id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
3658	Remove dependency on static initialization/destruction order	Andrey Semashev	Joaquín M López Muñoz	"The static_holder depends on the static initialization/destruction order, as it is implemented as a function-local static variable. If there are flyweights in the static or global variables, which are initialized lazilly, the flyweight value may get destroyed before the flyweights that refer to it. For example:

{{{
#include <iostream>
#include <string>
#include <boost/shared_ptr.hpp>
#include <boost/flyweight.hpp>
#include <boost/flyweight/key_value.hpp>

struct A
{
	int m_n;

	A(int n) : m_n(n)
	{
		std::cout << ""A()"" << std::endl;
	}
	~A()
	{
		std::cout << ""~A()"" << std::endl;
	}

	bool operator== (A const& a) const
	{
		return m_n == a.m_n;
	}

	friend std::size_t hash_value(A const& a)
	{
		return a.m_n;
	}
};

struct B
{
	boost::flyweight< boost::flyweights::key_value< int, A > > m_A;

	B() : m_A(10)
	{
		std::cout << ""B()"" << std::endl;
	}
	~B()
	{
		std::cout << ""~B()"" << std::endl;
	}
};

boost::shared_ptr< B > p;

int main(int, char*[])
{
	p.reset(new B());
	return 0;
}
}}}

Compiled with MSVC:

{{{
cl -Ox -MD -EHsc -I . -DNDEBUG ./flyweight_test.cpp
}}}

Produces:

{{{
A()
B()
~A()
~B()
}}}

And a crash.

A possible solution would be to destroy flyweight values only when reference counter from flyweights drops to zero.
"	Feature Requests	closed	Boost 1.42.0	flyweight	Boost 1.41.0	Problem	invalid