configure.in in _math says
AC_CHECK_HEADERS(ieeefp.h fp_class.h floatingpoint.h)
and later does
#ifdef HAVE_FP_CLASS_H #include <fpclass.h> #endif
in the test for HAVE_WORKING_FPSETMASK. HAVE_FP_CLASS_H is not used at all in math.c. There is at least one thing wrong here, right?