Asko Kauppi <

[hidden email]> writes:

> I've been revising the LNUM patch (more of that later) and spend several

> hours today trying to understand what exactly -ffast-math does with

> regard to NaN's (not-a-numbers).

>

> Basically, it does not seem to know them. It gives nan==nan and other

> no-can-dos that I regard as Completely Evil as to Lua compatibility.

There's a list of what exactly -ffast-math does in the gcc manual (see

Taj Khattra's followup for a quote), but I just wanted to note that you

can tune it by following the -ffast-math option with finer-grained

options that reverse parts of its effect.

E.g., in my proggie, I use:

-ffast-math -fno-finite-math-only -ftrapping-math -fno-associative-math

"-fno-finite-math-only" and "-ftrapping-math" reverse some of the usual

effect of -ffast-math (-fno-associative-math is just to silence a

warning, as -ftrapping-math automatically implies that anyway).

-Miles

--

o The existentialist, not having a pillow, goes everywhere with the book by

Sullivan, _I am going to spit on your graves_.