Import ostree's compiler warnings, fix up callers

In ostree I maintain what I consider a "baseline" set of compiler
warnings that should *always* be fatal for a modern C project.

I noticed while working on a previous patch that a `-Werror=format`
warning wasn't fatal.

There are a few that are really, really important like
`-Werror=missing-prototypes`. I also take some like `-Werror=misleading-indentation`
which already caught some bugs.  See also https://lwn.net/Articles/678019/

10 files changed, 343 insertions, 25 deletions

diff --git a/.gitignore b/.gitignore
index 6e979cca..796332b4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -24,6 +24,7 @@ libtool
 ltmain.sh
 m4/*.m4
 !m4/glibtests.m4
+!m4/attributes.m4
 missing
 stamp-h1
 config.h.in
diff --git a/Makefile.am b/Makefile.am
index b1ec532e..2576d455 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -53,6 +53,8 @@ AM_CPPFLAGS =							\
 	-I$(builddir)/lib					\
 	$(NULL)
 
+AM_CFLAGS = $(WARN_CFLAGS)
+
 if WITH_SYSTEM_BWRAP
 AM_CPPFLAGS += -DHELPER=\"$(BWRAP)\"
 else
diff --git a/common/flatpak-dir.c b/common/flatpak-dir.c
index 70d49725..0d792799 100644
--- a/common/flatpak-dir.c
+++ b/common/flatpak-dir.c
@@ -576,7 +576,7 @@ flatpak_get_user_base_dir_location (void)
   return g_object_ref ((GFile *)file);
 }
 
-GFile *
+static GFile *
 flatpak_get_user_cache_dir_location (void)
 {
   g_autoptr(GFile) base_dir = NULL;
@@ -585,7 +585,7 @@ flatpak_get_user_cache_dir_location (void)
   return g_file_get_child (base_dir, "system-cache");
 }
 
-GFile *
+static GFile *
 flatpak_ensure_user_cache_dir_location (GError **error)
 {
   g_autoptr(GFile) cache_dir = NULL;
@@ -603,7 +603,7 @@ flatpak_ensure_user_cache_dir_location (GError **error)
   return g_steal_pointer (&cache_dir);
 }
 
-GFile *
+static GFile *
 flatpak_ensure_oci_summary_cache_dir_location (GError **error)
 {
   g_autoptr(GFile) cache_dir = NULL;
@@ -658,7 +658,7 @@ flatpak_dir_get_system_helper (FlatpakDir *self)
   return NULL;
 }
 
-gboolean
+static gboolean
 flatpak_dir_use_system_helper (FlatpakDir *self,
                                const char *installing_from_remote)
 {
@@ -2921,7 +2921,7 @@ out:
   return ret;
 }
 
-gboolean
+static gboolean
 flatpak_dir_run_triggers (FlatpakDir   *self,
                           GCancellable *cancellable,
                           GError      **error)
@@ -3349,7 +3349,7 @@ out:
   return ret;
 }
 
-gboolean
+static gboolean
 flatpak_rewrite_export_dir (const char   *app,
                             const char   *branch,
                             const char   *arch,
@@ -3467,7 +3467,7 @@ out:
   return ret;
 }
 
-gboolean
+static gboolean
 flatpak_export_dir (GFile        *source,
                     GFile        *destination,
                     const char   *symlink_prefix,
@@ -6146,7 +6146,7 @@ find_matching_ref (GHashTable *refs,
                                             parts[3]));
         }
 
-      flatpak_fail (error, err->str);
+      flatpak_fail (error, "%s", err->str);
       return NULL;
     }
 
@@ -6606,7 +6606,7 @@ flatpak_dir_remote_has_deploys (FlatpakDir   *self,
   return FALSE;
 }
 
