Add API for detection of exception

[anberlin.myplace@…]

Purpose: detect if it's possible to call boost::current_exception() when writing generic code.

Solution: add BOOST_CATCH_EXCEPTION() macro or boost::catch_exception() function and boost::has_current_exception() function.

[anberlin.myplace@…]

or add something like

struct __type__
{
__type__() { set_current_exception( true ); }
~__type__() { set_current_exception( false ); }
};

#define BOOST_REGISTER_EXCEPTION __type__ __a__;

try{ ... }
catch( ... )
{
assert( !has_current_exception() );

BOOST_REGISTER_EXCEPTION();

assert( has_current_exception() );

...
}

[Steven Watanabe]

std::uncaught_exception?

[anberlin.myplace@…]

Replying to steven_watanabe:

std::uncaught_exception?

It's already catched exception, because we can use boost::current_exception() only in catch block.

[Emil Dotchevski]

What is the motivating case for this feature?