https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88683
--- Comment #2 from Martin Jansche <mjansche at google dot com> --- Yeah, looks definitely related. Details may depend on the ultimate diagnosis. Similar observation here that it matters whether NaN appears on the left-hand side vs. right-hand side of a comparison (cf. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88173#c5). Additional notes: * When/whether this surfaces depends to some extent on the version of gcc. I first thought it was a simple regression between gcc-7 and gcc-8, but it's more complex than that. * The title of Bug 88173 could be interpreted to leave open the possibility that this might be a library issue, i.e. std::numeric_limits<>::quiet_NaN() not being declared constexpr. But it's definitely not a library issue. Anyway, I agree with the recommended disposition as DUP. But I'm new around here and don't know who gets to close this as DUP. Happy to do it myself, just don't want to jump the gun.
