https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112449

--- Comment #9 from joseph at codesourcery dot com <joseph at codesourcery dot 
com> ---
To quote the C23 DIS, "This annex does not require the full support for 
signaling NaNs specified in IEC 60559. This annex uses the term NaN, 
unless explicitly qualified, to denote quiet NaNs.".

Support for signaling NaNs is indicated by FE_SNANS_ALWAYS_SIGNAL in 
<fenv.h>, which glibc makes sure to define only if __SUPPORT_SNAN__ (which 
is defined by GCC if -fsignaling-nans).

If -fsignaling-nans is not used, you should not expect consistency in 
whether a signaling NaN is handled differently from a quiet NaN (including 
whether optimizations might be applied that result in a signaling NaN 
result from an operation that can't produce such a result with IEEE 
signaling NaN semantics).

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