Re: [RFC] printing/setting flag register fields

[Tom Tromey <tromey@redhat.com>]

>>>>> "Doug" == Doug Evans <dje@google.com> writes:

Doug> An off-the-cuff example is an option to ptype to print field
Doug> offsets for structs in general.  [I'm assuming such a facility
Doug> doesn't already exist.]  That would probably be more useful than
Doug> always printing the offsets anyway.

I once wrote a simple, C/C++-only patch to add pahole-like output to
ptype.  I appended it.

Also in the archer repository there is a "pahole" command written in
Python.  It does something similar.

I like the idea of an option to ptype.

Tom

diff --git a/gdb/c-typeprint.c b/gdb/c-typeprint.c
index 56d12f9..c38fc31 100644
--- a/gdb/c-typeprint.c
+++ b/gdb/c-typeprint.c
@@ -744,6 +744,9 @@ c_type_print_base (struct type *type, struct ui_file *stream, int show,
 	}
       else if (show > 0 || TYPE_TAG_NAME (type) == NULL)
 	{
+	  int bitpos, field_size;
+	  int is_union = TYPE_CODE (type) == TYPE_CODE_UNION;
+
 	  cp_type_print_derivation_info (stream, type);
 
 	  fprintf_filtered (stream, "{\n");
@@ -830,6 +833,7 @@ c_type_print_base (struct type *type, struct ui_file *stream, int show,
 	  /* If there is a base class for this type,
 	     do not print the field that it occupies.  */
 
+	  bitpos = 0;
 	  len = TYPE_NFIELDS (type);
 	  for (i = TYPE_N_BASECLASSES (type); i < len; i++)
 	    {
@@ -871,6 +875,25 @@ c_type_print_base (struct type *type, struct ui_file *stream, int show,
 		    }
 		}
 
+	      if (!is_union && bitpos != TYPE_FIELD_BITPOS (type, i))
+		{
+		  fprintf_filtered (stream,
+				    "\n /* XXX %d bit hole, try to pack */\n\n",
+				    TYPE_FIELD_BITPOS (type, i) - bitpos);
+		  bitpos = TYPE_FIELD_BITPOS (type, i);
+		}
+	      if (TYPE_FIELD_PACKED (type, i))
+		field_size = TYPE_FIELD_BITSIZE (type, i);
+	      else
+		field_size = 8 * TYPE_LENGTH (TYPE_FIELD_TYPE (type, i)); /* FIXME */
+
+	      if (is_union)
+		print_spaces_filtered (14, stream);
+	      else
+		fprintf_filtered (stream, " /* %3d %3d */",
+				  bitpos / 8, field_size / 8);
+	      bitpos += field_size;
+
 	      print_spaces_filtered (level + 4, stream);
 	      if (TYPE_FIELD_STATIC (type, i))
 		{
@@ -1036,6 +1059,8 @@ c_type_print_base (struct type *type, struct ui_file *stream, int show,
 		}
 	    }
 
+	  if (level)
+	    print_spaces_filtered (14, stream);
 	  fprintfi_filtered (level, stream, "}");
 
 	  if (TYPE_LOCALTYPE_PTR (type) && show >= 0)