Re: Puzzling behaviour of `isnan' with -ffast-math

[Bernd Strieder]

Hello,

Lionel B wrote:

> Is this just because all bets are off with -ffast-math (i.e. undefined
> behaviour) or is there a problem here?

See the docs (info pages):

`-ffinite-math-only'
     Allow optimizations for floating-point arithmetic that assume that
     arguments and results are not NaNs or +-Infs.

`-ffast-math'
     Sets `-fno-math-errno', `-funsafe-math-optimizations',
     `-ffinite-math-only', `-fno-rounding-math', `-fno-signaling-nans'
     and `-fcx-limited-range'.


Bernd Strieder