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[Bug libc/13246] RFE: strtold: do not include uninitialized bytes when converting "NaN"
- From: "jakub at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: Thu, 06 Oct 2011 08:15:00 +0000
- Subject: [Bug libc/13246] RFE: strtold: do not include uninitialized bytes when converting "NaN"
- Auto-submitted: auto-generated
- References: <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
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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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