3 dnl Copyright (C) 2007, 2009-2024 Free Software Foundation, Inc.
4 dnl This file is free software; the Free Software Foundation
5 dnl gives unlimited permission to copy and/or distribute it,
6 dnl with or without modifications, as long as this notice is preserved.
8 dnl IEEE 754 standardized three items:
9 dnl - The formats of single-float and double-float - nowadays commonly
10 dnl available as 'float' and 'double' in C and C++.
11 dnl No autoconf test needed.
12 dnl - The overflow and division by zero behaviour: The result are values
13 dnl '±Inf' and 'NaN', rather than exceptions as it was before.
14 dnl This file provides an autoconf macro for ensuring this behaviour of
15 dnl floating-point operations.
16 dnl - A set of conditions (overflow, underflow, inexact, etc.) which can
17 dnl be configured to trigger an exception.
18 dnl This cannot be done in a portable way: it depends on the compiler,
19 dnl libc, kernel, and CPU. No autoconf macro is provided for this.
21 dnl Ensure non-trapping behaviour of floating-point overflow and
22 dnl floating-point division by zero.
23 dnl (For integer overflow, see gcc's -ftrapv option; for integer division by
24 dnl zero, see the autoconf macro in intdiv0.m4.)
26 AC_DEFUN([gl_FP_IEEE],
28 AC_REQUIRE([AC_PROG_CC])
29 AC_REQUIRE([AC_CANONICAL_HOST])
30 # IEEE behaviour is the default on all CPUs except Alpha and SH
31 # (according to the test results of Bruno Haible's ieeefp/fenv_default.m4
32 # and the GCC 4.1.2 manual).
35 # On Alpha systems, a compiler option provides the behaviour.
36 # See the ieee(3) manual page, also available at
37 # <https://backdrift.org/man/tru64/man3/ieee.3.html>
38 if test -n "$GCC"; then
39 # GCC has the option -mieee.
40 # For full IEEE compliance (rarely needed), use option -mieee-with-inexact.
41 CPPFLAGS="$CPPFLAGS -mieee"
43 # Compaq (ex-DEC) C has the option -ieee, equivalent to -ieee_with_no_inexact.
44 # For full IEEE compliance (rarely needed), use option -ieee_with_inexact.
45 CPPFLAGS="$CPPFLAGS -ieee"
49 if test -n "$GCC"; then
50 # GCC has the option -mieee.
51 CPPFLAGS="$CPPFLAGS -mieee"