Memory tracker with overloaded new/delete.

memtracker.cpp

#include <iostream>
#include <memory>
#include <cstdlib>
#include <unordered_map>
#include <stdexcept>
using namespace std;

template <int MAX_TABLE_SIZE=1024>
class MemTracker {
	pair<void*, bool> mem_tbl[MAX_TABLE_SIZE];
	int mem_counter;
	static MemTracker* instance;

	void init_table() {
		for(int i=0;i<MAX_TABLE_SIZE;++i) mem_tbl[i] = make_pair(nullptr, false);
	}
	
	int hash(void* ptr) {
		int pos = reinterpret_cast<uint64_t>(ptr) % MAX_TABLE_SIZE;
		cout << "hash loc = " << pos << endl;
		return pos;
	}

public:	
	MemTracker() : mem_counter(0) {
		init_table();
	}

	bool set(void* ptr) {
		int pos = hash(ptr);
		
		int pos0 = pos;
		bool good = true;
		while(mem_tbl[pos].second) {
			++pos;
			pos %= MAX_TABLE_SIZE;
			cout << "probing position " << pos << endl;
			if(pos == pos0) {
				good = false;
				break;
			}
		}
		if(!good) return false;
		cout << "storing pointer " << ptr << " at " << pos << endl;
		mem_tbl[pos] = make_pair(ptr, true);
		++mem_counter;
		return true;
	}
	
	bool reset(void* ptr) {
		if(ptr == nullptr) return true;
		
		int pos = hash(ptr);
		
		int pos0 = pos;
		bool good = true;
		while(mem_tbl[pos].first != ptr) {
			++pos;
			pos %= MAX_TABLE_SIZE;
			cout << "probing position " << pos << endl;
			if(pos == pos0) {
				good = false;
				break;
			}
		}
		if(!good) return false;
		cout << "removing pointer " << ptr << " at " << pos << endl;
		mem_tbl[pos] = make_pair(nullptr, false);
		--mem_counter;
		return true;
	}
	
	int count() const {
		return mem_counter;
	}
};

MemTracker<15> pool;

void* operator new(size_t sz) throw() {
	try {
		auto ptr = malloc(sz);
		cout << "allocating " << sz << " bytes at " << ptr << endl;
		if(pool.set(ptr)) return ptr;
		else {
			free(ptr);
			throw bad_alloc();
		}
	}
	catch(exception& e) {
		cout << "Critical error: " << e.what() << endl;
		exit(1);
	}
}

void operator delete(void* ptr) {
	try{
		cout << "deallocating at " << ptr << endl;
		if(pool.reset(ptr)) free(ptr);		
		else throw runtime_error("deleting an uninitialized pointer.");
	}
	catch(exception& e) {
		cout << "Critical error: " << e.what() << endl;
	}

}

int main(int argc, char** argv) {
    std::cout << "Hello World!\n";

	int n = 15;
	int* a[n];
	for(int i=0;i<n;++i) {
		a[i] = new int;
		cout << pool.count() << " allocated." << endl;
	}

	for(int i=0;i<n;++i) delete a[i];
	
	return 0;
}