Re: [boost] Proposal for #pragma once support

Subject: Re: [boost] Proposal for #pragma once support
From: Zachary Turner (divisortheory_at_[hidden])
Date: 2009-06-11 14:42:33

On Thu, Jun 11, 2009 at 1:34 PM, Emil Dotchevski
<emildotchevski_at_[hidden]>wrote:

> On Thu, Jun 11, 2009 at 11:15 AM, Zachary Turner<divisortheory_at_[hidden]>
> wrote:
>
> > Even if we do remove a bunch of stuff from headers, it can still be made
> > faster.  Now matter how many ways you approach the problem, choosing to
> > ignore one specific way that actually makes a serious difference simply
> > because it only works on a subset of compilers is fundamentally
> inconsistent
> > with the notion of developing a cross platform C++ library that works on
> > every compiler.
>
> In a company I worked at, it took ~40 minutes to do a full rebuild of
> the project I worked on. Their solution was to install IncrediBuild,
> and overnight build times went down to ~7 minutes total. That's fast
> right? Worth doing? More than #pragma once? Except that two years
> later the build times were up to over 30 minutes again _with_
> IncrediBuild. :)
>

I guess I just don't see where the "more than" comes from.  If something is
worth doing it's worth doing, independent of what else may or may not be
worth doing.  Whether something gives a "bigger" performance improvement is
beside the point.  For one thing, removing lots of stuff from existing
headers as you suggest is a much larger undertaking than simply adding a few
lines of code at the top of (almost) every header file.  Does the
cost/benefit ratio make it worth doing?   More than #pragma once?   ;-)