kicad-developers team mailing list archive

[Wayne Stambaugh <stambaughw@xxxxxxxxx>]

Chris,

I'm fine with committing this as long as it doesn't break anything which
I don't see why it would.

Thanks,

Wayne

On 1/5/2016 11:11 AM, Chris Pavlina wrote:
> Hi,
> 
> layers_id_colors_and_visibility.h defines enum LAYER_ID as unsigned, 
> then #defines two negative constants to be used with the enum. 
> Comparisons of these generate the following warning:
> 
> warning: comparison of constant 4294967295 with expression of type 'int' 
> is always true [-Wtautological-constant-out-of-range-compare]
> 
> 
> Currently there is no problem (I actually dug into the assembler to make 
> sure the comparison was being generated). However, this is a time bomb 
> just waiting for a different compiler version which decides to optimize 
> out what it sees as a tautological comparison, and the fix is very, very 
> simple.
> 
> Attached patch does two things:
> 
> 1) Move the negative constants INTO the enum so that the compiler knows 
> to assign the enum a backing type that supports negatives.
> 
> 2) Remove the unnecessary forced-typing of the enum. There is absolutely 
> no reason this enum has to be an unsigned-char; I suspect this was an 
> instance of overzealous and misguided "optimization". This 
> "optimization" will at best not do anything (as the compiler will decide 
> to pad out the char to the platform's word length anyway), and at worst 
> make things even /slower/ (if the compiler actually decides to access it 
> as a char).
> 
> --
> Chris
> 
> 
> 
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