Re: [boost] [exception][policy]

From: Emil Dotchevski (emil_at_[hidden])
Date: 2008-08-29 14:57:44

On Thu, Aug 28, 2008 at 9:21 PM, vicente.botet <vicente.botet_at_[hidden]> wrote:
> The main problem comes from the fact exception_ptr current_exception() do
> not works for any exception. So Emil has found that boost::throw could be
> used to throw a boost::exception wrapping the intendeed exception. IMHO, the
> exception_ptr emulation (without language support) to transport exceptions
> between threads is not of real use if current_exception()  do not works for
> any exception.

As per http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2179.html
current_exception works for any exception. This is what we should aim
for.

Antony has already provided a MSVC-specific implementation that works
for any exception. As soon as I find the time to integrate this into
Boost Exception, boost::enable_current_exception will be a noop on
MSVC.

In principle, every compiler has the machinery necessary to implement
current_exception completely non-intrusively. I am not a compiler
expert, but it seems likely that compiler-specific solution should be
possible for GCC as well.

In my opinion boost::exception_ptr provides very useful functionality.
It is enabled by boost::enable_current_exception, which
boost::throw_exception allows us to inject non-intrusively. If the
cost of boost::enable_current_exception is a problem, this can be
viewed as a motivating force to provide compiler-specific
non-intrusive support for boost::exception_ptr (however I request that
we don't discuss the cost of boost::enable_current exception until I
get a chance to fully test the refactoring pass I've done on the
exception library.)

Emil Dotchevski
Reverge Studios, Inc.
http://www.revergestudios.com/reblog/index.php?n=ReCode