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# logb.m4 serial 2
dnl Copyright (C) 2010-2011 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_LOGB],
[
AC_REQUIRE([gl_MATH_H_DEFAULTS])
dnl Test whether logb() is declared.
AC_CHECK_DECLS([logb], , , [#include <math.h>])
if test "$ac_cv_have_decl_logb" != yes; then
HAVE_DECL_LOGB=0
fi
dnl Test whether logb() can be used without libm.
LOGB_LIBM=?
AC_LINK_IFELSE(
[AC_LANG_PROGRAM(
[[#ifndef __NO_MATH_INLINES
# define __NO_MATH_INLINES 1 /* for glibc */
#endif
#include <math.h>
extern double logb (double x);
double x;]],
[[x = logb(x);]])],
[LOGB_LIBM=])
if test "$LOGB_LIBM" = "?"; then
save_LIBS="$LIBS"
LIBS="$LIBS -lm"
AC_LINK_IFELSE(
[AC_LANG_PROGRAM(
[[#ifndef __NO_MATH_INLINES
# define __NO_MATH_INLINES 1 /* for glibc */
#endif
#include <math.h>
extern double logb (double x);
double x;]],
[[x = logb(x);]])],
[LOGB_LIBM="-lm"])
LIBS="$save_LIBS"
fi
if test "$LOGB_LIBM" = "?"; then
LOGB_LIBM=
fi
AC_SUBST([LOGB_LIBM])
])
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