Make "bt N" print correct number of frames when using a frame filter
[deliverable/binutils-gdb.git] / gdb / python / py-framefilter.c
index 4c7757cbb930b29bec7f8288076d01018fd54106..3a3fb97c6c26da963f269f8b6bc1f5c4cb28105b 100644 (file)
@@ -1,6 +1,6 @@
 /* Python frame filters
 
-   Copyright (C) 2013-2016 Free Software Foundation, Inc.
+   Copyright (C) 2013-2018 Free Software Foundation, Inc.
 
    This file is part of GDB.
 
@@ -30,6 +30,8 @@
 #include "demangle.h"
 #include "mi/mi-cmds.h"
 #include "python-internal.h"
+#include "py-ref.h"
+#include "common/gdb_optional.h"
 
 enum mi_print_types
 {
@@ -52,20 +54,20 @@ enum mi_print_types
    appropriate Python exception set, and EXT_LANG_BT_OK on success.  */
 
 static enum ext_lang_bt_status
-extract_sym (PyObject *obj, char **name, struct symbol **sym,
-            struct block **sym_block, const struct language_defn **language)
+extract_sym (PyObject *obj, gdb::unique_xmalloc_ptr<char> *name,
+            struct symbol **sym, struct block **sym_block,
+            const struct language_defn **language)
 {
-  PyObject *result = PyObject_CallMethod (obj, "symbol", NULL);
+  gdbpy_ref<> result (PyObject_CallMethod (obj, "symbol", NULL));
 
   if (result == NULL)
     return EXT_LANG_BT_ERROR;
 
   /* For 'symbol' callback, the function can return a symbol or a
      string.  */
-  if (gdbpy_is_string (result))
+  if (gdbpy_is_string (result.get ()))
     {
-      *name = python_string_to_host_string (result);
-      Py_DECREF (result);
+      *name = python_string_to_host_string (result.get ());
 
       if (*name == NULL)
        return EXT_LANG_BT_ERROR;
@@ -82,15 +84,13 @@ extract_sym (PyObject *obj, char **name, struct symbol **sym,
     {
       /* This type checks 'result' during the conversion so we
         just call it unconditionally and check the return.  */
-      *sym = symbol_object_to_symbol (result);
+      *sym = symbol_object_to_symbol (result.get ());
       /* TODO: currently, we have no way to recover the block in which SYMBOL
         was found, so we have no block to return.  Trying to evaluate SYMBOL
         will yield an incorrect value when it's located in a FRAME and
         evaluated from another frame (as permitted in nested functions).  */
       *sym_block = NULL;
 
-      Py_DECREF (result);
-
       if (*sym == NULL)
        {
          PyErr_SetString (PyExc_RuntimeError,
@@ -101,7 +101,7 @@ extract_sym (PyObject *obj, char **name, struct symbol **sym,
 
       /* Duplicate the symbol name, so the caller has consistency
         in garbage collection.  */
-      *name = xstrdup (SYMBOL_PRINT_NAME (*sym));
+      name->reset (xstrdup (SYMBOL_PRINT_NAME (*sym)));
 
       /* If a symbol is specified attempt to determine the language
         from the symbol.  If mode is not "auto", then the language
@@ -129,7 +129,7 @@ extract_value (PyObject *obj, struct value **value)
 {
   if (PyObject_HasAttrString (obj, "value"))
     {
-      PyObject *vresult = PyObject_CallMethod (obj, "value", NULL);
+      gdbpy_ref<> vresult (PyObject_CallMethod (obj, "value", NULL));
 
       if (vresult == NULL)
        return EXT_LANG_BT_ERROR;
@@ -139,14 +139,12 @@ extract_value (PyObject *obj, struct value **value)
         value.  */
       if (vresult == Py_None)
        {
-         Py_DECREF (vresult);
          *value = NULL;
          return EXT_LANG_BT_OK;
        }
       else
        {
-         *value = convert_value_from_python (vresult);
-         Py_DECREF (vresult);
+         *value = convert_value_from_python (vresult.get ());
 
          if (*value == NULL)
            return EXT_LANG_BT_ERROR;
@@ -211,15 +209,11 @@ py_print_type (struct ui_out *out, struct value *val)
 
