Re: [avr-libc-dev] avr-libc 1.0.5 released

[Paul Schlie]

> From: "E. Weddington" <address@hidden>
>> 
> Which version of the autotools are you trying to use?

autoconf (GNU autoconf) 2.59
automake (GNU automake) 1.8.5

also installing 1.4 etc, isn't an insurmountable problem, just a minor pain,
as there are some cross incompatibles between different autoconf/automake
versions.

>> Also a minor update, I experimented with disabling gcc's default promotion
>> of small integers (char/short) to int; and so far so good, now attempting to
>> also limit promoting enum's and bool's to the smallest integer type with
>> sufficient precision, as opposed to defaulting to int, which 99% of the time
>> will be a char, as most enums tend to be small; but will likely miss some
>> places for similar improvements, as GCC's expression manipulation code is a
>> bit tangled.
>> 
> This would be great

In brief email exchange Richard Henderson, he's already expressed strong
concerns that it may effect proper/compliant C/C++ function selection
semantics, which I've just begun thinking about...

>> But unfortunately don't have a great degree of confidence that it would be
>> easily accepted, as all targets would need to be tested, and although I
>> don't think it would be detrimental to other targets, it may effect some of
>> their optimization assumptions if biased toward assuming int types, but not
>> sure.
> 
> Well, is there any way to make it avr backend specific? That would
> probably make it easier to get it accepted....

Unfortunately I doubt that a target specific patch to the C/C++ front-ends
would be acceptable (that's where the default initial promotions are being
done); and no chance if it does actually affect function selection semantics
(which so far, I'm not convinced it does, although may).

If there's an interest, I can offer a simple patch to c-common.c to
experiment with which basically prevents char/shorts being promoted
initially by default, but doesn't yet affect the promotion of enum/bool
(but as noted earlier, char/short promotion may also occur elsewhere that
I haven't yet identified?)