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[Bug libc/17661] some invalid floating point values should be considered as "nan"
- From: "joseph at codesourcery dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Fri, 28 Nov 2014 18:17:47 +0000
- Subject: [Bug libc/17661] some invalid floating point values should be considered as "nan"
- Auto-submitted: auto-generated
- References: <bug-17661-131 at http dot sourceware dot org/bugzilla/>
https://sourceware.org/bugzilla/show_bug.cgi?id=17661
--- Comment #7 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
Most libm functions are not using isnan - they generally examine bits of
the representation directly, often in assembly code (and then e.g. select
what to do based on the value of the exponent, assuming that the high
mantissa bit is valid given those exponent bits).
It seems dubious to complicate lots of separate functions for inputs no
valid program will ever pass in. I'm not sure if the logical handling of
the invalid values (i.e. handling consistent with what hardware operations
do) is consistent between x86/x86_64, ia64, m68k either (certainly there
are some differences between the Intel and m68k versions of the format, at
least, which ldbl-96 code needs to allow for in some cases).
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