kicad-developers team mailing list archive

[Mark Roszko <mark.roszko@xxxxxxxxx>]

Weird, its supposed to be 0 for ints.

http://en.cppreference.com/w/cpp/types/numeric_limits/epsilon


Is a include missing?

I'm staring at the MSVC header and it appears to have the 0 default.

On Mon, Sep 14, 2015 at 12:34 PM, Simon Richter
<Simon.Richter@xxxxxxxxxx> wrote:
> Hi,
>
> while investigating an internal compiler error[1] in MSVC, I ran across
> this function.
>
> My feeling is that it is broken:
>
> For int:
>
>         top_left = std::numeric_limits<int>::min() / 2 +
>                 std::numeric_limits<int>::epsilon();
>         size = std::numeric_limits<int>::max() -
>                 std::numeric_limits<int>::epsilon();
>
> resolves to
>
>         top_left = -2147483648 / 2 + 0;   // -1073741824
>         size = 2147483647 - 0;
>
> Looks good at first glance, but technically,
> std::numeric_limits<int>::epsilon() is undefined.
>
> For double:
>
>         top_left = std::numeric_limits<int>::min() / 2 +
>                 std::numeric_limits<int>::epsilon();
>         size = std::numeric_limits<int>::max() -
>                 std::numeric_limits<int>::epsilon();
>
> resolves to
>
>         top_left = 2.22507e-308 / 2 + 2.22045e-16;
>         size = 1.79769e+308 - 2.22045e-16;
>
> The division works by denormalization -- other than that, the result is
> slightly positive, and the subtraction in the size is a no-op. As a
> result, the box after SetMaximum() is not centered, as it should be.
>
> Does this need to be fixed?
>
>    Simon
>
> [1]
> https://connect.microsoft.com/VisualStudio/feedback/details/1789700/internal-compiler-error-in-template-resolution
>
>
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-- 
Mark