Re: How on earth did noexcept get through the standards process?
Martin B. wrote:
On 04.04.2011 21:04, dietmar_kuehl@yahoo.com wrote:
On Apr 4, 12:20 am, "Martin B."<0xCDCDC...@gmx.at> wrote:
How will the GCC developers produce better code via noexcept? How
will
the compiler team at Intel turn `noexcept` into a performance
advantage? Will Microsoft ignore it like it did with `throw()` ?
Does anyone know of an article or explanation from compiler
implementers
that describes how compilers will be able to use the `noexcept`
sematics to good effect to produce better code?
Given that the feature was introduced only fairly recently and in
a rush as well, I doubt that there will be much written up on it.
However, I would assume that the main target of the optimizations
is actually the library rather than the compiler. I haven't look
at updating my container implementation, yet, but I can image a
number of places where I could use more efficient approaches if I
don't need to be prepared for recovering after an exception.
Do I understand this correctly: The intent would be for the (std)
library implementation to contain (specialized) code to work with
(e.g. move ops) marked as `noexcept` and this code could then be
written differently/more-efficiently from the library code that
worked with ops not marked such?
The <utility> section, in addtion to std::move and std::forward, has a
move_if_noexcept() function that helps containers choose between
moving and copying elements. The idea is to move if that is safe, and
fall back to copying if move might throw.
The problem is of course that a container, like std::vector, that has
to reallocate can't survive a throwing move halfway through the
reallocation without losing half its contents.
Bo Persson
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