Re: [boost] The noexcept Specifier & Block

Subject: Re: [boost] The noexcept Specifier & Block
From: Alexander Terekhov (terekhov_at_[hidden])
Date: 2009-04-18 11:02:20

Peter Dimov wrote:

[... exception specifications and std::unexpected() ...]

> It is not realistic to expect this behavior to be changed, but it might be
> possible to add another handler, separate from std::unexpected, that is
> invoked prior to stack unwinding. 

Since that would effectively mandate two-phase EH, I'd be pretty happy
(with that handler globally set to abort() in all my programs) except
that ...

>                                   But I still do not understand your
> motivation for insisting that this is the correct way to do things. What
> specific practical problems does this solve?

... why-to-abort()-at-unexpected-throw-point aside for a moment,
consider:

  struct X {
    int v;
    X() : v(0) { }
   ~X() { std::cout << v; }
  };

  void f();

  void g() throw() {
    X x;
    f();
    x.v = 42;
  }

with a possibility of stack unwinding due to a throw from f(), compiler
has to either generate redundant initialization store (x.v = 0) or
increase the size of cleanup code to let the X's destructor see 0 in x.v
instead of 42 (on the path of unwinding due to a throw from f()).

I don't want to have either.

regards,
alexander.