-gint
+static gint
 cmp_remote (gconstpointer a,
             gconstpointer b,
             gpointer      user_data)
diff --git a/common/flatpak-run.c b/common/flatpak-run.c
index 8b734f8a..3fb58a3c 100644
--- a/common/flatpak-run.c
+++ b/common/flatpak-run.c
@@ -497,7 +497,7 @@ flatpak_context_set_system_bus_policy (FlatpakContext *context,
   g_hash_table_insert (context->system_bus_policy, g_strdup (name), GINT_TO_POINTER (policy));
 }
 
-void
+static void
 flatpak_context_apply_generic_policy (FlatpakContext *context,
                                       const char     *key,
                                       const char     *value)
@@ -2075,7 +2075,7 @@ create_proxy_socket (char *template)
   return g_steal_pointer (&proxy_socket);
 }
 
-gboolean
+static gboolean
 flatpak_run_add_system_dbus_args (FlatpakContext *context,
                                   char         ***envp_p,
                                   GPtrArray      *argv_array,
@@ -2127,7 +2127,7 @@ flatpak_run_add_system_dbus_args (FlatpakContext *context,
   return FALSE;
 }
 
-gboolean
+static gboolean
 flatpak_run_add_session_dbus_args (GPtrArray *argv_array,
                                    char    ***envp_p,
                                    GPtrArray *dbus_proxy_argv,
@@ -3487,7 +3487,7 @@ add_document_portal_args (GPtrArray  *argv_array,
     }
 }
 
-gchar *
+static gchar *
 join_args (GPtrArray *argv_array, gsize *len_out)
 {
   gchar *string;
diff --git a/common/flatpak-utils.c b/common/flatpak-utils.c
index c5f006bb..c6d122ea 100644
--- a/common/flatpak-utils.c
+++ b/common/flatpak-utils.c
@@ -285,7 +285,7 @@ flatpak_path_match_prefix (const char *pattern,
   return NULL; /* Should not be reached */
 }
 
-const char *
+static const char *
 flatpak_get_kernel_arch (void)
 {
   static struct utsname buf;
@@ -858,7 +858,7 @@ flatpak_kinds_from_bools (gboolean app, gboolean runtime)
   return kinds;
 }
 
-gboolean
+static gboolean
 _flatpak_split_partial_ref_arg (const char   *partial_ref,
                                 gboolean      validate,
                                 FlatpakKinds  default_kinds,
@@ -4695,9 +4695,13 @@ flatpak_yes_no_prompt (const char *prompt, ...)
   va_list var_args;
   gchar *s;
 
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat-nonliteral"
   va_start (var_args, prompt);
   s = g_strdup_vprintf (prompt, var_args);
   va_end (var_args);
+#pragma GCC diagnostic pop
 
   while (TRUE)
     {
@@ -5098,9 +5102,12 @@ flatpak_complete_word (FlatpakCompletion *completion,
 
   g_return_if_fail (format != NULL);
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat-nonliteral"
   va_start (args, format);
   string = g_strdup_vprintf (format, args);
   va_end (args);
+#pragma GCC diagnostic pop
 
   if (!g_str_has_prefix (string, completion->cur))
     return;
@@ -5144,7 +5151,7 @@ flatpak_complete_ref (FlatpakCompletion *completion,
     }
 }
 
-int
+static int
 find_current_element (const char *str)
 {
   int count = 0;
diff --git a/common/flatpak-utils.h b/common/flatpak-utils.h
index 96e42204..36ffb30b 100644
--- a/common/flatpak-utils.h
+++ b/common/flatpak-utils.h
@@ -579,8 +579,8 @@ gboolean flatpak_allocate_tmpdir (int           tmpdir_dfd,
                                   GError      **error);
 
