/usr/include/ivstd/nan.h is in ivtools-dev 1.2.11a1-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | #ifndef ivtools_nan_h
#define ivtools_nan_h
#if defined(__GLIBC__) && (__GLIBC__==2 && __GLIBC_MINOR__>0 || __GLIBC__>2)
#include <bits/nan.h>
#elif !defined(__CYGWIN__) && !defined(__NetBSD__) && !defined(__FreeBSD__) && !defined(__APPLE__)
#include_next <nan.h>
#else
#include <math.h>
#endif
#if defined(__sun__) && defined(__svr4__)
#include <ieeefp.h>
#endif
#if defined(__sun__) && defined(__svr4__) || defined(__CYGWIN__) || defined(__linux__) || defined(__NetBSD__) || defined(__FreeBSD__) || defined(__APPLE__)
#define isnanorinf(dval) (!finite(dval))
#elif defined(__alpha)
#define isnanorinf(dval) (IsNANorINF(dval))
#else
#define isnanorinf(dval) (!finite(dval)) /* (dval==NAN || dval==INF ) */
#endif
#endif
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