Boost logo

Boost :

Subject: Re: [boost] Formal Review: Boost.Polygon starts today August 24, 2009
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2009-08-31 13:07:38

Joachim Faulhaber wrote:
> with msvc-9 I get a lot of warnings from expressions like
> bool bit2 = atr_ & 4;
> or
> bool bit2 = (bool)(atr_ & 4);
> e.g.
> boost\polygon\transform.hpp(256) : warning C4800: 'int' :
> forcing value to bool 'true' or 'false' (performance warning)
> A big amount of these can be silenced by the simple replacement
> bool bit2 = (atr_ & 4) != 0;

That's a ridiculous warning that we always disable. I've never compared the assembly produced by various compilers, but I'd be wary of the effect on optimization between the two without proof that there is none.

BTW, Lucanus, the C-style cast could be eliminated if you used direct-initialization:

   bool bit2(atr_ & 4);

Rob Stewart robert.stewart_at_[hidden]
Software Engineer, Core Software using std::disclaimer;
Susquehanna International Group, LLP

IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.

Boost list run by bdawes at, gregod at, cpdaniel at, john at