 
-gboolean flatpak_yes_no_prompt (const char *prompt, ...);
-long flatpak_number_prompt (int min, int max, const char *prompt, ...);
+gboolean flatpak_yes_no_prompt (const char *prompt, ...) G_GNUC_PRINTF(1, 2);
+long flatpak_number_prompt (int min, int max, const char *prompt, ...) G_GNUC_PRINTF(3, 4);
 
 typedef void (*FlatpakLoadUriProgress) (guint64 downloaded_bytes,
                                         gpointer user_data);
@@ -621,7 +621,7 @@ FlatpakCompletion *flatpak_completion_new   (const char        *arg_line,
                                              const char        *arg_cur);
 void               flatpak_complete_word    (FlatpakCompletion *completion,
                                              char              *format,
-                                             ...);
+                                             ...) G_GNUC_PRINTF(2,3);
 void               flatpak_complete_ref     (FlatpakCompletion *completion,
                                              OstreeRepo        *repo);
 void               flatpak_complete_partial_ref (FlatpakCompletion *completion,
diff --git a/configure.ac b/configure.ac
index c9c08448..fdd73fb2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -55,12 +55,26 @@ AC_DEFINE_UNQUOTED(GETTEXT_PACKAGE, "$PACKAGE", [gettext domain])
 AM_SILENT_RULES([yes])
 AM_MAINTAINER_MODE([enable])
 
-if test "x$GCC" = "xyes"; then
-  case " $CFLAGS " in
-  *[[\ \	]]-Wall[[\ \	]]*) ;;
-  *) CFLAGS="$CFLAGS -Wall" ;;
-  esac
-fi
+dnl This list is shared with https://github.com/ostreedev/ostree
+CC_CHECK_FLAGS_APPEND([WARN_CFLAGS], [CFLAGS], [\
+-pipe \
+-Wall \
+-Werror=empty-body \
+-Werror=strict-prototypes \
+-Werror=missing-prototypes \
+-Werror=implicit-function-declaration \
+"-Werror=format=2 -Werror=format-security -Werror=format-nonliteral" \
+-Werror=pointer-arith -Werror=init-self \
+-Werror=missing-declarations \
+-Werror=return-type \
+-Werror=overflow \
+-Werror=int-conversion \
+-Werror=parenthesis \
+-Werror=incompatible-pointer-types \
+-Werror=misleading-indentation \
+-Werror=missing-include-dirs -Werror=aggregate-return \
+])
+AC_SUBST(WARN_CFLAGS)
 
 AX_VALGRIND_CHECK
 
diff --git a/lib/flatpak-installed-ref.c b/lib/flatpak-installed-ref.c
index ed830d66..6d1f3268 100644
--- a/lib/flatpak-installed-ref.c
+++ b/lib/flatpak-installed-ref.c
@@ -24,6 +24,7 @@
 
 #include "flatpak-utils.h"
 #include "flatpak-installed-ref.h"
+#include "flatpak-installed-ref-private.h"
 #include "flatpak-enum-types.h"
 
 /**
diff --git a/lib/flatpak-related-ref.c b/lib/flatpak-related-ref.c
index cf5216f2..133b4f66 100644
--- a/lib/flatpak-related-ref.c
+++ b/lib/flatpak-related-ref.c
@@ -24,6 +24,7 @@
 
 #include "flatpak-utils.h"
 #include "flatpak-related-ref.h"
+#include "flatpak-related-ref-private.h"
 #include "flatpak-enum-types.h"
 
