[PATCH] fixup libobjc usage of PCC_BITFIELD_TYPE_MATTERS

[tbsaunde+gcc@tbsaunde.org]

From: Trevor Saunders <tbsaunde+gcc@tbsaunde.org>

Hi,

This adds a configure check to libobjc to find out if types of bitfields effect
their layout, and uses it to replace the rather broken usage of
PCC_BITFIELD_TYPE_MATTERS.

bootstrapped + regtested x86_64-linux-gnu, bootstrapped on ppc64le-linux-gnu
and ran check-objc there without failures, and checked the correct part of the
ifdef is used on a cross to m68k-linux-elf.  ok?  I'm sure I've gotten
something wrong since this is a bunch of auto tools ;-)

Trev

libobjc/ChangeLog:

2015-05-01  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>

	* acinclude.m4: Include bitfields.m4.
	* config.h.in: Regenerate.
	* configure: Likewise.
	* configure.ac: Invoke gt_BITFIELD_TYPE_MATTERS.
	* encoding.c: Check HAVE_BITFIELD_TYPE_MATTERS.

config/ChangeLog:

2015-05-01  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>

	* bitfields.m4: New file.
---
 config/bitfields.m4  | 26 ++++++++++++++++++++++++++
 libobjc/acinclude.m4 |  1 +
 libobjc/config.h.in  |  3 +++
 libobjc/configure    | 38 ++++++++++++++++++++++++++++++++++++++
 libobjc/configure.ac |  2 ++
 libobjc/encoding.c   |  3 ++-
 6 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 config/bitfields.m4

diff --git a/config/bitfields.m4 b/config/bitfields.m4
new file mode 100644
index 0000000..ee8f3b5
--- /dev/null
+++ b/config/bitfields.m4
@@ -0,0 +1,26 @@
+dnl Copyright (C) 2015 Free Software Foundation, Inc.
+dnl This file is free software, distributed under the terms of the GNU
+dnl General Public License.  As a special exception to the GNU General
+dnl Public License, this file may be distributed as part of a program
+dnl that contains a configuration script generated by Autoconf, under
+dnl the same distribution terms as the rest of that program.
+
+# Define HAVE_BITFIELD_TYPE_MATTERS if the type of bitfields effects their
+# alignment.
+
+AC_DEFUN([gt_BITFIELD_TYPE_MATTERS],
+[
+  AC_CACHE_CHECK([if the type of bitfields matters], gt_cv_bitfield_type_matters,
+  [
+    AC_TRY_COMPILE(
+      [struct foo1 { char x; char :0; char y; };
+struct foo2 { char x; int :0; char y; };
+int foo1test[ sizeof (struct foo1) == 2 ? 1 : -1 ];
+int foo2test[ sizeof (struct foo2) == 5 ? 1 : -1]; ],
+      [], gt_cv_bitfield_type_matters=yes, gt_cv_bitfield_type_matters=no)
+  ])
+  if test $gt_cv_bitfield_type_matters = yes; then
+    AC_DEFINE(HAVE_BITFIELD_TYPE_MATTERS, 1,
+      [Define if the type of bitfields effects alignment.])
+  fi
+])
diff --git a/libobjc/acinclude.m4 b/libobjc/acinclude.m4
index bf78dbe..4193018 100644
--- a/libobjc/acinclude.m4
+++ b/libobjc/acinclude.m4
@@ -12,6 +12,7 @@ m4_include(../config/acx.m4)
 m4_include(../config/no-executables.m4)
 m4_include(../config/enable.m4)
 m4_include(../config/tls.m4)
+m4_include(../config/bitfields.m4)
 
 m4_include(../libtool.m4)
 dnl The lines below arrange for aclocal not to bring an installed
diff --git a/libobjc/config.h.in b/libobjc/config.h.in
index c055e7c..20d1fca 100644
--- a/libobjc/config.h.in
+++ b/libobjc/config.h.in
@@ -1,5 +1,8 @@
 /* config.h.in.  Generated from configure.ac by autoheader.  */
 
+/* Define if the type of bitfields effects alignment. */
+#undef HAVE_BITFIELD_TYPE_MATTERS
+
 /* Define to 1 if the target assembler supports thread-local storage. */
 #undef HAVE_CC_TLS
 
diff --git a/libobjc/configure b/libobjc/configure
index 642eb9c..0547f91 100755
--- a/libobjc/configure
+++ b/libobjc/configure
@@ -11530,6 +11530,44 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_exception_model_name" >&5
 $as_echo "$ac_exception_model_name" >&6; }
 
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking if the type of bitfields matters" >&5
+$as_echo_n "checking if the type of bitfields matters... " >&6; }
+if test "${gt_cv_bitfield_type_matters+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+
+    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+struct foo1 { char x; char :0; char y; };
+struct foo2 { char x; int :0; char y; };
+int foo1test[ sizeof (struct foo1) == 2 ? 1 : -1 ];
+int foo2test[ sizeof (struct foo2) == 5 ? 1 : -1];
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  gt_cv_bitfield_type_matters=yes
+else
+  gt_cv_bitfield_type_matters=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gt_cv_bitfield_type_matters" >&5
+$as_echo "$gt_cv_bitfield_type_matters" >&6; }
+  if test $gt_cv_bitfield_type_matters = yes; then
+
+$as_echo "#define HAVE_BITFIELD_TYPE_MATTERS 1" >>confdefs.h
+
+  fi
+
+
 # ------
 # Output
 # ------
diff --git a/libobjc/configure.ac b/libobjc/configure.ac
index c794a80..2d88519 100644
--- a/libobjc/configure.ac
+++ b/libobjc/configure.ac
@@ -266,6 +266,8 @@ fi
 AC_LANG_POP(C)
 AC_MSG_RESULT($ac_exception_model_name)
 
+gt_BITFIELD_TYPE_MATTERS
+
 # ------
 # Output
 # ------
diff --git a/libobjc/encoding.c b/libobjc/encoding.c
index 20ace46..abb6145 100644
--- a/libobjc/encoding.c
+++ b/libobjc/encoding.c
@@ -29,6 +29,7 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 /* FIXME: This file contains functions that will abort the entire
    program if they fail.  Is that really needed ?  */
 
+#include "config.h"
 #include "objc-private/common.h"
 #include "objc-private/error.h"
 #include "tconfig.h"
@@ -1167,7 +1168,7 @@ objc_layout_structure_next_member (struct objc_struct_layout *layout)
   /* Record must have at least as much alignment as any field.
      Otherwise, the alignment of the field within the record
      is meaningless.  */
-#if !PCC_BITFIELD_TYPE_MATTERS
+#ifndef HAVE_BITFIELD_TYPE_MATTERS
   layout->record_align = MAX (layout->record_align, desired_align);
 #else	/* PCC_BITFIELD_TYPE_MATTERS */
   if (*type == _C_BFLD)
-- 
2.3.0.80.g18d0fec.dirty