   TRY
     {
-      struct ui_file *stb;
-      struct cleanup *cleanup;
-
-      stb = mem_fileopen ();
-      cleanup = make_cleanup_ui_file_delete (stb);
       check_typedef (value_type (val));
-      type_print (value_type (val), "", stb, -1);
-      ui_out_field_stream (out, "type", stb);
-      do_cleanups (cleanup);
+
+      string_file stb;
+      type_print (value_type (val), "", &stb, -1);
+      out->field_stream ("type", stb);
     }
   CATCH (except, RETURN_MASK_ALL)
     {
@@ -283,14 +277,10 @@ py_print_value (struct ui_out *out, struct value *val,
     {
       TRY
        {
-         struct ui_file *stb;
-         struct cleanup *cleanup;
-
-         stb = mem_fileopen ();
-         cleanup = make_cleanup_ui_file_delete (stb);
-         common_val_print (val, stb, indent, opts, language);
-         ui_out_field_stream (out, "value", stb);
-         do_cleanups (cleanup);
+         string_file stb;
+
+         common_val_print (val, &stb, indent, opts, language);
+         out->field_stream ("value", stb);
        }
       CATCH (except, RETURN_MASK_ALL)
        {
@@ -311,24 +301,21 @@ py_print_value (struct ui_out *out, struct value *val,
    This function can return an iterator, or NULL.  */
 
 static PyObject *
-get_py_iter_from_func (PyObject *filter, char *func)
+get_py_iter_from_func (PyObject *filter, const char *func)
 {
   if (PyObject_HasAttrString (filter, func))
     {
-      PyObject *result = PyObject_CallMethod (filter, func, NULL);
+      gdbpy_ref<> result (PyObject_CallMethod (filter, func, NULL));
 
       if (result != NULL)
        {
          if (result == Py_None)
            {
-             return result;
+             return result.release ();
            }
          else
            {
-             PyObject *iterator = PyObject_GetIter (result);
-
-             Py_DECREF (result);
-             return iterator;
+             return PyObject_GetIter (result.get ());
            }
        }
     }
@@ -379,7 +366,7 @@ py_print_single_arg (struct ui_out *out,
 
   TRY
     {
-      struct cleanup *cleanups = make_cleanup (null_cleanup, NULL);
+      gdb::optional<ui_out_emit_tuple> maybe_tuple;
 
       /*  MI has varying rules for tuples, but generally if there is only
       one element in each item in the list, do not start a tuple.  The
@@ -387,10 +374,10 @@ py_print_single_arg (struct ui_out *out,
       if the value is a frame argument.  This is denoted in this
       function with PRINT_ARGS_FIELD which is flag from the caller to
       emit the ARGS field.  */
-      if (ui_out_is_mi_like_p (out))
+      if (out->is_mi_like_p ())
        {
          if (print_args_field || args_type != NO_VALUES)
-           make_cleanup_ui_out_tuple_begin_end (out, NULL);
+           maybe_tuple.emplace (out, nullptr);
        }
 
       annotate_arg_begin ();
@@ -399,39 +386,35 @@ py_print_single_arg (struct ui_out *out,
         entry value options.  */
       if (fa != NULL)
        {
-         struct ui_file *stb;
+         string_file stb;
 
-         stb = mem_fileopen ();
-         make_cleanup_ui_file_delete (stb);
-         fprintf_symbol_filtered (stb, SYMBOL_PRINT_NAME (fa->sym),
+         fprintf_symbol_filtered (&stb, SYMBOL_PRINT_NAME (fa->sym),
                                   SYMBOL_LANGUAGE (fa->sym),
                                   DMGL_PARAMS | DMGL_ANSI);
          if (fa->entry_kind == print_entry_values_compact)
            {
-             fputs_filtered ("=", stb);
+             stb.puts ("=");
 
