Is it safe to pass boost::variant to (from) dll?

Question

Consider this code

typedef boost::variant<int, std::string> var_t;

// this interface class will be implemented in DLL
class producer
{
public:
  virtual var_t produce() = 0;
};

// this class will be implemented by DLL user and 
// pointer to object of this class will be passed to producer
// as callback interface
class produce_handler
{
public:
  virtual void handle_produce(const var_t&) = 0;
};

It is known that it is generally unsafe to pass STD objects through dynamic library boundary. What about boost types, especially variant?

same problems with boost as with std. always depend on compiler/compiler-version/boost version. — user1810087, Mar 27 '14 at 12:47
Also, there is a `std::string` in that `variant`: how magic do you think `variant` is? — Yakk - Adam Nevraumont, Mar 27 '14 at 13:08

score 1 · Accepted Answer · answered Mar 27 '14 at 13:05

If you can guarantee that all modules involved share the same toolchain/options (i.e. ABI), there should be no real trouble^[1].

Regardless of this:

Also, if you know that the "other" module is never going to do anything other than store and pass a reference back to the caller, then there shouldn't be a problem either.

As soon as you start passing these things by value and/or indirecting the references/pointers in a "foreign" module I'd say you need to be very sure your platform supports this and test it.

^[1] outside separate issues, such as the ability to throw/catch exceptions across shared library boundaries; this is related bot not confined to any (or RTTI in general)

Is it safe to pass boost::variant to (from) dll?

1 Answers1