[Bug c/101953] bug on the default cast operator from double to unsigned short

["joseph at codesourcery dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101953

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