2 dnl Copyright (C) 2012 Free Software Foundation, Inc.
3 dnl This file is free software; the Free Software Foundation
4 dnl gives unlimited permission to copy and/or distribute it,
5 dnl with or without modifications, as long as this notice is preserved.
7 AC_DEFUN([gl_FUNC_LOGBL],
9 AC_REQUIRE([gl_MATH_H_DEFAULTS])
10 AC_REQUIRE([gl_LONG_DOUBLE_VS_DOUBLE])
11 AC_REQUIRE([gl_FUNC_LOGB])
13 dnl Persuade glibc <math.h> to declare logbl().
14 AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
16 dnl Test whether logbl() exists and determine LOGBL_LIBM. We cannot assume
17 dnl that logbl(), if it exists, is defined in the same library as logb().
18 dnl This is not the case on AIX >= 5.2, Solaris >= 10.
19 gl_MATHFUNC([logbl], [long double], [(long double)])
20 if test $gl_cv_func_logbl_no_libm = yes \
21 || test $gl_cv_func_logbl_in_libm = yes; then
23 LIBS="$LIBS $LOGBL_LIBM"
26 case "$gl_cv_func_logbl_works" in
33 if test $HAVE_LOGBL = 0 || test $REPLACE_LOGBL = 1; then
34 dnl Find libraries needed to link lib/logbl.c.
35 if test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 1; then
36 LOGBL_LIBM="$LOGB_LIBM"
38 AC_REQUIRE([gl_FUNC_FREXPL])
39 AC_REQUIRE([gl_FUNC_ISNANL])
41 dnl Append $FREXPL_LIBM to LOGBL_LIBM, avoiding gratuitous duplicates.
42 case " $LOGBL_LIBM " in
43 *" $FREXPL_LIBM "*) ;;
44 *) LOGBL_LIBM="$LOGBL_LIBM $FREXPL_LIBM" ;;
46 dnl Append $ISNANL_LIBM to LOGBL_LIBM, avoiding gratuitous duplicates.
47 case " $LOGBL_LIBM " in
48 *" $ISNANL_LIBM "*) ;;
49 *) LOGBL_LIBM="$LOGBL_LIBM $ISNANL_LIBM" ;;
53 AC_SUBST([LOGBL_LIBM])
56 dnl Test whether logbl() works.
57 dnl On glibc 2.11/ppc, glibc 2.7/sparc, glibc 2.7/hppa, Solaris 10/SPARC, the
58 dnl return value for subnormal (denormalized) arguments is too large.
59 AC_DEFUN([gl_FUNC_LOGBL_WORKS],
61 AC_REQUIRE([AC_PROG_CC])
62 AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
63 AC_CACHE_CHECK([whether logbl works], [gl_cv_func_logbl_works],
69 /* Override the values of <float.h>, like done in float.in.h. */
70 #if defined __i386__ && (defined __BEOS__ || defined __OpenBSD__)
72 # define LDBL_MIN_EXP (-16381)
74 #if defined __i386__ && defined __FreeBSD__
76 # define LDBL_MIN_EXP (-16381)
78 #if (defined _ARCH_PPC || defined _POWER) && defined _AIX && (LDBL_MANT_DIG == 106) && defined __GNUC__
80 # define LDBL_MIN_EXP DBL_MIN_EXP
82 #if defined __sgi && (LDBL_MANT_DIG >= 106)
85 # define LDBL_MIN_EXP DBL_MIN_EXP
88 volatile long double x;
92 for (i = 1, x = 1.0L; i >= LDBL_MIN_EXP - 54; i--, x *= 0.5L)
93 /* Either x = 2^(i-1) or x = 0.0. */
94 if ((i == LDBL_MIN_EXP - 1 || i == LDBL_MIN_EXP - 54)
95 && (x > 0.0L && !(logbl (x) == (long double)(i - 1))))
100 [gl_cv_func_logbl_works=yes],
101 [gl_cv_func_logbl_works=no],
103 *gnu* | solaris*) gl_cv_func_logbl_works="guessing no";;
104 *) gl_cv_func_logbl_works="guessing yes";;