> When cross-compiling, I also see this wrong guess:
>
> checking for signbit macro... guessing no
>
> This should fix it. (Most of this patch is merely reindentation.)
There is another wrong guess in the same file:
checking for signbit compiler built-ins... guessing no
This combined patch (modulo reindentation) fixes both.
2012-05-05 Bruno Haible <br...@clisp.org>
signbit: Avoid "guessing no" when cross-compiling to glibc systems.
* m4/signbit.m4 (gl_SIGNBIT): Require AC_CANONICAL_HOST. When cross-
compiling to a glibc system, set gl_cv_func_signbit and
gl_cv_func_signbit_gcc to "guessing yes".
diff --git a/m4/signbit.m4 b/m4/signbit.m4
index 8955326..e9877f6 100644
--- a/m4/signbit.m4
+++ b/m4/signbit.m4
@@ -1,4 +1,4 @@
-# signbit.m4 serial 11
+# signbit.m4 serial 12
dnl Copyright (C) 2007-2012 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
@@ -7,6 +7,7 @@ dnl with or without modifications, as long as this notice is
preserved.
AC_DEFUN([gl_SIGNBIT],
[
AC_REQUIRE([gl_MATH_H_DEFAULTS])
+ AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
AC_CACHE_CHECK([for signbit macro], [gl_cv_func_signbit],
[
AC_RUN_IFELSE(
@@ -27,7 +28,13 @@ AC_DEFUN([gl_SIGNBIT],
])],
[gl_cv_func_signbit=yes],
[gl_cv_func_signbit=no],
- [gl_cv_func_signbit="guessing no"])
+ [case "$host_os" in
+ # Guess yes on glibc systems.
+ *-gnu*) gl_cv_func_signbit="guessing yes" ;;
+ # If we don't know, assume the worst.
+ *) gl_cv_func_signbit="guessing no" ;;
+ esac
+ ])
])
dnl GCC 4.0 and newer provides three built-ins for signbit.
dnl They can be used without warnings, also in C++, regardless of <math.h>.
@@ -50,14 +57,24 @@ AC_DEFUN([gl_SIGNBIT],
])],
[gl_cv_func_signbit_gcc=yes],
[gl_cv_func_signbit_gcc=no],
- [gl_cv_func_signbit_gcc="guessing no"])
+ [case "$host_os" in
+ # Guess yes on glibc systems.
+ *-gnu*) gl_cv_func_signbit_gcc="guessing yes" ;;
+ # If we don't know, assume the worst.
+ *) gl_cv_func_signbit_gcc="guessing no" ;;
+ esac
+ ])
])
dnl Use the compiler built-ins whenever possible, because they are more
dnl efficient than the system library functions (if they exist).
- if test "$gl_cv_func_signbit_gcc" = yes; then
+ case "$gl_cv_func_signbit_gcc" in
+ *yes)
REPLACE_SIGNBIT_USING_GCC=1
- else
- if test "$gl_cv_func_signbit" != yes; then
+ ;;
+ *)
+ case "$gl_cv_func_signbit" in
+ *yes) ;;
+ *)
dnl REPLACE_SIGNBIT=1 makes sure the signbit[fdl] functions get built.
REPLACE_SIGNBIT=1
gl_FLOAT_SIGN_LOCATION
@@ -129,8 +146,10 @@ AC_DEFUN([gl_SIGNBIT],
fi
fi
fi
- fi
- fi
+ ;;
+ esac
+ ;;
+ esac
])
AC_DEFUN([gl_SIGNBIT_TEST_PROGRAM], [[