 /**
diff --git a/m4/attributes.m4 b/m4/attributes.m4
new file mode 100644
index 00000000..51ac88be
--- /dev/null
+++ b/m4/attributes.m4
@@ -0,0 +1,292 @@
+dnl Macros to check the presence of generic (non-typed) symbols.
+dnl Copyright (c) 2006-2008 Diego Pettenò <flameeyes@gmail.com>
+dnl Copyright (c) 2006-2008 xine project
+dnl Copyright (c) 2012 Lucas De Marchi <lucas.de.marchi@gmail.com>
+dnl
+dnl This program is free software; you can redistribute it and/or modify
+dnl it under the terms of the GNU General Public License as published by
+dnl the Free Software Foundation; either version 2, or (at your option)
+dnl any later version.
+dnl
+dnl This program is distributed in the hope that it will be useful,
+dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
+dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+dnl GNU General Public License for more details.
+dnl
+dnl You should have received a copy of the GNU General Public License
+dnl along with this program; if not, write to the Free Software
+dnl Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+dnl 02110-1301, USA.
+dnl
+dnl As a special exception, the copyright owners of the
+dnl macro gives unlimited permission to copy, distribute and modify the
+dnl configure scripts that are the output of Autoconf when processing the
+dnl Macro. You need not follow the terms of the GNU General Public
+dnl License when using or distributing such scripts, even though portions
+dnl of the text of the Macro appear in them. The GNU General Public
+dnl License (GPL) does govern all other use of the material that
+dnl constitutes the Autoconf Macro.
+dnl
+dnl This special exception to the GPL applies to versions of the
+dnl Autoconf Macro released by this project. When you make and
+dnl distribute a modified version of the Autoconf Macro, you may extend
+dnl this special exception to the GPL to apply to your modified version as
+dnl well.
+
+dnl Check if FLAG in ENV-VAR is supported by compiler and append it
+dnl to WHERE-TO-APPEND variable. Note that we invert -Wno-* checks to
+dnl -W* as gcc cannot test for negated warnings. If a C snippet is passed,
+dnl use it, otherwise use a simple main() definition that just returns 0.
+dnl CC_CHECK_FLAG_APPEND([WHERE-TO-APPEND], [ENV-VAR], [FLAG], [C-SNIPPET])
+
+AC_DEFUN([CC_CHECK_FLAG_APPEND], [
+  AC_CACHE_CHECK([if $CC supports flag $3 in envvar $2],
+                 AS_TR_SH([cc_cv_$2_$3]),
+          [eval "AS_TR_SH([cc_save_$2])='${$2}'"
+           eval "AS_TR_SH([$2])='${cc_save_$2} -Werror `echo "$3" | sed 's/^-Wno-/-W/'`'"
+           AC_LINK_IFELSE([AC_LANG_SOURCE(ifelse([$4], [],
+                                                 [int main(void) { return 0; } ],
+                                                 [$4]))],
+                          [eval "AS_TR_SH([cc_cv_$2_$3])='yes'"],
+                          [eval "AS_TR_SH([cc_cv_$2_$3])='no'"])
+           eval "AS_TR_SH([$2])='$cc_save_$2'"])
+
+  AS_IF([eval test x$]AS_TR_SH([cc_cv_$2_$3])[ = xyes],
+        [eval "$1='${$1} $3'"])
+])
+
+dnl CC_CHECK_FLAGS_APPEND([WHERE-TO-APPEND], [ENV-VAR], [FLAG1 FLAG2], [C-SNIPPET])
+AC_DEFUN([CC_CHECK_FLAGS_APPEND], [
+  for flag in [$3]; do
+    CC_CHECK_FLAG_APPEND([$1], [$2], $flag, [$4])
+  done
+])
+
+dnl Check if the flag is supported by linker (cacheable)
+dnl CC_CHECK_LDFLAGS([FLAG], [ACTION-IF-FOUND],[ACTION-IF-NOT-FOUND])
+
+AC_DEFUN([CC_CHECK_LDFLAGS], [
+  AC_CACHE_CHECK([if $CC supports $1 flag],
+    AS_TR_SH([cc_cv_ldflags_$1]),
