Re: MI: type prefixes for values

[Vladimir Prus <ghost at cs dot msu dot su>]

Any comments on the patch I've send two weeks ago? Note that I'm not longer
interested in this patch myself, since I no longer use "--stack-list-frames
--all-values" in KDevelop, but I believe the patch affects the MI support
in Emacs that Nick is working on.

- Volodya

>> - print_frame_args, where it is used to deliberately print
>>   only the address of a reference.  I'm not entirely sure why.
>> 
>> - Languages, to implement value_print - not relevant right now.
> 
> It appears that 'common_val_print' has 'deref_ref' parameter which can be
> used to get back the old behaviour. However, then we'll again get no
> output if there's any undereferencable reference.
> 
> I attach a patch that addresses this issue -- now, undereferencable
> references don't throw. For dereferencable references the value is printed
> after ":" as it is now.
> 
> Changelog:
> 
> 2006-04-04 Vladimir Prus <ghost@cs.msu.su>
> 
>     * c-valprint.c (c_val_print): Explicitly check if a reference
>       is dereferencable.
>     * valops.c (value_at_maybe): New function
>     * value.h (value_at_maybe): Export.
>     * mi/mi-cmd-stack.c (list_args_or_locals): Use 'common_val_print',
>      instead of 'print_value_value'. Remove code duplication.
> 
> Patch is attached.
> 
> - Volodya

Index: c-valprint.c
===================================================================
RCS file: /cvs/src/src/gdb/c-valprint.c,v
retrieving revision 1.39
diff -u -p -r1.39 c-valprint.c
--- c-valprint.c	18 Jan 2006 21:24:19 -0000	1.39
+++ c-valprint.c	6 Apr 2006 08:28:55 -0000
@@ -277,13 +277,16 @@ c_val_print (struct type *type, const gd
 	{
 	  if (TYPE_CODE (elttype) != TYPE_CODE_UNDEF)
 	    {
-	      struct value *deref_val =
-	      value_at
-	      (TYPE_TARGET_TYPE (type),
-	       unpack_pointer (lookup_pointer_type (builtin_type_void),
-			       valaddr + embedded_offset));
-	      common_val_print (deref_val, stream, format, deref_ref,
-				recurse, pretty);
+              CORE_ADDR addr = unpack_pointer (
+                  lookup_pointer_type (builtin_type_void),
+                  valaddr + embedded_offset);
+              struct value *deref_val = value_at_maybe(TYPE_TARGET_TYPE(type), 
+                                                       addr);
+              if (deref_val)
+                common_val_print (deref_val, stream, format, deref_ref,
+                                  recurse, pretty);
+              else
+                fputs_filtered("memory not accessible", stream);
 	    }
 	  else
 	    fputs_filtered ("???", stream);
Index: valops.c
===================================================================
RCS file: /cvs/src/src/gdb/valops.c,v
retrieving revision 1.163
diff -u -p -r1.163 valops.c
--- valops.c	17 Dec 2005 22:34:03 -0000	1.163
+++ valops.c	6 Apr 2006 08:28:55 -0000
@@ -472,6 +472,36 @@ value_at (struct type *type, CORE_ADDR a
   return val;
 }
 
+
+/* Same as 'value_at', but returns NULL when memory can't be read
+   instead of throwing.
+*/
+struct value* 
+value_at_maybe (struct type *type, CORE_ADDR addr)
+{
+  struct value *val;
+  int status;
+
+  if (TYPE_CODE (check_typedef (type)) == TYPE_CODE_VOID)
+    error (_("Attempt to dereference a generic pointer."));
+
+
+  val = allocate_value (type);
+  status = target_read_memory (addr, value_contents_all_raw(val), 
+                               TYPE_LENGTH (type));
+  if (status == 0)
+    {      
+      VALUE_LVAL (val) = lval_memory;
+      VALUE_ADDRESS (val) = addr;
+      return val;
+    }
+  else
+    {
+      return 0;  
+    }
+}
+
+
 /* Return a lazy value with type TYPE located at ADDR (cf. value_at).  */
 
 struct value *
Index: value.h
===================================================================
RCS file: /cvs/src/src/gdb/value.h,v
retrieving revision 1.90
diff -u -p -r1.90 value.h
--- value.h	1 Feb 2006 23:14:10 -0000	1.90
+++ value.h	6 Apr 2006 08:28:56 -0000
@@ -277,6 +277,8 @@ extern struct value *value_from_string (
 
 extern struct value *value_at (struct type *type, CORE_ADDR addr);
 extern struct value *value_at_lazy (struct type *type, CORE_ADDR addr);
+extern struct value *value_at_maybe (struct type *type, CORE_ADDR addr);
+
 
 extern struct value *value_from_register (struct type *type, int regnum,
 					  struct frame_info *frame);
Index: mi/mi-cmd-stack.c
===================================================================
RCS file: /cvs/src/src/gdb/mi/mi-cmd-stack.c,v
retrieving revision 1.29
diff -u -p -r1.29 mi-cmd-stack.c
--- mi/mi-cmd-stack.c	23 Dec 2005 18:57:46 -0000	1.29
+++ mi/mi-cmd-stack.c	6 Apr 2006 08:28:56 -0000
@@ -278,6 +278,8 @@ list_args_or_locals (int locals, int val
 	    {
 	      struct cleanup *cleanup_tuple = NULL;
 	      struct symbol *sym2;
+	      struct value *val;
+              int print_it = 0;
 	      if (values != PRINT_NO_VALUES)
 		cleanup_tuple =
 		  make_cleanup_ui_out_tuple_begin_end (uiout, NULL);
@@ -300,17 +302,24 @@ list_args_or_locals (int locals, int val
 		      && TYPE_CODE (type) != TYPE_CODE_STRUCT
 		      && TYPE_CODE (type) != TYPE_CODE_UNION)
 		    {
-		      print_variable_value (sym2, fi, stb->stream);
-		      ui_out_field_stream (uiout, "value", stb);
+                      print_it = 1;
 		    }
 		  do_cleanups (cleanup_tuple);
 		  break;
 		case PRINT_ALL_VALUES:
-		  print_variable_value (sym2, fi, stb->stream);
-		  ui_out_field_stream (uiout, "value", stb);
-		  do_cleanups (cleanup_tuple);
+                    print_it = 1;
 		  break;
 		}
+
+              if (print_it)
+                {
+                  val = read_var_value (sym2, fi);
+		  common_val_print
+		    (val, stb->stream, 0, 1 /*deref refs*/, 2, Val_no_prettyprint);
+		  ui_out_field_stream (uiout, "value", stb);
+		  do_cleanups (cleanup_tuple);                  
+                }
+
 	    }
 	}
       if (BLOCK_FUNCTION (block))