-             fprintf_symbol_filtered (stb, SYMBOL_PRINT_NAME (fa->sym),
+             fprintf_symbol_filtered (&stb, SYMBOL_PRINT_NAME (fa->sym),
                                       SYMBOL_LANGUAGE (fa->sym),
                                       DMGL_PARAMS | DMGL_ANSI);
            }
          if (fa->entry_kind == print_entry_values_only
              || fa->entry_kind == print_entry_values_compact)
-           {
-             fputs_filtered ("@entry", stb);
-           }
-         ui_out_field_stream (out, "name", stb);
+           stb.puts ("@entry");
+         out->field_stream ("name", stb);
        }
       else
        /* Otherwise, just output the name.  */
-       ui_out_field_string (out, "name", sym_name);
+       out->field_string ("name", sym_name);
 
       annotate_arg_name_end ();
 
-      if (! ui_out_is_mi_like_p (out))
-       ui_out_text (out, "=");
+      if (! out->is_mi_like_p ())
+       out->text ("=");
 
       if (print_args_field)
-       ui_out_field_int (out, "arg", 1);
+       out->field_int ("arg", 1);
 
       /* For MI print the type, but only for simple values.  This seems
         weird, but this is how MI choose to format the various output
@@ -439,10 +422,7 @@ py_print_single_arg (struct ui_out *out,
       if (args_type == MI_PRINT_SIMPLE_VALUES && val != NULL)
        {
          if (py_print_type (out, val) == EXT_LANG_BT_ERROR)
-           {
-             retval = EXT_LANG_BT_ERROR;
-             do_cleanups (cleanups);
-           }
+           retval = EXT_LANG_BT_ERROR;
        }
 
       if (retval != EXT_LANG_BT_ERROR)
@@ -452,8 +432,8 @@ py_print_single_arg (struct ui_out *out,
 
          /* If the output is to the CLI, and the user option "set print
             frame-arguments" is set to none, just output "...".  */
-         if (! ui_out_is_mi_like_p (out) && args_type == NO_VALUES)
-           ui_out_field_string (out, "value", "...");
+         if (! out->is_mi_like_p () && args_type == NO_VALUES)
+           out->field_string ("value", "...");
          else
            {
              /* Otherwise, print the value for both MI and the CLI, except
@@ -463,7 +443,7 @@ py_print_single_arg (struct ui_out *out,
                  if (val == NULL)
                    {
                      gdb_assert (fa != NULL && fa->error != NULL);
-                     ui_out_field_fmt (out, "value",
+                     out->field_fmt ("value",
                                        _("<error reading variable: %s>"),
                                        fa->error);
                    }
@@ -472,8 +452,6 @@ py_print_single_arg (struct ui_out *out,
                    retval = EXT_LANG_BT_ERROR;
                }
            }
-
-         do_cleanups (cleanups);
        }
     }
   CATCH (except, RETURN_MASK_ERROR)
@@ -503,7 +481,6 @@ enumerate_args (PyObject *iter,
                int print_args_field,
                struct frame_info *frame)
 {
-  PyObject *item;
   struct value_print_options opts;
 
   get_user_print_options (&opts);
@@ -523,7 +500,7 @@ enumerate_args (PyObject *iter,
   CATCH (except, RETURN_MASK_ALL)
     {
       gdbpy_convert_exception (except);
-      goto error;
+      return EXT_LANG_BT_ERROR;
     }
   END_CATCH
 
@@ -531,43 +508,31 @@ enumerate_args (PyObject *iter,
       commas in the argument output is correct.  At the end of the
       loop block collect another item from the iterator, and, if it is
       not null emit a comma.  */
-  item = PyIter_Next (iter);
+  gdbpy_ref<> item (PyIter_Next (iter));
   if (item == NULL && PyErr_Occurred ())
-    goto error;
+    return EXT_LANG_BT_ERROR;
 
-  while (item)
+  while (item != NULL)
     {
       const struct language_defn *language;
-      char *sym_name;
+      gdb::unique_xmalloc_ptr<char> sym_name;
       struct symbol *sym;
       struct block *sym_block;
       struct value *val;
       enum ext_lang_bt_status success = EXT_LANG_BT_ERROR;
 
