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c.f. bug 424647
List Archive: gentoo-amd64
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To: gentoo-amd64@g.o
From: Frank Peters <frank.peters@...>
Subject: Re: Re: GCC-4.5.2 Has Serious Problems
Date: Thu, 30 Jun 2011 22:43:07 -0400
On Thu, 30 Jun 2011 21:22:39 -0500
Barry Schwartz <chemoelectric@...> wrote:

> 
> C is essentially a glorified assembly language
>

IMO, that's why C is the best.  It is very close to the machine
and the programmer has to be very attentive to details of hardware
as well as to software concepts.

> for bit-twiddling, which the original K&R book encouraged, and which
> this code is doing. So all is well, from my point of view. :)

Bit manipulations on integers and strings are natural.  The difficulty
is with floating point variables which are not just bits but also
a complex format that does not respect byte boundaries.  The ordinary bit
operators cannot apply to floating point.  The only way to ordinarily get
data in/out is to use the built-in conversion routines.  The language was
never designed, AFAIK, to directly manipulate floating point bits.

> Fancy
> optimizations are not to be trusted on assembly code; never be afraid
> to turn them off. You probably don’t need them, anyway. :)
> 

Certainly true.  But in this case, -fno-strict-aliasing is absolutely
necessary.

Also, I, as probably most others, would rather not concentrate so much
on the compiler as on the task of coding itself.

Frank Peters



References:
GCC-4.5.2 Has Serious Problems
-- Frank Peters
Re: GCC-4.5.2 Has Serious Problems
-- Nikos Chantziaras
Re: GCC-4.5.2 Has Serious Problems
-- Nikos Chantziaras
Re: Re: GCC-4.5.2 Has Serious Problems
-- Frank Peters
Re: Re: GCC-4.5.2 Has Serious Problems
-- Barry Schwartz
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Updated Jun 28, 2012

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