ieeeFlags do not work properly

[Don]

Torben Hagerup wrote:
> Run under D version 2.037, the program below runs through without raising any assert exceptions. This shows an erratic behavior with respect to ieeeFlags that is hardly intended. Other ieeeFlags also work (or, rather, do not work) in unexpected ways.
> 
> --------------------

This isn't a bug.

> import std.math;
> 
> void main() {
> // The execution leads to no assert errors
>  real a,b=3.5;
>  resetIeeeFlags();
>  assert(!ieeeFlags.divByZero); // so far no zero division
>  a=3.5/0.0L; // but now ...

This occurred at compile time. At runtime, this became:
a = real.infinity;

>  assert(a==real.infinity); // yes, exactly
>  assert(!ieeeFlags.divByZero); // perhaps not, after all
>  b/=0.0L; // once more, the same, really

It's not the same. This is a runtime division by zero.

>  assert(b==real.infinity); // yes, the same
>  assert(ieeeFlags.divByZero); // oops, not the same after all?
> }