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Re: [avr-gcc-list] compilation results with avr-gcc 4.8.3

From: Richard Weickelt
Subject: Re: [avr-gcc-list] compilation results with avr-gcc 4.8.3
Date: Fri, 26 Sep 2014 10:44:47 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130330 Thunderbird/17.0.5


>> Is it fair to conclude that the ~
>> operator, applied to an unsigned char, does produce an int as output
>> instead of the input type?
> Yes, this is exactly what the C standard promotion rules require.
> Well, to be exact, they *require* it behaves "as if" it were promoted
> to "int", so if the sign extension has no net effect to the result, it
> might be left out as well.  So in that sense, it might be considered a
> "missed optimization" bug in GCC here, but it's probably always hard
> to catch all those situations well were the integer promotion could be
> bypassed.

I remember vaguely somebody's proposal on this list to write a C++ class for
unsigned char in order to "bypass" promotion rules. Has anyone tried that?
Just being curious.


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