Linux-kernel mailing list archive 1998-31,: Re: floating-point abuse in 2.1.113

# Re: floating-point abuse in 2.1.113

Steve VanDevender (stevev@efn.org)
Thu, 6 Aug 1998 17:04:35 -0700 (PDT)

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Andi Kleen writes:
> Mikael Pettersson <mikpe@csd.uu.se> writes:
>
> > 4. The C language doesn't guarantee this behaviour. While empirical
> > evidence suggests that gcc will evaluate FP constant expressions
> > at compile-time, this is really dodgey and beyond specs.
> > By Murphy's law, this _will_ break at some point.
>
> But Linux kernel not allowing FP is also beyond specs (the C standard
> requires floating point - it is not a optional feature). The spec for
> the C language used in the Linux kernel is the language understood by
> gcc, and it is quite clear that gcc knows how to do it.

Oh puh-leeze. The Linux kernel doesn't use floating-point
because hardware floating point isn't available on some
architectures (i.e. i386 without an i387) and the 387 emulation
isn't meant to handle FPU traps from kernel space. In any case
claiming that the kernel should be able to use absolutely any
standard C language feature is silly -- it's an operating system
kernel, and has to work under more stringent conditions than
apply to user C programs.

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