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From: "jakub at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sources.redhat.com
Subject: [Bug libc/13246] RFE: strtold: do not include uninitialized bytes when converting "NaN"
Date: Thu, 06 Oct 2011 08:16:00 -0000	[thread overview]
Message-ID: <bug-13246-131-aP602lhGKa@http.sourceware.org/bugzilla/> (raw)
In-Reply-To: <bug-13246-131@http.sourceware.org/bugzilla/>

http://sourceware.org/bugzilla/show_bug.cgi?id=13246

Jakub Jelinek <jakub at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at redhat dot com

--- Comment #4 from Jakub Jelinek <jakub at redhat dot com> 2011-10-06 08:15:00 UTC ---
I think it is neither.  On x86_64/i686, the hw long double is 80 bit, but
sizeof (long double) is 16 (on x86_64) resp. 12 (on i686).  If you store a long
double from a hw register into memory, it only stores there the 80 bits, the
remaining bits are left unmodified, it is padding that is ignored, thus e.g. if
it is stored
onto the stack, whatever bits were in the padding before are kept there.
It is a bug to look for something meaningful among the padding bits.
That is similar to looking at padding in structures, undefined behavior in C.

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  parent reply	other threads:[~2011-10-06  8:16 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-10-01 17:39 [Bug libc/13246] New: " jim at meyering dot net
2011-10-05 14:52 ` [Bug libc/13246] " schwab@linux-m68k.org
2011-10-05 22:10 ` bugdal at aerifal dot cx
2011-10-06  7:57 ` schwab@linux-m68k.org
2011-10-06  8:16 ` jakub at redhat dot com [this message]
2011-10-06  8:33 ` jim at meyering dot net
2011-10-06  8:46 ` jakub at redhat dot com
2011-10-06  9:31 ` jim at meyering dot net
2011-10-06  9:41 ` schwab@linux-m68k.org
2011-10-06  9:48 ` jim at meyering dot net
2011-10-06  9:57 ` jakub at redhat dot com
2011-10-06 12:40 ` bugdal at aerifal dot cx
2014-06-27 11:59 ` fweimer at redhat dot com

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