# fpieee.m4 serial 2  -*- coding: utf-8 -*-

dnl Copyright (C) 2007, 2009-2019 Free Software Foundation, Inc.

dnl This file is free software; the Free Software Foundation

dnl gives unlimited permission to copy and/or distribute it,

dnl with or without modifications, as long as this notice is preserved.

dnl IEEE 754 standardized three items:

dnl - The formats of single-float and double-float - nowadays commonly

dnl   available as 'float' and 'double' in C and C++.

dnl   No autoconf test needed.

dnl - The overflow and division by zero behaviour: The result are values

dnl   '±Inf' and 'NaN', rather than exceptions as it was before.

dnl   This file provides an autoconf macro for ensuring this behaviour of

dnl   floating-point operations.

dnl - A set of conditions (overflow, underflow, inexact, etc.) which can

dnl   be configured to trigger an exception.

dnl   This cannot be done in a portable way: it depends on the compiler,

dnl   libc, kernel, and CPU.  No autoconf macro is provided for this.

dnl Ensure non-trapping behaviour of floating-point overflow and

dnl floating-point division by zero.

dnl (For integer overflow, see gcc's -ftrapv option; for integer division by

dnl zero, see the autoconf macro in intdiv0.m4.)

AC_DEFUN([gl_FP_IEEE],

[

  AC_REQUIRE([AC_PROG_CC])

  AC_REQUIRE([AC_CANONICAL_HOST])

  # IEEE behaviour is the default on all CPUs except Alpha and SH

  # (according to the test results of Bruno Haible's ieeefp/fenv_default.m4

  # and the GCC 4.1.2 manual).

  case "$host_cpu" in

    alpha*)

      # On Alpha systems, a compiler option provides the behaviour.

      # See the ieee(3) manual page, also available at

      # <https://backdrift.org/man/tru64/man3/ieee.3.html>

      if test -n "$GCC"; then

        # GCC has the option -mieee.

        # For full IEEE compliance (rarely needed), use option -mieee-with-inexact.

        CPPFLAGS="$CPPFLAGS -mieee"

      else

        # Compaq (ex-DEC) C has the option -ieee, equivalent to -ieee_with_no_inexact.

        # For full IEEE compliance (rarely needed), use option -ieee_with_inexact.

        CPPFLAGS="$CPPFLAGS -ieee"

      fi

      ;;

    sh*)

      if test -n "$GCC"; then

        # GCC has the option -mieee.

        CPPFLAGS="$CPPFLAGS -mieee"

      fi

      ;;

  esac

])