[boost] boost::variant and "Current Approach: Temporary Heap Backup" vs "An Initial Solution: Double Storage"

Subject: [boost] boost::variant and "Current Approach: Temporary Heap Backup" vs "An Initial Solution: Double Storage"
From: Peter Foelsche (peter_foelsche_at_[hidden])
Date: 2009-09-30 17:18:28

1)
boost::variant and "Current Approach: Temporary Heap Backup" vs "An Initial 
Solution: Double Storage"
Please provide both solutions. A potential heap allocation may prevent 
certain application areas.

2)
I also do not understand that exception safety requires that the variant is 
never empty (e.g. empty() returning always false).
What is the use of calling the constructor (of which type btw?)
if somebody creates an unintialized variant variable?
Or: In the following piece of code is the std::string constructor being 
called?

boost::variant<std::string, int> s;

Thanks
Peter