google3/third_party/grte/v4_src/glibc-2.19/bits/nan.h - GRTEv4 - Git at Google

 #ifndef _MATH_H
 #error "Never use <bits/nan.h> directly; include <math.h> instead."
 #endif

 /* This file should define `NAN' on machines that have such things.  */
	#ifndef _MATH_H
	#error "Never use <bits/nan.h> directly; include <math.h> instead."
	#endif

	/* This file should define `NAN' on machines that have such things. */