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Re: [libstdc++] numeric_limits: is_iec559
- From: Richard Henderson <rth at redhat dot com>
- To: Gabriel Dos Reis <gdr at integrable-solutions dot net>
- Cc: Richard Henderson <rth at twiddle dot net>, libstdc++ at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
- Date: Mon, 23 Sep 2002 17:43:02 -0400
- Subject: Re: [libstdc++] numeric_limits: is_iec559
- References: <20020921154554.A2175@twiddle.net> <m3n0qa4hui.fsf@soliton.integrable-solutions.net>
On Sun, Sep 22, 2002 at 09:13:41AM +0200, Gabriel Dos Reis wrote:
> | Indeed, the example numeric_limits<float> in section 18.2.1.5 shows
> | has_denorm=denorm_absent but is_iec559=true. Not that it matters at
> | the moment, since we don't have an target that has this case.
>
> I believe that example is bogus. I'll raise the issue on the Library
> Reflector.
Apparently I spoke too soon. David Edelsohn posted today a synthetic
IBM format that can't represent denormals as LIA-1 defines denormals.
In particular, 2**(emin-p) is not representable.
As currently defined, __LDBL_DENORMAL_MIN__ will evaluate to zero,
so has_denorm will be set to absent, which I think is correct.
So how should we define is_iec559 for this format?
r~