1# fpieee.m4 serial 2  -*- coding: utf-8 -*-
2dnl Copyright (C) 2007, 2009-2020 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7dnl IEEE 754 standardized three items:
8dnl - The formats of single-float and double-float - nowadays commonly
9dnl   available as 'float' and 'double' in C and C++.
10dnl   No autoconf test needed.
11dnl - The overflow and division by zero behaviour: The result are values
12dnl   '±Inf' and 'NaN', rather than exceptions as it was before.
13dnl   This file provides an autoconf macro for ensuring this behaviour of
14dnl   floating-point operations.
15dnl - A set of conditions (overflow, underflow, inexact, etc.) which can
16dnl   be configured to trigger an exception.
17dnl   This cannot be done in a portable way: it depends on the compiler,
18dnl   libc, kernel, and CPU.  No autoconf macro is provided for this.
19
20dnl Ensure non-trapping behaviour of floating-point overflow and
21dnl floating-point division by zero.
22dnl (For integer overflow, see gcc's -ftrapv option; for integer division by
23dnl zero, see the autoconf macro in intdiv0.m4.)
24
25AC_DEFUN([gl_FP_IEEE],
26[
27  AC_REQUIRE([AC_PROG_CC])
28  AC_REQUIRE([AC_CANONICAL_HOST])
29  # IEEE behaviour is the default on all CPUs except Alpha and SH
30  # (according to the test results of Bruno Haible's ieeefp/fenv_default.m4
31  # and the GCC 4.1.2 manual).
32  case "$host_cpu" in
33    alpha*)
34      # On Alpha systems, a compiler option provides the behaviour.
35      # See the ieee(3) manual page, also available at
36      # <https://backdrift.org/man/tru64/man3/ieee.3.html>
37      if test -n "$GCC"; then
38        # GCC has the option -mieee.
39        # For full IEEE compliance (rarely needed), use option -mieee-with-inexact.
40        CPPFLAGS="$CPPFLAGS -mieee"
41      else
42        # Compaq (ex-DEC) C has the option -ieee, equivalent to -ieee_with_no_inexact.
43        # For full IEEE compliance (rarely needed), use option -ieee_with_inexact.
44        CPPFLAGS="$CPPFLAGS -ieee"
45      fi
46      ;;
47    sh*)
48      if test -n "$GCC"; then
49        # GCC has the option -mieee.
50        CPPFLAGS="$CPPFLAGS -mieee"
51      fi
52      ;;
53  esac
54])
55