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[Bug-gforth] [bug #50221] FP operations produce unexpected NaNs

From: Anton Ertl
Subject: [Bug-gforth] [bug #50221] FP operations produce unexpected NaNs
Date: Sat, 4 Feb 2017 15:52:20 +0000 (UTC)
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Firefox/38.0 Iceweasel/38.5.0

Update of bug #50221 (project gforth):

                  Status:               Need Info => Confirmed              


Follow-up Comment #3:

Yes, it's definitely not a NaN coming out of the computation:

1 53 lshift 1- s>f 1 53 lshift s>f f/ fdup f= .

prints -1 (for a Nan we would see 0).

And it is really the FP->String conversion (REPRESENT on the
Forth level, ecvt_r on the C level).  It works with the ecvt_r
from glibc 2.19 on AMD64.  Unfortunately it does not work
reliably with our own ecvt_r replacement, either:

2e0 -53e0 f** fconstant eps
1e0 eps f- pad 20 represent .s cr pad 20 dump

This produces an "invalid" result (and the ":" in the string).

So I consider this to be a bug in MacOS X's ecvt_r and in our own
ecvt_r replacement; and ideally we should be checking for this bug in
our configure script so that our then-fixed ecvt_r replacement is used
instead of the broken MacOS X ecvt_r.

Thank you for the bug report.


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