The AC_C_ATTRIBUTE_ALIGNED macro is broken, it always reports maximum aligned available as 64 even on Darwin where the maximum is 16, as it does not use -Werror, and the wrong alignment is considered only a warning. Rewrite it as CC_ATTRIBUTE_ALIGNED (in attributes.m4, where other similar macros are located). Also reverse the order of the checks, so that the highest version is tried first; this way you can avoid five compile tests on systems where 64 is the highest alignment available.

CVS patchset: 8726
CVS date: 2007/03/20 00:30:55

1 files changed, 22 insertions, 0 deletions

diff --git a/m4/attributes.m4 b/m4/attributes.m4
index 28e2e5839..2d52cebc4 100644
--- a/m4/attributes.m4
+++ b/m4/attributes.m4
@@ -305,3 +305,25 @@ AC_DEFUN([CC_ATTRIBUTE_ALIAS], [
 		$2
 	fi
 ])
+
+AC_DEFUN([CC_ATTRIBUTE_ALIGNED], [
+  AC_REQUIRE([CC_CHECK_WERROR])
+  AC_CACHE_CHECK([highest __attribute__ ((aligned ())) supported],
+    [cc_cv_attribute_aligned],
+    [ac_save_CFLAGS="$CFLAGS"
+     CFLAGS="$CFLAGS $cc_cv_werror"
+     for cc_attribute_align_try in 64 32 16 8 4 2; do
+        AC_COMPILE_IFELSE([
+          int main() {
+            static char c __attribute__ ((aligned($cc_attribute_align_try))) = 0;
+            return c;
+          }], [cc_cv_attribute_aligned=$cc_attribute_align_try; break])
+     done
+     CFLAGS="$ac_save_CFLAGS"
+  ])
+
+  if test "x$cc_cv_attribute_aligned" != "x"; then
+     AC_DEFINE_UNQUOTED([ATTRIBUTE_ALIGNED_MAX], [$cc_cv_attribute_aligned],
+       [Define the highest alignment supported])
+  fi
+])