-      success = extract_sym (item, &sym_name, &sym, &sym_block, &language);
+      success = extract_sym (item.get (), &sym_name, &sym, &sym_block,
+                            &language);
       if (success == EXT_LANG_BT_ERROR)
-       {
-         Py_DECREF (item);
-         goto error;
-       }
+       return EXT_LANG_BT_ERROR;
 
-      success = extract_value (item, &val);
+      success = extract_value (item.get (), &val);
       if (success == EXT_LANG_BT_ERROR)
-       {
-         xfree (sym_name);
-         Py_DECREF (item);
-         goto error;
-       }
-
-      Py_DECREF (item);
-      item = NULL;
+       return EXT_LANG_BT_ERROR;
 
-      if (sym && ui_out_is_mi_like_p (out)
+      if (sym && out->is_mi_like_p ()
          && ! mi_should_print (sym, MI_PRINT_ARGS))
-       {
-         xfree (sym_name);
-         continue;
-       }
+       continue;
 
       /* If the object did not provide a value, read it using
         read_frame_args and account for entry values, if any.  */
@@ -581,8 +546,7 @@ enumerate_args (PyObject *iter,
            {
              PyErr_SetString (PyExc_RuntimeError,
                               _("No symbol or value provided."));
-             xfree (sym_name);
-             goto error;
+             return EXT_LANG_BT_ERROR;
            }
 
          TRY
@@ -591,9 +555,8 @@ enumerate_args (PyObject *iter,
            }
          CATCH (except, RETURN_MASK_ALL)
            {
-             xfree (sym_name);
              gdbpy_convert_exception (except);
-             goto error;
+             return EXT_LANG_BT_ERROR;
            }
          END_CATCH
 
@@ -611,8 +574,7 @@ enumerate_args (PyObject *iter,
                {
                  xfree (arg.error);
                  xfree (entryarg.error);
-                 xfree (sym_name);
-                 goto error;
+                 return EXT_LANG_BT_ERROR;
                }
            }
 
@@ -622,16 +584,15 @@ enumerate_args (PyObject *iter,
                {
                  TRY
                    {
-                     ui_out_text (out, ", ");
-                     ui_out_wrap_hint (out, "    ");
+                     out->text (", ");
+                     out->wrap_hint ("    ");
                    }
                  CATCH (except, RETURN_MASK_ALL)
                    {
                      xfree (arg.error);
                      xfree (entryarg.error);
-                     xfree (sym_name);
                      gdbpy_convert_exception (except);
-                     goto error;
+                     return EXT_LANG_BT_ERROR;
                    }
                  END_CATCH
                }
@@ -640,10 +601,9 @@ enumerate_args (PyObject *iter,
                                       args_type, print_args_field, NULL)
                  == EXT_LANG_BT_ERROR)
                {
-                     xfree (arg.error);
-                     xfree (entryarg.error);
-                     xfree (sym_name);
-                     goto error;
+                 xfree (arg.error);
+                 xfree (entryarg.error);
+                 return EXT_LANG_BT_ERROR;
                }
            }
 
@@ -655,38 +615,32 @@ enumerate_args (PyObject *iter,
          /* If the object has provided a value, we just print that.  */
          if (val != NULL)
            {
-             if (py_print_single_arg (out, sym_name, NULL, val, &opts,
+             if (py_print_single_arg (out, sym_name.get (), NULL, val, &opts,
                                       args_type, print_args_field,
                                       language) == EXT_LANG_BT_ERROR)
-               {
-                 xfree (sym_name);
-                 goto error;
-               }
+               return EXT_LANG_BT_ERROR;
            }
        }
 
-      xfree (sym_name);
-
       /* Collect the next item from the iterator.  If
         this is the last item, do not print the
         comma.  */
-      item = PyIter_Next (iter);
+      item.reset (PyIter_Next (iter));
       if (item != NULL)
        {
          TRY
            {
-             ui_out_text (out, ", ");
+             out->text (", ");
            }
          CATCH (except, RETURN_MASK_ALL)
            {
-             Py_DECREF (item);
              gdbpy_convert_exception (except);
-             goto error;
+             return EXT_LANG_BT_ERROR;
            }
          END_CATCH
        }
       else if (PyErr_Occurred ())
-       goto error;
+       return EXT_LANG_BT_ERROR;
 
