Re: [boost] Build breaking changes

Subject: Re: [boost] Build breaking changes
From: James E. King, III (jking_at_[hidden])
Date: 2018-03-29 13:05:52

On Wed, Mar 28, 2018, 10:51 PM Vinnie Falco via Boost <boost_at_[hidden]>
wrote:

> On Wed, Mar 28, 2018 at 5:49 PM, Andrey Semashev via Boost
> <boost_at_[hidden]> wrote:
> > If someone wants to target an outdated architecture (and 32-bit x86
> really is
> > a separate architecture, including hardware features and software ABI)
> then
> > let them do that with a little more effort. The rest of the world have
> moved to 64 bits
> > long ago, and that is what we should target by default, IMO.
>
> No they have not all "moved on to 64 bits." Most programs work
> perfectly fine as 32-bit applications and have no need for the ability
> to access a full 64-bit address space. In fact many programs perform
> objectively worse as 64-bit application since pointers and data
> structures become larger without a corresponding benefit. This is
> especially true for mobile applications.
>
> Rumors of 32-bit apps' demise are greatly exaggerated.
>

The corresponding benefit is access to twice as many CPU registers (on
amd64, anyway) which provides a notable performance benefit to many
applications (given a compiler outputting code that leverages it).  I don't
know if the same can be said for other 64-bit architectures.  amd64 was
released in 2000.  The debian project reported that in 2012, downloads of
the x86_64 architecture surpassed the x86 architecture.  The addition of
the NX bit is a security improvement in amd64 that x86 cannot leverage, and
given what we've seen recently, CPU enforced security (and correctness) is
pretty important.  We're not saying that we won't support 32-bit, however
if someone just says "b2" on an x86 based platform it should default to an
address-model of 64 unless otherwise overridden.

- Jim

>