ) &&
0 == x.count( max - 1 ) && 1 == s.count( "C" ) &&
0 == a.count( 7 ) && 0 == b.count( 3 );
}
if ( !c || 1 != x.count( max / 3 ) || 1 != s.count( "Pascal" ) ||
0 != s.count( "C" ) || 2 != t.size() || 1 != x.count( max - 1 ) ||
1 != a.count( 7 ) || 1 != b.count( 3 ) )
{
return false;
}
if ( c )
{
const multisets_merge_view<int> mvi( a, b );
const multisets_merge_view<int> mvm( x, y );
const multisets_merge_view<std::string> mvs( s, t );
if ( 5 != mvi.size() || 2 != mvi.count( 4 ) || 0 != mvi.count( max ) ||
5 != mvs.size() || 1 != mvs.count( "C++" ) || 2 * max != mvm.size() ){
return false;
}
}
else
{
std::cout << "neither";
return false;
}
std::multiset<int, std::greater<int> > ga;
std::multiset<int, std::greater<int> > gb;
ga.insert( 0 );
ga.insert( max );
gb.insert( max );
std::multiset<std::string, string_size_less> sa;
std::multiset<std::string, string_size_less> sb;
sa.insert( "C++" );
sa.insert( "Haskell" );
sb.insert( "Ada" );
sb.insert( "SQL" );
sb.insert( "LISP" );
if ( c )
{
const multisets_merge_view<std::string, string_size_less> mvs( sa, sb );
const multisets_merge_view<int, std::greater<int> > mvi( ga, gb );
return 2 == sa.count( "C++" ) && 1 == sb.count( "C++" ) && 1 == gb.count( 0 ) &&
3U == sb.size() && ga.size() == ga.count( max ) && 3 == mvi.size();
}
return false;
}
int main()
{
std::cout
<< "Your solution is "
<< (check() ? "" : "not ")
<< "ready for submission."
<< std::endl;
}
And my code for the upper mentioned class:
#ifndef MSMVIEW_H
#define MSMVIEW_H
#include <set>
template<typename T1, typename T2 = std::greater<T1>>
class multisets_merge_view : public std::multiset<T1,T2>{
public:
multisets_merge_view(std::multiset<T1> &a, std::multiset<T1> &b);
multisets_merge_view(std::multiset<T1,T2> &a, std::multiset<T1,T2> &b);
~multisets_merge_view();
int size() const { return _size; }
int count(T1 t) const;
private:
std::multiset<T1> *_apo;
std::multiset<T1> *_bpo;
std::multiset<T1,T2> *_apt;
std::multiset<T1,T2> *_bpt;
std::multiset<T1> _ao;
std::multiset<T1> _bo;
std::multiset<T1,T2> _at;
std::multiset<T1,T2> _bt;
unsigned int _size;
};
template<typename T1, typename T2>
multisets_merge_view<T1,T2>::multisets_merge_view(std::multiset<T1> &a, std::multiset<T1> &b):_ao(a),_bo(b),_size(a.size()+b.size()){
_apo = &a;
_bpo = &b;
std::multiset<T1> tmp;
tmp.insert(a.begin(),a.end());
tmp.insert(b.begin(),b.end());
a.clear();
b.clear();
for(typename std::multiset<T1>::const_iterator i(tmp.begin()),end(tmp.end()); i!=end; ++i){
if(a.size() < _ao.size()){
a.insert(*i);
}else{
b.insert(*i);
}
}
};
template<typename T1, typename T2>
multisets_merge_view<T1,T2>::multisets_merge_view(std::multiset<T1,T2> &a, std::multiset<T1,T2> &b):_at(a),_bt(b),_size(a.size()+b.size()){
_apt = &a;
_bpt = &b;
std::multiset<T1,T2> tmp;
tmp.insert(a.begin(),a.end());
tmp.insert(b.begin(),b.end());
a.clear();
b.clear();
for(typename std::multiset<T1,T2>::const_iterator i(tmp.begin()),end(tmp.end()); i!=end; ++i){
if(a.size() < _at.size()){
a.insert(*i);
}else{
b.insert(*i);
}
}
};
template<typename T1, typename T2>
multisets_merge_view<T1,T2>::~multisets_merge_view(){
if(_apo != nullptr && _bpo != nullptr){
*_apo = _ao;
*_bpo = _bo;
}else if(_apt != nullptr && _bpt != nullptr){
*_apt = _bt;
*_bpt = _at;
}
};
template<typename T1, typename T2>
int multisets_merge_view<T1,T2>::count(T1 t) const{
int count = 0;
if(_apo != nullptr && _bpo != nullptr){
for(typename std::multiset<T1>::const_iterator i = _ao.begin(); i != _ao.end(); i++){
if(*i==t) count++;
}
for(typename std::multiset<T1>::const_iterator i = _bo.begin(); i != _bo.end(); i++){
if(*i==t) count++;
}
}else if(_apt != nullptr && _bpt != nullptr){
for(typename std::multiset<T1,T2>::const_iterator i = _at.begin(); i != _at.end(); i++){
if(*i==t) count++;
}
for(typename std::multiset<T1,T2>::const_iterator i = _bt.begin(); i != _bt.end(); i++){
if(*i==t) count++;
}
}
return count;
};
#endif
When I run the compiler, AddressSanitizer throws a memory reallocation error found in ~multisets_merge_view(), probably when *_apt=_at; *_bpt=_bt; happens (without providing a second template parameter in the main program, everything works fine, but as I said I can't modify that).
Is there a way to fix this while not touching the main program and still using the -fsanitize=address,leak,undefined?