       TRY
        {
@@ -694,17 +648,13 @@ enumerate_args (PyObject *iter,
        }
       CATCH (except, RETURN_MASK_ALL)
        {
-         Py_DECREF (item);
          gdbpy_convert_exception (except);
-         goto error;
+         return EXT_LANG_BT_ERROR;
        }
       END_CATCH
     }
 
   return EXT_LANG_BT_OK;
-
- error:
-  return EXT_LANG_BT_ERROR;
 }
 
 
@@ -727,47 +677,38 @@ enumerate_locals (PyObject *iter,
                  int print_args_field,
                  struct frame_info *frame)
 {
-  PyObject *item;
   struct value_print_options opts;
 
   get_user_print_options (&opts);
   opts.deref_ref = 1;
 
-  while ((item = PyIter_Next (iter)))
+  while (true)
     {
       const struct language_defn *language;
-      char *sym_name;
+      gdb::unique_xmalloc_ptr<char> sym_name;
       struct value *val;
       enum ext_lang_bt_status success = EXT_LANG_BT_ERROR;
       struct symbol *sym;
       struct block *sym_block;
       int local_indent = 8 + (8 * indent);
-      struct cleanup *locals_cleanups;
+      gdb::optional<ui_out_emit_tuple> tuple;
 
-      locals_cleanups = make_cleanup_py_decref (item);
+      gdbpy_ref<> item (PyIter_Next (iter));
+      if (item == NULL)
+       break;
 
-      success = extract_sym (item, &sym_name, &sym, &sym_block, &language);
+      success = extract_sym (item.get (), &sym_name, &sym, &sym_block,
+                            &language);
       if (success == EXT_LANG_BT_ERROR)
-       {
-         do_cleanups (locals_cleanups);
-         goto error;
-       }
-
-      make_cleanup (xfree, sym_name);
+       return EXT_LANG_BT_ERROR;
 
-      success = extract_value (item, &val);
+      success = extract_value (item.get (), &val);
       if (success == EXT_LANG_BT_ERROR)
-       {
-         do_cleanups (locals_cleanups);
-         goto error;
-       }
+       return EXT_LANG_BT_ERROR;
 
-      if (sym != NULL && ui_out_is_mi_like_p (out)
+      if (sym != NULL && out->is_mi_like_p ()
          && ! mi_should_print (sym, MI_PRINT_LOCALS))
-       {
-         do_cleanups (locals_cleanups);
-         continue;
-       }
+       continue;
 
       /* If the object did not provide a value, read it.  */
       if (val == NULL)
@@ -779,8 +720,7 @@ enumerate_locals (PyObject *iter,
          CATCH (except, RETURN_MASK_ERROR)
            {
              gdbpy_convert_exception (except);
-             do_cleanups (locals_cleanups);
-             goto error;
+             return EXT_LANG_BT_ERROR;
            }
          END_CATCH
        }
@@ -788,53 +728,46 @@ enumerate_locals (PyObject *iter,
       /* With PRINT_NO_VALUES, MI does not emit a tuple normally as
         each output contains only one field.  The exception is
         -stack-list-variables, which always provides a tuple.  */
-      if (ui_out_is_mi_like_p (out))
+      if (out->is_mi_like_p ())
        {
          if (print_args_field || args_type != NO_VALUES)
-           make_cleanup_ui_out_tuple_begin_end (out, NULL);
+           tuple.emplace (out, nullptr);
        }
       TRY
        {
-         if (! ui_out_is_mi_like_p (out))
+         if (! out->is_mi_like_p ())
            {
              /* If the output is not MI we indent locals.  */
-             ui_out_spaces (out, local_indent);
+             out->spaces (local_indent);
            }
 
-         ui_out_field_string (out, "name", sym_name);
+         out->field_string ("name", sym_name.get ());
 
