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From: "joseph at codesourcery dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/101953] bug on the default cast operator from double to
 unsigned short
Date: Wed, 18 Aug 2021 20:44:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101953

--- Comment #25 from joseph at codesourcery dot com <joseph at codesourcery=
 dot com> ---
The option to use to detect this is -fsanitize=3Dfloat-cast-overflow (note:=
=20
I haven't tested if it detects this particular case).  As per the manual:=20
"Unlike other similar options, @option{-fsanitize=3Dfloat-cast-overflow} is=
=20
not enabled by @option{-fsanitize=3Dundefined}.".  (Annex F makes the resul=
t=20
an unspecified value with "invalid" raised, instead of being undefined=20
behavior, which justifies not including it in -fsanitize=3Dundefined by=20
default.  That means that each time such a conversion occurs in the=20
abstract machine, some value representable in the result type must be=20
produced; it can't be a "wobbly" value where different uses of the result=20
of the conversion, that was only executed once in the abstract machine,=20
act like different values or like values not of the result type.  If such=20
a conversion does produce a wobbly value, that's a bug; see bug 93806=20
comments 27 to 29 for examples of such a bug.)=