Patchwork [c/c++] : Fix for PR c/52991 issue about ignored packed-attribute for ms-structure-layout

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Submitter Kai Tietz
Date Dec. 12, 2012, 7:34 p.m.
Message ID <CAEwic4ak3FwpnXZeyfzGxFC3DrnLAJ-zbJfqVpCynAYfs+Hy2g@mail.gmail.com>
Download mbox | patch
Permalink /patch/205630/
State New
Headers show

Comments

Kai Tietz - Dec. 12, 2012, 7:34 p.m.
Hi,

I added two testcases  to this patch.  So that we might detect
regressions about this issue later more easily.

2012-12-12  Kai Tietz

        PR c/52991
        * stor-layout.c (start_record_layout): Handle
        packed-attribute for ms-structure-layout.
        (update_alignment_for_field): Likewise.
        (place_field): Likewise.

2012-12-12  Kai Tietz

        PR c/52991
	* gcc.dg/attr-ms_struct-packed2.c: New file.
	* gcc.dg/attr-ms_struct-packed3.c: New file.

Ok for apply?

Regards,
Kai

+}

Patch

Index: gcc/gcc/stor-layout.c
===================================================================
--- gcc.orig/gcc/stor-layout.c
+++ gcc/gcc/stor-layout.c
@@ -756,7 +756,10 @@  start_record_layout (tree t)
   /* If the type has a minimum specified alignment (via an attribute
      declaration, for example) use it -- otherwise, start with a
      one-byte alignment.  */
-  rli->record_align = MAX (BITS_PER_UNIT, TYPE_ALIGN (t));
+  if (TYPE_PACKED (t))
+    rli->record_align = BITS_PER_UNIT;
+  else
+    rli->record_align = MAX (BITS_PER_UNIT, TYPE_ALIGN (t));
   rli->unpacked_align = rli->record_align;
   rli->offset_align = MAX (rli->record_align, BIGGEST_ALIGNMENT);

@@ -952,15 +955,20 @@  update_alignment_for_field (record_layou
      meaningless.  */
   if (targetm.ms_bitfield_layout_p (rli->t))
     {
+      if (rli->t && TYPE_PACKED (rli->t)
+          && (is_bitfield || !DECL_PACKED (field)
+              || DECL_SIZE (field) == NULL_TREE
+              || !integer_zerop (DECL_SIZE (field))))
+        desired_align = BITS_PER_UNIT;
       /* Here, the alignment of the underlying type of a bitfield can
 	 affect the alignment of a record; even a zero-sized field
 	 can do this.  The alignment should be to the alignment of
 	 the type, except that for zero-size bitfields this only
 	 applies if there was an immediately prior, nonzero-size
 	 bitfield.  (That's the way it is, experimentally.) */
-      if ((!is_bitfield && !DECL_PACKED (field))
-	  || ((DECL_SIZE (field) == NULL_TREE
-	       || !integer_zerop (DECL_SIZE (field)))
+      else if ((!is_bitfield && !DECL_PACKED (field))
+	       || ((DECL_SIZE (field) == NULL_TREE
+		   || !integer_zerop (DECL_SIZE (field)))
 	      ? !DECL_PACKED (field)
 	      : (rli->prev_field
 		 && DECL_BIT_FIELD_TYPE (rli->prev_field)
@@ -1414,7 +1422,12 @@  place_field (record_layout_info rli, tre
 	    }

 	  /* Now align (conventionally) for the new type.  */
-	  type_align = TYPE_ALIGN (TREE_TYPE (field));
+	  if (!TYPE_PACKED (rli->t))
+	    {
+	      type_align = TYPE_ALIGN (TREE_TYPE (field));
+	      if (DECL_PACKED (field))
+	        type_align = MIN (type_align, BITS_PER_UNIT);
+	    }

 	  if (maximum_field_alignment != 0)
 	    type_align = MIN (type_align, maximum_field_alignment);
Index: gcc/gcc/testsuite/gcc.dg/attr-ms_struct-packed2.c
===================================================================
--- /dev/null
+++ gcc/gcc/testsuite/gcc.dg/attr-ms_struct-packed2.c
@@ -0,0 +1,31 @@ 
+/* Test for MS structure with packed attribute.  */
+/* { dg-do run { target *-*-interix* *-*-mingw* *-*-cygwin*
i?86-*-darwin* i?86-*-linux* x86_64-*-linux* } }
+/* { dg-options "-std=gnu99" } */
+
+extern void abort ();
+
+struct A {
+    short s;
+    struct { int i; } __attribute__((__ms_struct__));
+} __attribute__((__ms_struct__, __packed__));
+
+struct B {
+    short s;
+    struct { int i; } __attribute__((__ms_struct__, __packed__));
+} __attribute__((__ms_struct__, __packed__));
+
+struct C {
+    struct { int i; } __attribute__((__ms_struct__));
+    short s;
+} __attribute__((__ms_struct__, __packed__));
+
+int
+main (void)
+{
+  if (sizeof (struct C) != sizeof (struct B)
+      || sizeof (struct A) != sizeof (struct B)
+      || sizeof (struct B) != 6)
+    abort ();
+
+  return 0;