-         if (! ui_out_is_mi_like_p (out))
-           ui_out_text (out, " = ");
+         if (! out->is_mi_like_p ())
+           out->text (" = ");
        }
       CATCH (except, RETURN_MASK_ERROR)
        {
          gdbpy_convert_exception (except);
-         do_cleanups (locals_cleanups);
-         goto error;
+         return EXT_LANG_BT_ERROR;
        }
       END_CATCH
 
       if (args_type == MI_PRINT_SIMPLE_VALUES)
        {
          if (py_print_type (out, val) == EXT_LANG_BT_ERROR)
-           {
-             do_cleanups (locals_cleanups);
-             goto error;
-           }
+           return EXT_LANG_BT_ERROR;
        }
 
       /* CLI always prints values for locals.  MI uses the
         simple/no/all system.  */
-      if (! ui_out_is_mi_like_p (out))
+      if (! out->is_mi_like_p ())
        {
          int val_indent = (indent + 1) * 4;
 
          if (py_print_value (out, val, &opts, val_indent, args_type,
                              language) == EXT_LANG_BT_ERROR)
-           {
-             do_cleanups (locals_cleanups);
-             goto error;
-           }
+           return EXT_LANG_BT_ERROR;
        }
       else
        {
@@ -842,33 +775,25 @@ enumerate_locals (PyObject *iter,
            {
              if (py_print_value (out, val, &opts, 0, args_type,
                                  language) == EXT_LANG_BT_ERROR)
-               {
-                 do_cleanups (locals_cleanups);
-                 goto error;
-               }
+               return EXT_LANG_BT_ERROR;
            }
        }
 
-      do_cleanups (locals_cleanups);
-
       TRY
        {
-         ui_out_text (out, "\n");
+         out->text ("\n");
        }
       CATCH (except, RETURN_MASK_ERROR)
        {
          gdbpy_convert_exception (except);
-         goto error;
+         return EXT_LANG_BT_ERROR;
        }
       END_CATCH
     }
 
-  if (item == NULL && PyErr_Occurred ())
-    goto error;
-
-  return EXT_LANG_BT_OK;
+  if (!PyErr_Occurred ())
+    return EXT_LANG_BT_OK;
 
- error:
   return EXT_LANG_BT_ERROR;
 }
 
@@ -881,38 +806,27 @@ py_mi_print_variables (PyObject *filter, struct ui_out *out,
                       enum ext_lang_frame_args args_type,
                       struct frame_info *frame)
 {
-  struct cleanup *old_chain;
-  PyObject *args_iter;
-  PyObject *locals_iter;
-
-  args_iter = get_py_iter_from_func (filter, "frame_args");
-  old_chain = make_cleanup_py_xdecref (args_iter);
+  gdbpy_ref<> args_iter (get_py_iter_from_func (filter, "frame_args"));
   if (args_iter == NULL)
-    goto error;
+    return EXT_LANG_BT_ERROR;
 
-  locals_iter = get_py_iter_from_func (filter, "frame_locals");
+  gdbpy_ref<> locals_iter (get_py_iter_from_func (filter, "frame_locals"));
   if (locals_iter == NULL)
-    goto error;
+    return EXT_LANG_BT_ERROR;
 
-  make_cleanup_py_decref (locals_iter);
-  make_cleanup_ui_out_list_begin_end (out, "variables");
+  ui_out_emit_list list_emitter (out, "variables");
 
-  if (args_iter != Py_None)
-    if (enumerate_args (args_iter, out, args_type, 1, frame)
-       == EXT_LANG_BT_ERROR)
-      goto error;
+  if (args_iter != Py_None
+      && (enumerate_args (args_iter.get (), out, args_type, 1, frame)
+         == EXT_LANG_BT_ERROR))
+    return EXT_LANG_BT_ERROR;
 
-  if (locals_iter != Py_None)
-    if (enumerate_locals (locals_iter, out, 1, args_type, 1, frame)
-       == EXT_LANG_BT_ERROR)
-      goto error;
+  if (locals_iter != Py_None
+      && (enumerate_locals (locals_iter.get (), out, 1, args_type, 1, frame)
+         == EXT_LANG_BT_ERROR))
+    return EXT_LANG_BT_ERROR;
 
