On 06/02/2017 02:12 PM, Steven Schveighoffer wrote:
Perhaps an intermediate solution would be to offer a compiler switch
that allows Errors to be safely caught (that is, they behave as
exceptions). As far as I understand from reading this thread, that's
already the case in debug builds, so it cannot be that bad practice, but
it would be nice to have a mode that it's otherwise "release", only with
this feature turned on.
I don't think this is workable, simply because of nothrow. An Error is
allowed to be thrown in nothrow code, and the compiler can
simultaneously assume that nothrow functions won't throw. Therefore it
can legally omit the scaffolding for deallocating scope variables when
an Exception is thrown (for performance reasons), and leave your program
in an invalid state.
Well, as I understood from this thread this is already possible in debug
mode:
An Exception leads to unwinding&cleanup, an Error to termination (with
unwinding&cleanup in debug mode for debugging purposes).
If it is indeed so, then adding a switch that only removes this
optimization (from @nothrow code) but is otherwise a release version
shouldn't be too hard to implement? Even if not, making @nothrow a no-op
w.r.t. unwinding should still be possible and not too hard (sorry if I'm
being naïve here, I don't know how hard it would be to implement, but
conceptually it seems straightforward).
Of course, one must be willing to take the performance hit.
