Boost logo

Boost :

From: Andreas Pokorny (andreas.pokorny_at_[hidden])
Date: 2005-10-12 10:57:09

We just stumbled across a small problem with Boost.Signals,
while playing with the symbol visibility features of gcc-3.4 and
gcc-4. That feature is still buggy, but it unveiled some strange

Somehow gcc failed to turn the type info of the types stored by any
into a visible symbol, which is required for using boost::signals
across shared libraries. So there are multiple type info objects and
the dynamic_casts within signal failed, and the application crashed
with a seg fault, since no one expected the cast to fail

The code is in signal_template.hpp:

 template<typename Pair>
 R operator()(const Pair& slot) const {
  F* target = const_cast<F*>(any_cast<F>(&slot.second));
  return (*target)(BOOST_SIGNALS_BOUND_ARGS);

I dont see why any_cast is used here at all. The type safety
is guranteed by the interface of Boost.Signals, so I doubt that
someone will be able to abuse the library. I believe the author
of that code had the same in mind, since he did not test
target != 0 before invoking the target. So in my opinion a
simple reinterpret_cast should suffice here. It would also
fix our issue, although that one is caused by gcc.

Andreas Pokorny

Boost list run by bdawes at, gregod at, cpdaniel at, john at