-  do_cleanups (old_chain);
   return EXT_LANG_BT_OK;
-
- error:
-  do_cleanups (old_chain);
-  return EXT_LANG_BT_ERROR;
 }
 
 /* Helper function for printing locals.  This function largely just
@@ -926,26 +840,18 @@ py_print_locals (PyObject *filter,
                 int indent,
                 struct frame_info *frame)
 {
-  PyObject *locals_iter = get_py_iter_from_func (filter,
-                                                "frame_locals");
-  struct cleanup *old_chain = make_cleanup_py_xdecref (locals_iter);
-
+  gdbpy_ref<> locals_iter (get_py_iter_from_func (filter, "frame_locals"));
   if (locals_iter == NULL)
-    goto locals_error;
+    return EXT_LANG_BT_ERROR;
 
-  make_cleanup_ui_out_list_begin_end (out, "locals");
+  ui_out_emit_list list_emitter (out, "locals");
 
-  if (locals_iter != Py_None)
-    if (enumerate_locals (locals_iter, out, indent, args_type,
-                         0, frame) == EXT_LANG_BT_ERROR)
-      goto locals_error;
+  if (locals_iter != Py_None
+      && (enumerate_locals (locals_iter.get (), out, indent, args_type,
+                           0, frame) == EXT_LANG_BT_ERROR))
+    return EXT_LANG_BT_ERROR;
 
-  do_cleanups (old_chain);
   return EXT_LANG_BT_OK;
-
- locals_error:
-  do_cleanups (old_chain);
-  return EXT_LANG_BT_ERROR;
 }
 
 /* Helper function for printing frame arguments.  This function
@@ -959,50 +865,43 @@ py_print_args (PyObject *filter,
               enum ext_lang_frame_args args_type,
               struct frame_info *frame)
 {
-  PyObject *args_iter  = get_py_iter_from_func (filter, "frame_args");
-  struct cleanup *old_chain = make_cleanup_py_xdecref (args_iter);
-
+  gdbpy_ref<> args_iter (get_py_iter_from_func (filter, "frame_args"));
   if (args_iter == NULL)
-    goto args_error;
+    return EXT_LANG_BT_ERROR;
 
-  make_cleanup_ui_out_list_begin_end (out, "args");
+  ui_out_emit_list list_emitter (out, "args");
 
   TRY
     {
       annotate_frame_args ();
-      if (! ui_out_is_mi_like_p (out))
-       ui_out_text (out, " (");
+      if (! out->is_mi_like_p ())
+       out->text (" (");
     }
   CATCH (except, RETURN_MASK_ALL)
     {
       gdbpy_convert_exception (except);
-      goto args_error;
+      return EXT_LANG_BT_ERROR;
     }
   END_CATCH
 
-  if (args_iter != Py_None)
-    if (enumerate_args (args_iter, out, args_type, 0, frame)
-       == EXT_LANG_BT_ERROR)
-      goto args_error;
+  if (args_iter != Py_None
+      && (enumerate_args (args_iter.get (), out, args_type, 0, frame)
+         == EXT_LANG_BT_ERROR))
+    return EXT_LANG_BT_ERROR;
 
   TRY
     {
-      if (! ui_out_is_mi_like_p (out))
-       ui_out_text (out, ")");
+      if (! out->is_mi_like_p ())
+       out->text (")");
     }
   CATCH (except, RETURN_MASK_ALL)
     {
       gdbpy_convert_exception (except);
-      goto args_error;
+      return EXT_LANG_BT_ERROR;
     }
   END_CATCH
 
-  do_cleanups (old_chain);
   return EXT_LANG_BT_OK;
-
- args_error:
-  do_cleanups (old_chain);
-  return EXT_LANG_BT_ERROR;
 }
 
 /*  Print a single frame to the designated output stream, detecting
@@ -1029,10 +928,9 @@ py_print_frame (PyObject *filter, int flags,
   CORE_ADDR address = 0;
   struct gdbarch *gdbarch = NULL;
   struct frame_info *frame = NULL;
-  struct cleanup *cleanup_stack;
   struct value_print_options opts;
-  PyObject *py_inf_frame;
   int print_level, print_frame_info, print_args, print_locals;
+  gdb::unique_xmalloc_ptr<char> function_to_free;
 
