Re: [PATCH] Fix usage of to_string() for pretty-printers with children

[Peter Linss <peter@elemental.software>]

> On May 25, 2017, at 7:59 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Peter Linss <peter@elemental.software>
>> Date: Wed, 24 May 2017 19:33:41 -0700
>> 
>> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
>> index 9fb70f6d2a..05e5b868ed 100644
>> --- a/gdb/doc/gdb.texinfo
>> +++ b/gdb/doc/gdb.texinfo
>> @@ -29444,8 +29444,9 @@ reliable for a dynamic varobj.  Instead, you must examine the
>> 
>> @item value
>> The varobj's scalar value.  For a varobj whose type is some sort of
>> -aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
>> -will not be interesting.
>> +aggregate (e.g., a @code{struct}) this value will not be interesting.
>                                    ^
> Please add back the comma removed here.
> 
> The documentation part is approved with this gotcha fixed.
> 
> Thanks.


Revised patch with comma restored (not sure if you want a new email thread for small patch revisions like this):

—

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 9fb70f6d2a..ff2992e433 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -29444,8 +29444,9 @@ reliable for a dynamic varobj.  Instead, you must examine the
 
 @item value
 The varobj's scalar value.  For a varobj whose type is some sort of
-aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
-will not be interesting.
+aggregate (e.g., a @code{struct}), this value will not be interesting.
+For a dynamic varobj, this value comes from the Python pretty-printer
+object's @code{to_string} method, if present.  @xref{Pretty Printing API}.
 
 @item type
 The varobj's type.  This is a string representation of the type, as
diff --git a/gdb/varobj.c b/gdb/varobj.c
index 7bd549d45c..925c6318a8 100644
--- a/gdb/varobj.c
+++ b/gdb/varobj.c
@@ -686,21 +686,6 @@ install_dynamic_child (struct varobj *var,
     }
 }
 
-#if HAVE_PYTHON
-
-static int
-dynamic_varobj_has_child_method (const struct varobj *var)
-{
-  PyObject *printer = var->dynamic->pretty_printer;
-
-  if (!gdb_python_initialized)
-    return 0;
-
-  gdbpy_enter_varobj enter_py (var);
-  return PyObject_HasAttr (printer, gdbpy_children_cst);
-}
-#endif
-
 /* A factory for creating dynamic varobj's iterators.  Returns an
    iterator object suitable for iterating over VAR's children.  */
 
@@ -2420,11 +2405,6 @@ varobj_value_get_print_value (struct value *value,
 
       if (value_formatter)
 	{
-	  /* First check to see if we have any children at all.  If so,
-	     we simply return {...}.  */
-	  if (dynamic_varobj_has_child_method (var))
-	    return "{...}";
-
 	  if (PyObject_HasAttr (value_formatter, gdbpy_to_string_cst))
 	    {
 	      struct value *replacement;
@@ -2486,6 +2466,13 @@ varobj_value_get_print_value (struct value *value,
 	      if (replacement)
 		value = replacement;
 	    }
+	  else
+	    {
+	      /* If we don't have to_string but we have children,
+		 we simply return {...}.  */
+	      if (PyObject_HasAttr (value_formatter, gdbpy_children_cst))
+		return "{...}";
+	    }
 	}
     }
 #endif