+    [ac_save_LDFLAGS="$LDFLAGS"
+     LDFLAGS="$LDFLAGS $1"
+     AC_LINK_IFELSE([int main() { return 1; }],
+       [eval "AS_TR_SH([cc_cv_ldflags_$1])='yes'"],
+       [eval "AS_TR_SH([cc_cv_ldflags_$1])="])
+     LDFLAGS="$ac_save_LDFLAGS"
+    ])
+
+  AS_IF([eval test x$]AS_TR_SH([cc_cv_ldflags_$1])[ = xyes],
+    [$2], [$3])
+])
+
+dnl define the LDFLAGS_NOUNDEFINED variable with the correct value for
+dnl the current linker to avoid undefined references in a shared object.
+AC_DEFUN([CC_NOUNDEFINED], [
+  dnl We check $host for which systems to enable this for.
+  AC_REQUIRE([AC_CANONICAL_HOST])
+
+  case $host in
+     dnl FreeBSD (et al.) does not complete linking for shared objects when pthreads
+     dnl are requested, as different implementations are present; to avoid problems
+     dnl use -Wl,-z,defs only for those platform not behaving this way.
+     *-freebsd* | *-openbsd*) ;;
+     *)
+        dnl First of all check for the --no-undefined variant of GNU ld. This allows
+        dnl for a much more readable command line, so that people can understand what
+        dnl it does without going to look for what the heck -z defs does.
+        for possible_flags in "-Wl,--no-undefined" "-Wl,-z,defs"; do
+           CC_CHECK_LDFLAGS([$possible_flags], [LDFLAGS_NOUNDEFINED="$possible_flags"])
+           break
+        done
+     ;;
+  esac
+
+  AC_SUBST([LDFLAGS_NOUNDEFINED])
+])
+
+dnl Check for a -Werror flag or equivalent. -Werror is the GCC
+dnl and ICC flag that tells the compiler to treat all the warnings
+dnl as fatal. We usually need this option to make sure that some
+dnl constructs (like attributes) are not simply ignored.
+dnl
+dnl Other compilers don't support -Werror per se, but they support
+dnl an equivalent flag:
+dnl  - Sun Studio compiler supports -errwarn=%all
+AC_DEFUN([CC_CHECK_WERROR], [
+  AC_CACHE_CHECK(
+    [for $CC way to treat warnings as errors],
+    [cc_cv_werror],
+    [CC_CHECK_CFLAGS_SILENT([-Werror], [cc_cv_werror=-Werror],
+      [CC_CHECK_CFLAGS_SILENT([-errwarn=%all], [cc_cv_werror=-errwarn=%all])])
+    ])
+])
+
+AC_DEFUN([CC_CHECK_ATTRIBUTE], [
+  AC_REQUIRE([CC_CHECK_WERROR])
+  AC_CACHE_CHECK([if $CC supports __attribute__(( ifelse([$2], , [$1], [$2]) ))],
+    AS_TR_SH([cc_cv_attribute_$1]),
+    [ac_save_CFLAGS="$CFLAGS"
+     CFLAGS="$CFLAGS $cc_cv_werror"
+     AC_COMPILE_IFELSE([AC_LANG_SOURCE([$3])],
+       [eval "AS_TR_SH([cc_cv_attribute_$1])='yes'"],
+       [eval "AS_TR_SH([cc_cv_attribute_$1])='no'"])
+     CFLAGS="$ac_save_CFLAGS"
+    ])
+
+  AS_IF([eval test x$]AS_TR_SH([cc_cv_attribute_$1])[ = xyes],
+    [AC_DEFINE(
+       AS_TR_CPP([SUPPORT_ATTRIBUTE_$1]), 1,
+         [Define this if the compiler supports __attribute__(( ifelse([$2], , [$1], [$2]) ))]
+         )
+     $4],
+    [$5])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_CONSTRUCTOR], [
+  CC_CHECK_ATTRIBUTE(
+    [constructor],,
+    [void __attribute__((constructor)) ctor() { int a; }],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_FORMAT], [
+  CC_CHECK_ATTRIBUTE(
+    [format], [format(printf, n, n)],
+    [void __attribute__((format(printf, 1, 2))) printflike(const char *fmt, ...) { fmt = (void *)0; }],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_FORMAT_ARG], [
+  CC_CHECK_ATTRIBUTE(
+    [format_arg], [format_arg(printf)],
+    [char *__attribute__((format_arg(1))) gettextlike(const char *fmt) { fmt = (void *)0; }],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_VISIBILITY], [
