The default behavior in every OS with which I'm familiar (this is specified by IEEE-754) is for x87, SSE, VFP and NEON not to trap on signaling NaNs. You have to explicitly unmask the invalid floating-point exception in order for this to trap. All that would happen with the default floating-point environment is that the invalid flag would be raised in FPCR.
IIRC, FSTP st(0), to simply clear the stack without using the result as discussed in the article, doesn't even generate #IA, so it can't trap or raise invalid (it only generates #IA when the store converts to a smaller FP type (fun fact: this is so FLD/FSTP could be used to implement memcpy way back when))
IIRC, FSTP st(0), to simply clear the stack without using the result as discussed in the article, doesn't even generate #IA, so it can't trap or raise invalid (it only generates #IA when the store converts to a smaller FP type (fun fact: this is so FLD/FSTP could be used to implement memcpy way back when))