stor-layout.c (bit_field_mode_iterator::bit_field_mode_iterator): Deal with…

stor-layout.c (bit_field_mode_iterator::bit_field_mode_iterator): Deal with degenerate cases where the bitsize isn't positive.

	* stor-layout.c (bit_field_mode_iterator::bit_field_mode_iterator): Deal
	with degenerate cases where the bitsize isn't positive.  Rework comment.

From-SVN: r194009

gcc/ChangeLog

+2012-11-30  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* stor-layout.c (bit_field_mode_iterator::bit_field_mode_iterator): Deal
+	with degenerate cases where the bitsize isn't positive.  Rework comment.
+
 2012-11-30  David Edelsohn  <dje.gcc@gmail.com>
 
 	* xcoffout.c (xcoff_tls_data_section_name): Define.

gcc/stor-layout.c

@@ -2648,10 +2648,14 @@ bit_field_mode_iterator
 {
   if (!bitregion_end_)
     {
-      /* We can assume that any aligned chunk of UNITS bits that overlaps
-	 the bitfield is mapped and won't trap.  */
-      unsigned HOST_WIDE_INT units = MIN (align, MAX (BIGGEST_ALIGNMENT,
-						      BITS_PER_WORD));
+      /* We can assume that any aligned chunk of ALIGN bits that overlaps
+	 the bitfield is mapped and won't trap, provided that ALIGN isn't
+	 too large.  The cap is the biggest required alignment for data,
+	 or at least the word size.  And force one such chunk at least.  */
+      unsigned HOST_WIDE_INT units
+	= MIN (align, MAX (BIGGEST_ALIGNMENT, BITS_PER_WORD));
+      if (bitsize <= 0)
+	bitsize = 1;
       bitregion_end_ = bitpos + bitsize + units - 1;
       bitregion_end_ -= bitregion_end_ % units + 1;
     }

gcc/testsuite/ChangeLog

+2012-11-30  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gnat.dg/specs/pack9.ads: New test.
+
 2012-11-30  Martin Jambor  <mjambor@suse.cz>
 
 	PR middle-end/52890

gcc/testsuite/gnat.dg/specs/pack9.ads

+-- { dg-do compile }
+
+package Pack9 is
+
+  subtype Zero is Natural range 0 .. 0;
+
+  type Rec (D : Boolean) is record
+    case D is
+       when True => Z : Zero;
+       when False => null;
+    end case;
+  end record;
+  pragma Pack (Rec);
+    
+end Pack9;