+dnl Test whether isnanf() can be used with libm.
+AC_DEFUN([gl_HAVE_ISNANF_IN_LIBM],
+[
+ AC_CACHE_CHECK([whether isnan(float) can be used with libm],
+ [gl_cv_func_isnanf_in_libm],
+ [
+ save_LIBS="$LIBS"
+ LIBS="$LIBS -lm"
+ AC_TRY_LINK([#include <math.h>
+ #if __GNUC__ >= 4
+ # undef isnanf
+ # define isnanf(x) __builtin_isnanf ((float)(x))
+ #elif defined isnan
+ # undef isnanf
+ # define isnanf(x) isnan ((float)(x))
+ #endif
+ float x;],
+ [return isnanf (x);],
+ [gl_cv_func_isnanf_in_libm=yes],
+ [gl_cv_func_isnanf_in_libm=no])
+ LIBS="$save_LIBS"
+ ])
+])
+
+dnl Test whether isnanf() rejects Infinity (this fails on Solaris 2.5.1),
+dnl recognizes a NaN (this fails on IRIX 6.5 with cc), and recognizes a NaN
+dnl with in-memory representation 0x7fbfffff (this fails on IRIX 6.5).
+AC_DEFUN([gl_ISNANF_WORKS],