[Ada] Fix size increase for packed record with aliased component

Message ID 130773067.boaW8Y2ydQ@polaris
State New
Headers show
Series
  • [Ada] Fix size increase for packed record with aliased component
Related show

Commit Message

Eric Botcazou Sept. 23, 2019, 7:46 a.m.
This fixes a fallout of the reordering of components in record types that was 
enabled some time ago: the size of a packed record with an aliased component 
may be larger than the size that would have been given by a textual layout of 
the record type.

Tested on x86_64-suse-linux, applied on the mainline.


2019-09-23  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc-interface/decl.c (components_to_record): Do not reorder fields
	in packed record types if they contain fixed-size fields that cannot
	be laid out in a packed manner.

-- 
Eric Botcazou

Patch

Index: gcc-interface/decl.c
===================================================================
--- gcc-interface/decl.c	(revision 275988)
+++ gcc-interface/decl.c	(working copy)
@@ -7521,6 +7521,7 @@  components_to_record (Node_Id gnat_compo
   bool all_rep_and_size = all_rep && TYPE_SIZE (gnu_record_type);
   bool variants_have_rep = all_rep;
   bool layout_with_rep = false;
+  bool has_non_packed_fixed_size_field = false;
   bool has_self_field = false;
   bool has_aliased_after_self_field = false;
   Entity_Id gnat_component_decl, gnat_variant_part;
@@ -7577,6 +7578,10 @@  components_to_record (Node_Id gnat_compo
 		  has_self_field = true;
 		else if (has_self_field && DECL_ALIASED_P (gnu_field))
 		  has_aliased_after_self_field = true;
+		else if (!DECL_FIELD_OFFSET (gnu_field)
+			 && !DECL_PACKED (gnu_field)
+			 && !field_has_variable_size (gnu_field))
+		  has_non_packed_fixed_size_field = true;
 	      }
 	  }
 
@@ -7868,8 +7873,9 @@  components_to_record (Node_Id gnat_compo
      self-referential/variable offset or misaligned.  Note, in the latter
      case, that this can only happen in packed record types so the alignment
      is effectively capped to the byte for the whole record.  But we don't
-     do it for non-packed record types if pragma Optimize_Alignment (Space)
-     is specified because this can prevent alignment gaps from being filled.
+     do it for packed record types if not all fixed-size fiels can be packed
+     and for non-packed record types if pragma Optimize_Alignment (Space) is
+     specified, because this can prevent alignment gaps from being filled.
 
      Optionally, if the layout warning is enabled, keep track of the above 4
      different kinds of fields and issue a warning if some of them would be
@@ -7880,8 +7886,9 @@  components_to_record (Node_Id gnat_compo
   const bool do_reorder
     = (Convention (gnat_record_type) == Convention_Ada
        && !No_Reordering (gnat_record_type)
-       && (!Optimize_Alignment_Space (gnat_record_type)
-	   || Is_Packed (gnat_record_type))
+       && !(Is_Packed (gnat_record_type)
+	    ? has_non_packed_fixed_size_field
+	    : Optimize_Alignment_Space (gnat_record_type))
        && !debug__debug_flag_dot_r);
   const bool w_reorder
     = (Convention (gnat_record_type) == Convention_Ada