2010-04-14 Phil Muldoon <pmuldoon@redhat.com>

	PR python/11381

	* python/py-prettyprint.c (pretty_print_one_value): Test for
	Py_None.
	(print_string_repr): Test for Py_None.  Set flags accordingly.
	Return value depending on return type.
	(print_children): Take a value indicating whether data was printed
	before this function was called.  Alter output accordingly.
	(apply_val_pretty_printer): Capture return value from
	print_string_repr and pass to print_children.

2010-04-14  Phil Muldoon  <pmuldoon@redhat.com>

	* gdb.python/py-prettyprint.py (NoStringContainerPrinter): New printer.
	* gdb.python/py-prettyprint.c: Add justchildren struct, typedefs.
	* gdb.python/py-prettyprint.exp: New test for to_string returning None.
	* gdb.python/py-mi.exp: New test for to_string returning None.

2010-04-14  Phil Muldoon  <pmuldoon@redhat.com>

	* gdb.texinfo (Pretty Printing): Document behaviour when to_string
	returns None.

1 files changed, 71 insertions, 46 deletions

diff --git a/gdb/python/py-prettyprint.c b/gdb/python/py-prettyprint.c
index 454aa5a..5c3757c 100644
--- a/gdb/python/py-prettyprint.c
+++ b/gdb/python/py-prettyprint.c
@@ -125,9 +125,12 @@ find_pretty_printer (PyObject *value)
 
 /* Pretty-print a single value, via the printer object PRINTER.
    If the function returns a string, a PyObject containing the string
-   is returned.  Otherwise, if the function returns a value,
-   *OUT_VALUE is set to the value, and NULL is returned.  On error,
-   *OUT_VALUE is set to NULL, and NULL is returned.  */
+   is returned.  If the function returns Py_NONE that means the pretty
+   printer returned the Python None as a value.  Otherwise, if the
+   function returns a value,  *OUT_VALUE is set to the value, and NULL
+   is returned.  On error, *OUT_VALUE is set to NULL, and NULL is
+   returned.  */
+
 static PyObject *
 pretty_print_one_value (PyObject *printer, struct value **out_value)
 {
@@ -140,7 +143,8 @@ pretty_print_one_value (PyObject *printer, struct value **out_value)
       result = PyObject_CallMethodObjArgs (printer, gdbpy_to_string_cst, NULL);
       if (result)
 	{
-	  if (! gdbpy_is_string (result) && ! gdbpy_is_lazy_string (result))
+	  if (! gdbpy_is_string (result) && ! gdbpy_is_lazy_string (result)  
+	      && result != Py_None)
 	    {
 	      *out_value = convert_value_from_python (result);
 	      if (PyErr_Occurred ())
@@ -179,8 +183,11 @@ gdbpy_get_display_hint (PyObject *printer)
 }
 
 /* Helper for apply_val_pretty_printer which calls to_string and
-   formats the result.  */
-static void
+   formats the result.  If the value returnd is Py_None, nothing is
+   printed and the function returns a 1; in all other cases data is
+   printed as given by the pretty printer and the function returns 0.
+*/
+static int
 print_string_repr (PyObject *printer, const char *hint,
 		   struct ui_file *stream, int recurse,
 		   const struct value_print_options *options,
@@ -189,52 +196,58 @@ print_string_repr (PyObject *printer, const char *hint,
 {
   struct value *replacement = NULL;
   PyObject *py_str = NULL;
+  int is_py_none = 0;
 
