-# signbit.m4 serial 1
-dnl Copyright (C) 2007 Free Software Foundation, Inc.
+# signbit.m4 serial 3
+dnl Copyright (C) 2007-2008 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_TRY_RUN([
#include <math.h>
+/* If signbit is defined as a function, don't use it, since calling it for
+ 'float' or 'long double' arguments would involve conversions.
+ If signbit is not declared at all but exists as a library function, don't
+ use it, since the prototype may not match.
+ If signbit is not declared at all but exists as a compiler built-in, don't
+ use it, since it's preferable to use __builtin_signbit* (no warnings,
+ no conversions). */
+#ifndef signbit
+# error "signbit should be a macro"
+#endif
#include <string.h>
+]gl_SIGNBIT_TEST_PROGRAM
+, [gl_cv_func_signbit=yes], [gl_cv_func_signbit=no],
+ [gl_cv_func_signbit="guessing no"])
+ ])
+ dnl GCC 4.0 and newer provides three built-ins for signbit.
+ dnl They can be used without warnings, also in C++, regardless of <math.h>.
+ dnl But they may expand to calls to functions, which may or may not be in
+ dnl libc.
+ AC_CACHE_CHECK([for signbit compiler built-ins], [gl_cv_func_signbit_gcc],
+ [
+ AC_TRY_RUN([
+#if __GNUC__ >= 4
+# define signbit(x) \
+ (sizeof (x) == sizeof (long double) ? __builtin_signbitl (x) : \
+ sizeof (x) == sizeof (double) ? __builtin_signbit (x) : \
+ __builtin_signbitf (x))
+#else
+# error "signbit should be three compiler built-ins"
+#endif
+#include <string.h>
+]gl_SIGNBIT_TEST_PROGRAM
+, [gl_cv_func_signbit_gcc=yes], [gl_cv_func_signbit_gcc=no],
+ [gl_cv_func_signbit_gcc="guessing no"])
+ ])
+ dnl Use the compiler built-ins whenever possible, because they are more
+ dnl efficient than the system library functions (if they exist).
+ if test "$gl_cv_func_signbit_gcc" = yes; then
+ REPLACE_SIGNBIT_USING_GCC=1
+ else
+ if test "$gl_cv_func_signbit" != yes; then
+ REPLACE_SIGNBIT=1
+ AC_LIBOBJ([signbitf])
+ AC_LIBOBJ([signbitd])
+ AC_LIBOBJ([signbitl])
+ gl_FLOAT_SIGN_LOCATION
+ gl_DOUBLE_SIGN_LOCATION
+ gl_LONG_DOUBLE_SIGN_LOCATION
+ if test "$gl_cv_cc_float_signbit" = unknown; then
+ dnl Test whether copysignf() is declared.
+ AC_CHECK_DECLS([copysignf], , , [#include <math.h>])
+ if test "$ac_cv_have_decl_copysignf" = yes; then
+ dnl Test whether copysignf() can be used without libm.
+ AC_CACHE_CHECK([whether copysignf can be used without linking with libm],
+ [gl_cv_func_copysignf_no_libm],
+ [
+ AC_TRY_LINK([#include <math.h>
+ float x, y;],
+ [return copysignf (x, y) < 0;],
+ [gl_cv_func_copysignf_no_libm=yes],
+ [gl_cv_func_copysignf_no_libm=no])
+ ])
+ if test $gl_cv_func_copysignf_no_libm = yes; then
+ AC_DEFINE([HAVE_COPYSIGNF_IN_LIBC], 1,
+ [Define if the copysignf function is declared in <math.h> and available in libc.])
+ fi
+ fi
+ fi
+ if test "$gl_cv_cc_double_signbit" = unknown; then
+ dnl Test whether copysign() is declared.
+ AC_CHECK_DECLS([copysign], , , [#include <math.h>])
+ if test "$ac_cv_have_decl_copysign" = yes; then
+ dnl Test whether copysign() can be used without libm.
+ AC_CACHE_CHECK([whether copysign can be used without linking with libm],
+ [gl_cv_func_copysign_no_libm],
+ [
+ AC_TRY_LINK([#include <math.h>
+ double x, y;],
+ [return copysign (x, y) < 0;],
+ [gl_cv_func_copysign_no_libm=yes],
+ [gl_cv_func_copysign_no_libm=no])
+ ])
+ if test $gl_cv_func_copysign_no_libm = yes; then
+ AC_DEFINE([HAVE_COPYSIGN_IN_LIBC], 1,
+ [Define if the copysign function is declared in <math.h> and available in libc.])
+ fi
+ fi
+ fi
+ if test "$gl_cv_cc_long_double_signbit" = unknown; then
+ dnl Test whether copysignl() is declared.
+ AC_CHECK_DECLS([copysignl], , , [#include <math.h>])
+ if test "$ac_cv_have_decl_copysignl" = yes; then
+ dnl Test whether copysignl() can be used without libm.
+ AC_CACHE_CHECK([whether copysignl can be used without linking with libm],
+ [gl_cv_func_copysignl_no_libm],
+ [
+ AC_TRY_LINK([#include <math.h>
+ long double x, y;],
+ [return copysignl (x, y) < 0;],
+ [gl_cv_func_copysignl_no_libm=yes],
+ [gl_cv_func_copysignl_no_libm=no])
+ ])
+ if test $gl_cv_func_copysignl_no_libm = yes; then
+ AC_DEFINE([HAVE_COPYSIGNL_IN_LIBC], 1,
+ [Define if the copysignl function is declared in <math.h> and available in libc.])
+ fi
+ fi
+ fi
+ fi
+ fi
+])
+
+AC_DEFUN([gl_SIGNBIT_TEST_PROGRAM], [
float p0f = 0.0f;
float m0f = -0.0f;
double p0d = 0.0;
return 1;
}
return 0;
-}], [gl_cv_func_signbit=yes], [gl_cv_func_signbit=no],
- [gl_cv_func_signbit="guessing no"])
- ])
- if test "$gl_cv_func_signbit" != yes; then
- REPLACE_SIGNBIT=1
- AC_LIBOBJ([signbitf])
- AC_LIBOBJ([signbitd])
- AC_LIBOBJ([signbitl])
- gl_FLOAT_SIGN_LOCATION
- gl_DOUBLE_SIGN_LOCATION
- gl_LONG_DOUBLE_SIGN_LOCATION
- fi
+}
])
AC_DEFUN([gl_FLOAT_SIGN_LOCATION],
projects / gnulib.git / blobdiff