+  CC_CHECK_ATTRIBUTE(
+    [visibility_$1], [visibility("$1")],
+    [void __attribute__((visibility("$1"))) $1_function() { }],
+    [$2], [$3])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_NONNULL], [
+  CC_CHECK_ATTRIBUTE(
+    [nonnull], [nonnull()],
+    [void __attribute__((nonnull())) some_function(void *foo, void *bar) { foo = (void*)0; bar = (void*)0; }],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_UNUSED], [
+  CC_CHECK_ATTRIBUTE(
+    [unused], ,
+    [void some_function(void *foo, __attribute__((unused)) void *bar);],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_SENTINEL], [
+  CC_CHECK_ATTRIBUTE(
+    [sentinel], ,
+    [void some_function(void *foo, ...) __attribute__((sentinel));],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_DEPRECATED], [
+  CC_CHECK_ATTRIBUTE(
+    [deprecated], ,
+    [void some_function(void *foo, ...) __attribute__((deprecated));],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_ALIAS], [
+  CC_CHECK_ATTRIBUTE(
+    [alias], [weak, alias],
+    [void other_function(void *foo) { }
+     void some_function(void *foo) __attribute__((weak, alias("other_function")));],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_MALLOC], [
+  CC_CHECK_ATTRIBUTE(
+    [malloc], ,
+    [void * __attribute__((malloc)) my_alloc(int n);],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_PACKED], [
+  CC_CHECK_ATTRIBUTE(
+    [packed], ,
+    [struct astructure { char a; int b; long c; void *d; } __attribute__((packed));],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_CONST], [
+  CC_CHECK_ATTRIBUTE(
+    [const], ,
+    [int __attribute__((const)) twopow(int n) { return 1 << n; } ],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_FLAG_VISIBILITY], [
+  AC_REQUIRE([CC_CHECK_WERROR])
+  AC_CACHE_CHECK([if $CC supports -fvisibility=hidden],
+    [cc_cv_flag_visibility],
+    [cc_flag_visibility_save_CFLAGS="$CFLAGS"
+     CFLAGS="$CFLAGS $cc_cv_werror"
+     CC_CHECK_CFLAGS_SILENT([-fvisibility=hidden],
+     cc_cv_flag_visibility='yes',
+     cc_cv_flag_visibility='no')
+     CFLAGS="$cc_flag_visibility_save_CFLAGS"])
+
+  AS_IF([test "x$cc_cv_flag_visibility" = "xyes"],
+    [AC_DEFINE([SUPPORT_FLAG_VISIBILITY], 1,
+       [Define this if the compiler supports the -fvisibility flag])
+     $1],
+    [$2])
+])
+
+AC_DEFUN([CC_FUNC_EXPECT], [
+  AC_REQUIRE([CC_CHECK_WERROR])
+  AC_CACHE_CHECK([if compiler has __builtin_expect function],
+    [cc_cv_func_expect],
+    [ac_save_CFLAGS="$CFLAGS"
+     CFLAGS="$CFLAGS $cc_cv_werror"
+     AC_COMPILE_IFELSE([AC_LANG_SOURCE(
+       [int some_function() {
+        int a = 3;
+        return (int)__builtin_expect(a, 3);
+     }])],
+       [cc_cv_func_expect=yes],
+       [cc_cv_func_expect=no])
+     CFLAGS="$ac_save_CFLAGS"
+    ])
+
+  AS_IF([test "x$cc_cv_func_expect" = "xyes"],
+    [AC_DEFINE([SUPPORT__BUILTIN_EXPECT], 1,
+     [Define this if the compiler supports __builtin_expect() function])
+     $1],
+    [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_ALIGNED], [
+  AC_REQUIRE([CC_CHECK_WERROR])
+  AC_CACHE_CHECK([highest __attribute__ ((aligned ())) supported],
+    [cc_cv_attribute_aligned],
+    [ac_save_CFLAGS="$CFLAGS"
+     CFLAGS="$CFLAGS $cc_cv_werror"
+     for cc_attribute_align_try in 64 32 16 8 4 2; do
+        AC_COMPILE_IFELSE([AC_LANG_SOURCE([
+          int main() {
+            static char c __attribute__ ((aligned($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
+])