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Subject: Re: [boost] [#pragma once]
From: Matt Calabrese (rivorus_at_[hidden])
Date: 2012-11-16 19:33:40

I'm basically with everyone who's been saying to just not bother using
"#pragma once" since the idiomatic ifdef guards work fine and unless there
are some real benchmarks, I don't think it's worthwhile trying to bend over
backwards to take advantage of something that's non-standard. I'm just not
convinced there are any actual gains here.

On Fri, Apr 10, 2009 at 11:33 AM, Remko Tronçon <remko_at_[hidden]> wrote:

> Anyway, I understand that a library like Boost doesn't want to rely on
> this, but personally, but it sounds sane to me that other projects
> (that are less depended on and don't need to support a gazillion of
> compilers) use it.

Alright, I'll agree with this. While I'm not convinced it's a great idea
for boost to use #pragma once, a library macro for users that uses it when
available might make sense. Assuming _Pragma support, it's trivial to
provide a macro BOOST_INCLUDE_ONCE that is defined as _Pragma( "once" ) in
compilers that support it and nothing in compilers that don't (avoiding
possible unrecognized pragma warnings). An alternative is a macro that
produces a compile-time error if it's not supported.

-Matt Calabrese

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