Add ability to report when a variable's value is uninitialized,

based on information provided by the compiler.  Also add new
DWARF OP, DW_OP_GNU_uninit, for this purpose.

gdb/ChangeLog

@@ -1,3 +1,26 @@
+2007-05-18  Caroline Tice  <ctice@apple.com>
+
+	* c-valprint.c (c_value_print):  If the initialized field of the
+	value struct is 0, print out "[uninitialized]" before the value.
+	* dwarf2expr.c (execute_stack_op): Initialize ctx->initialized field; 
+	allow DW_OP_GNU_uninit as legal op following a DW_OP_reg op or a 
+	DW_OP_regx op; add case for DW_OP_GNU_uninit and update
+	ctx->initialized appropriately. Verify no location op follows
+	DW_OP_GNU_uninit.
+	* dwarf2expr.h (struct dwarf_expr_context): New field, initialized.
+	* dwarf2loc.c (dwarf2_evaluate_loc_desc): Add call to 
+	set_value_initialized.
+	* dwarf2read.c (dwarf_stack_op_name): Add case for DW_OP_GNU_uninit.
+	(decode_locdesc): Add case for DW_OP_GNU_uninit.
+	* value.c (struct value):  New field, initialized.
+	(allocate_value): Initialize new field.
+	(set_value_initialized): New function.
+	(value_initialized): New function.
+	* value.h (value_initialized): New extern declaration.
+	(set_value_initialized): Likewise.
+	* include/elf/dwarf2.h: (enum dwarf_location_atom): Add new DW_OP, 
+	DW_OP_GNU_uninit.
+	
 2007-05-18  Caroline Tice  <ctice@apple.com>
 
 	* MAINTAINERS (Write After Approval): Add self.

gdb/c-valprint.c

@@ -556,6 +556,9 @@ c_value_print (struct value *val, struct ui_file *stream, int format,
 	}
     }
 
+  if (!value_initialized (val))
+    fprintf_filtered (stream, " [uninitialized] ");
+
   if (objectprint && (TYPE_CODE (type) == TYPE_CODE_CLASS))
     {
       /* Attempt to determine real type of object */

gdb/dwarf2expr.c

@@ -284,6 +284,7 @@ execute_stack_op (struct dwarf_expr_context *ctx,
 		  gdb_byte *op_ptr, gdb_byte *op_end)
 {
   ctx->in_reg = 0;
+  ctx->initialized = 1;  /* Default is initialized.  */
 
   while (op_ptr < op_end)
     {
@@ -410,7 +411,9 @@ execute_stack_op (struct dwarf_expr_context *ctx,
 	case DW_OP_reg29:
 	case DW_OP_reg30:
 	case DW_OP_reg31:
-	  if (op_ptr != op_end && *op_ptr != DW_OP_piece)
+	  if (op_ptr != op_end 
+	      && *op_ptr != DW_OP_piece
+	      && *op_ptr != DW_OP_GNU_uninit)
 	    error (_("DWARF-2 expression error: DW_OP_reg operations must be "
 		   "used either alone or in conjuction with DW_OP_piece."));
 
@@ -731,6 +734,14 @@ execute_stack_op (struct dwarf_expr_context *ctx,
           }
           goto no_push;
 
+	case DW_OP_GNU_uninit:
+	  if (op_ptr != op_end)
+	    error (_("DWARF-2 expression error: DW_OP_GNU_unint must always "
+		   "be the very last op."));
+
+	  ctx->initialized = 0;
+	  goto no_push;
+
 	default:
 	  error (_("Unhandled dwarf expression opcode 0x%x"), op);
 	}

gdb/dwarf2expr.h

@@ -76,6 +76,10 @@ struct dwarf_expr_context
      will be on the expression stack.  */
   int in_reg;
 
+  /* Initialization status of variable: Non-zero if variable has been
+     initialized; zero otherwise.  */
+  int initialized;
+
   /* An array of pieces.  PIECES points to its first element;
      NUM_PIECES is its length.
 

gdb/dwarf2loc.c

@@ -256,6 +256,8 @@ dwarf2_evaluate_loc_desc (struct symbol *var, struct frame_info *frame,
       VALUE_ADDRESS (retval) = address;
     }
 
+  set_value_initialized (retval, ctx->initialized);
+
   free_dwarf_expr_context (ctx);
 
   return retval;

gdb/dwarf2read.c

@@ -8656,6 +8656,8 @@ dwarf_stack_op_name (unsigned op)
       return "DW_OP_bit_piece";
     case DW_OP_GNU_push_tls_address:
       return "DW_OP_GNU_push_tls_address";
+    case DW_OP_GNU_uninit:
+      return "DW_OP_GNU_uninit";
     /* HP extensions. */ 
     case DW_OP_HP_is_value:
       return "DW_OP_HP_is_value";
@@ -9231,6 +9233,9 @@ decode_locdesc (struct dwarf_block *blk, struct dwarf2_cu *cu)
 	    dwarf2_complex_location_expr_complaint ();
           break;
 
+	case DW_OP_GNU_uninit:
+	  break;
+
 	default:
 	  complaint (&symfile_complaints, _("unsupported stack op: '%s'"),
 		     dwarf_stack_op_name (op));

gdb/value.c

@@ -157,6 +157,9 @@ struct value
      actually exist in the program.  */
   char optimized_out;
 
+  /* If value is a variable, is it initialized or not.  */
+  int initialized;
+
   /* Actual contents of the value.  For use of this value; setting it
      uses the stuff above.  Not valid if lazy is nonzero.  Target
      byte-order.  We force it to be aligned properly for any possible
@@ -232,6 +235,7 @@ allocate_value (struct type *type)
   val->embedded_offset = 0;
   val->pointed_to_offset = 0;
   val->modifiable = 1;
+  val->initialized = 1;  /* Default to initialized.  */
   return val;
 }
 
@@ -1699,6 +1703,22 @@ using_struct_return (struct type *value_type, int gcc_p)
 	  != RETURN_VALUE_REGISTER_CONVENTION);
 }
 
+/* Set the initialized field in a value struct.  */
+
+void
+set_value_initialized (struct value *val, int status)
+{
+  val->initialized = status;
+}
+
+/* Return the initialized field in a value struct.  */
+
+int
+value_initialized (struct value *val)
+{
+  return val->initialized;
+}
+
 void
 _initialize_values (void)
 {

include/elf/dwarf2.h

@@ -540,6 +540,7 @@ enum dwarf_location_atom
     DW_OP_bit_piece = 0x9d,
     /* GNU extensions.  */
     DW_OP_GNU_push_tls_address = 0xe0,
+    DW_OP_GNU_uninit     = 0xf0,
     /* HP extensions.  */
     DW_OP_HP_unknown     = 0xe0, /* Ouch, the same as GNU_push_tls_address.  */
     DW_OP_HP_is_value    = 0xe1,