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# log2.m4 serial 10
dnl Copyright (C) 2010-2020 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.
AC_DEFUN([gl_FUNC_LOG2],
[
m4_divert_text([DEFAULTS], [gl_log2_required=plain])
AC_REQUIRE([gl_MATH_H_DEFAULTS])
dnl Persuade glibc <math.h> to declare log2().
AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
dnl Determine LOG2_LIBM.
gl_COMMON_DOUBLE_MATHFUNC([log2])
dnl Test whether log2() exists.
save_LIBS="$LIBS"
LIBS="$LIBS $LOG2_LIBM"
AC_CHECK_FUNCS([log2])
LIBS="$save_LIBS"
if test $ac_cv_func_log2 = yes; then
HAVE_LOG2=1
dnl Also check whether it's declared.
dnl IRIX 6.5 has log2() in libm but doesn't declare it in <math.h>.
AC_CHECK_DECL([log2], , [HAVE_DECL_LOG2=0], [[#include <math.h>]])
save_LIBS="$LIBS"
LIBS="$LIBS $LOG2_LIBM"
gl_FUNC_LOG2_WORKS
LIBS="$save_LIBS"
case "$gl_cv_func_log2_works" in
*yes) ;;
*) REPLACE_LOG2=1 ;;
esac
m4_ifdef([gl_FUNC_LOG2_IEEE], [
if test $gl_log2_required = ieee && test $REPLACE_LOG2 = 0; then
AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
AC_CACHE_CHECK([whether log2 works according to ISO C 99 with IEC 60559],
[gl_cv_func_log2_ieee],
[
save_LIBS="$LIBS"
LIBS="$LIBS $LOG2_LIBM"
AC_RUN_IFELSE(
[AC_LANG_SOURCE([[
#ifndef __NO_MATH_INLINES
# define __NO_MATH_INLINES 1 /* for glibc */
#endif
#include <math.h>
#ifndef log2 /* for Cygwin 1.7.x */
extern
#ifdef __cplusplus
"C"
#endif
double log2 (double);
#endif
/* Compare two numbers with ==.
This is a separate function because IRIX 6.5 "cc -O" miscompiles an
'x == x' test. */
static int
numeric_equal (double x, double y)
{
return x == y;
}
static double dummy (double x) { return 0; }
int main (int argc, char *argv[])
{
double (* volatile my_log2) (double) = argc ? log2 : dummy;
/* Test log2(negative).
This test fails on NetBSD 5.1 and Solaris 10/x86_64. */
double y = my_log2 (-1.0);
if (numeric_equal (y, y))
return 1;
return 0;
}
]])],
[gl_cv_func_log2_ieee=yes],
[gl_cv_func_log2_ieee=no],
[case "$host_os" in
# Guess yes on glibc systems.
*-gnu* | gnu*) gl_cv_func_log2_ieee="guessing yes" ;;
# Guess yes on musl systems.
*-musl*) gl_cv_func_log2_ieee="guessing yes" ;;
# Guess yes on native Windows.
mingw*) gl_cv_func_log2_ieee="guessing yes" ;;
# If we don't know, obey --enable-cross-guesses.
*) gl_cv_func_log2_ieee="$gl_cross_guess_normal" ;;
esac
])
LIBS="$save_LIBS"
])
case "$gl_cv_func_log2_ieee" in
*yes) ;;
*) REPLACE_LOG2=1 ;;
esac
fi
])
else
HAVE_LOG2=0
HAVE_DECL_LOG2=0
fi
if test $HAVE_LOG2 = 0 || test $REPLACE_LOG2 = 1; then
dnl Find libraries needed to link lib/log2.c.
AC_REQUIRE([gl_FUNC_ISNAND])
AC_REQUIRE([gl_FUNC_FREXP])
AC_REQUIRE([gl_FUNC_LOG])
LOG2_LIBM=
dnl Append $ISNAND_LIBM to LOG2_LIBM, avoiding gratuitous duplicates.
case " $LOG2_LIBM " in
*" $ISNAND_LIBM "*) ;;
*) LOG2_LIBM="$LOG2_LIBM $ISNAND_LIBM" ;;
esac
dnl Append $FREXP_LIBM to LOG2_LIBM, avoiding gratuitous duplicates.
case " $LOG2_LIBM " in
*" $FREXP_LIBM "*) ;;
*) LOG2_LIBM="$LOG2_LIBM $FREXP_LIBM" ;;
esac
dnl Append $LOG_LIBM to LOG2_LIBM, avoiding gratuitous duplicates.
case " $LOG2_LIBM " in
*" $LOG_LIBM "*) ;;
*) LOG2_LIBM="$LOG2_LIBM $LOG_LIBM" ;;
esac
fi
])
dnl Test whether log2() works.
dnl On OSF/1 5.1, log2(-0.0) is NaN.
dnl On Cygwin 1.7.9, log2(2^29) is not exactly 29.
AC_DEFUN([gl_FUNC_LOG2_WORKS],
[
AC_REQUIRE([AC_PROG_CC])
AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
AC_CACHE_CHECK([whether log2 works], [gl_cv_func_log2_works],
[
AC_RUN_IFELSE(
[AC_LANG_SOURCE([[
#include <math.h>
#ifndef log2 /* for Cygwin 1.7.x */
extern
#ifdef __cplusplus
"C"
#endif
double log2 (double);
#endif
volatile double x;
volatile double y;
int main ()
{
int result = 0;
/* This test fails on OSF/1 5.1. */
x = -0.0;
y = log2 (x);
if (!(y + y == y))
result |= 1;
/* This test fails on Cygwin 1.7.9. */
x = 536870912.0;
y = log2 (x);
if (!(y == 29.0))
result |= 2;
return result;
}
]])],
[gl_cv_func_log2_works=yes],
[gl_cv_func_log2_works=no],
[case "$host_os" in
cygwin* | osf*) gl_cv_func_log2_works="guessing no" ;;
# Guess yes on native Windows.
mingw*) gl_cv_func_log2_works="guessing yes" ;;
*) gl_cv_func_log2_works="guessing yes" ;;
esac
])
])
])
|
