Date: Mon, 31 Mar 2003 23:18:10 +0200
From: "Eli Zaretskii" <eliz AT elta DOT co DOT il>
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To: rich AT phekda DOT freeserve DOT co DOT uk
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In-reply-to: <3E888DDF.21E2114F@phekda.freeserve.co.uk> (message from Richard
	Dawe on Mon, 31 Mar 2003 19:50:07 +0100)
Subject: Re: _doprnt and NaNs
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> Date: Mon, 31 Mar 2003 19:50:07 +0100
> From: Richard Dawe <rich AT phekda DOT freeserve DOT co DOT uk>
> 
> The code in _doprnt (well, cvtl and isspeciall) works with floats stored in
> long doubles. When you do, say:
> 
>     printf("%f", NAN);
> 
> the NAN is first converted in _doprnt to a double by the va_arg macro, then to
> a long double.
> 
> So NAN does not appear as "nan" or "nan(0x7fffff)", as you might expect. It
> appears as "nan(0xffffff00000000)". 

If indeed there's no format specifier for a float (I don't have time
to dig into C9x, but I thought there was something like %hf, no?),
then it would at least be nice to be able to distinguish between a
double and a long double NaN.

So how about some code that would detect NaNs early on, before they
are converted to a long double?