   py_str = pretty_print_one_value (printer, &replacement);
   if (py_str)
     {
-      gdb_byte *output = NULL;
-      long length;
-      struct type *type;
-      char *encoding = NULL;
-      PyObject *string = NULL;
-      int is_lazy;
-      
-      is_lazy = gdbpy_is_lazy_string (py_str);
-      if (is_lazy)
-	output = gdbpy_extract_lazy_string (py_str, &type, &length, &encoding);
+      if (py_str == Py_None)
+	is_py_none = 1;
       else
 	{
-	  string = python_string_to_target_python_string (py_str);
-	  if (string)
+	  gdb_byte *output = NULL;
+	  long length;
+	  struct type *type;
+	  char *encoding = NULL;
+	  PyObject *string = NULL;
+	  int is_lazy;
+
+	  is_lazy = gdbpy_is_lazy_string (py_str);
+	  if (is_lazy)
+	    output = gdbpy_extract_lazy_string (py_str, &type, &length, &encoding);
+	  else
 	    {
-	      output = PyString_AsString (string);
-	      length = PyString_Size (string);
-	      type = builtin_type (gdbarch)->builtin_char;
+	      string = python_string_to_target_python_string (py_str);
+	      if (string)
+		{
+		  output = PyString_AsString (string);
+		  length = PyString_Size (string);
+		  type = builtin_type (gdbarch)->builtin_char;
+		}
+	      else
+		gdbpy_print_stack ();
+	      
+	    }
+	
+	  if (output)
+	    {
+	      if (is_lazy || (hint && !strcmp (hint, "string")))
+		LA_PRINT_STRING (stream, type, output, length, encoding,
+				 0, options);
+	      else
+		fputs_filtered (output, stream);
 	    }
 	  else
 	    gdbpy_print_stack ();
 	  
-	}
-      
-      if (output)
-	{
-	  if (is_lazy || (hint && !strcmp (hint, "string")))
-	    LA_PRINT_STRING (stream, type, output, length, encoding,
-			     0, options);
+	  if (string)
+	    Py_DECREF (string);
 	  else
-	    fputs_filtered (output, stream);
-	}
-      else
-	gdbpy_print_stack ();
+	    xfree (output);
       
-      if (string)
-	Py_DECREF (string);
-      else
-	xfree (output);
-      
-      xfree (encoding);
-      Py_DECREF (py_str);
+	  xfree (encoding);
+	  Py_DECREF (py_str);
+	}
     }
   else if (replacement)
     {
@@ -245,6 +258,8 @@ print_string_repr (PyObject *printer, const char *hint,
     }
   else
     gdbpy_print_stack ();
+
+  return is_py_none;
 }
 
 static void
@@ -323,12 +338,14 @@ push_dummy_python_frame ()
 }
 
 /* Helper for apply_val_pretty_printer that formats children of the
-   printer, if any exist.  */
+   printer, if any exist.  If is_py_none is true, then nothing has
+   been printed by to_string, and format output accordingly. */
 static void
 print_children (PyObject *printer, const char *hint,
 		struct ui_file *stream, int recurse,
 		const struct value_print_options *options,
-		const struct language_defn *language)
+		const struct language_defn *language,
+		int is_py_none)
 {
   int is_map, is_array, done_flag, pretty;
   unsigned int i;
@@ -408,7 +425,13 @@ print_children (PyObject *printer, const char *hint,
 	 2. Arrays.  Always print a ",".
 	 3. Other.  Always print a ",".  */
       if (i == 0)
-	fputs_filtered (" = {", stream);
+	{
+         if (is_py_none)
+           fputs_filtered ("{", stream);
+         else
+           fputs_filtered (" = {", stream);
+       }
+
       else if (! is_map || i % 2 == 0)
 	fputs_filtered (pretty ? "," : ", ", stream);
 
@@ -532,7 +555,7 @@ apply_val_pretty_printer (struct type *type, const gdb_byte *valaddr,
   char *hint = NULL;
   struct cleanup *cleanups;
   int result = 0;
-
+  int is_py_none = 0;
   cleanups = ensure_python_env (gdbarch, language);
 
   /* Instantiate the printer.  */
@@ -557,9 +580,11 @@ apply_val_pretty_printer (struct type *type, const gdb_byte *valaddr,
   make_cleanup (free_current_contents, &hint);
 
   /* Print the section */
-  print_string_repr (printer, hint, stream, recurse, options, language,
-		     gdbarch);
-  print_children (printer, hint, stream, recurse, options, language);
+  is_py_none = print_string_repr (printer, hint, stream, recurse,
+				  options, language, gdbarch);
+  print_children (printer, hint, stream, recurse, options, language,
+		  is_py_none);
+
   result = 1;