   /* Extract print settings from FLAGS.  */
   print_level = (flags & PRINT_LEVEL) ? 1 : 0;
@@ -1045,14 +943,12 @@ py_print_frame (PyObject *filter, int flags,
   /* Get the underlying frame.  This is needed to determine GDB
   architecture, and also, in the cases of frame variables/arguments to
   read them if they returned filter object requires us to do so.  */
-  py_inf_frame = PyObject_CallMethod (filter, "inferior_frame", NULL);
+  gdbpy_ref<> py_inf_frame (PyObject_CallMethod (filter, "inferior_frame",
+                                                NULL));
   if (py_inf_frame == NULL)
     return EXT_LANG_BT_ERROR;
 
-  frame = frame_object_to_frame_info (py_inf_frame);;
-
-  Py_DECREF (py_inf_frame);
-
+  frame = frame_object_to_frame_info (py_inf_frame.get ());
   if (frame == NULL)
     return EXT_LANG_BT_ERROR;
 
@@ -1076,12 +972,12 @@ py_print_frame (PyObject *filter, int flags,
       return EXT_LANG_BT_COMPLETED;
     }
 
-  cleanup_stack = make_cleanup (null_cleanup, NULL);
+  gdb::optional<ui_out_emit_tuple> tuple;
 
   /* -stack-list-locals does not require a
      wrapping frame attribute.  */
   if (print_frame_info || (print_args && ! print_locals))
-    make_cleanup_ui_out_tuple_begin_end (out, "frame");
+    tuple.emplace (out, "frame");
 
   if (print_frame_info)
     {
@@ -1091,12 +987,11 @@ py_print_frame (PyObject *filter, int flags,
        {
          TRY
            {
-             ui_out_spaces (out, indent*4);
+             out->spaces (indent * 4);
            }
          CATCH (except, RETURN_MASK_ERROR)
            {
              gdbpy_convert_exception (except);
-             do_cleanups (cleanup_stack);
              return EXT_LANG_BT_ERROR;
            }
          END_CATCH
@@ -1106,26 +1001,18 @@ py_print_frame (PyObject *filter, int flags,
         address printing.  */
       if (PyObject_HasAttrString (filter, "address"))
        {
-         PyObject *paddr = PyObject_CallMethod (filter, "address", NULL);
+         gdbpy_ref<> paddr (PyObject_CallMethod (filter, "address", NULL));
 
          if (paddr == NULL)
-           {
-             do_cleanups (cleanup_stack);
-             return EXT_LANG_BT_ERROR;
-           }
+           return EXT_LANG_BT_ERROR;
 
          if (paddr != Py_None)
            {
-             if (get_addr_from_python (paddr, &address) < 0)
-               {
-                 Py_DECREF (paddr);
-                 do_cleanups (cleanup_stack);
-                 return EXT_LANG_BT_ERROR;
-               }
+             if (get_addr_from_python (paddr.get (), &address) < 0)
+               return EXT_LANG_BT_ERROR;
 
              has_addr = 1;
            }
-         Py_DECREF (paddr);
        }
     }
 
@@ -1147,21 +1034,20 @@ py_print_frame (PyObject *filter, int flags,
             architecture from the eliding frame.  If that is the case, do
             not print 'level', but print spaces.  */
          if (*slot == frame)
-           ui_out_field_skip (out, "level");
+           out->field_skip ("level");
          else
            {
              *slot = frame;
              annotate_frame_begin (print_level ? level : 0,
                                    gdbarch, address);
-             ui_out_text (out, "#");
-             ui_out_field_fmt_int (out, 2, ui_left, "level",
+             out->text ("#");
+             out->field_fmt_int (2, ui_left, "level",
                                    level);
            }
        }
       CATCH (except, RETURN_MASK_ERROR)
        {
          gdbpy_convert_exception (except);
-         do_cleanups (cleanup_stack);
          return EXT_LANG_BT_ERROR;
        }
       END_CATCH
@@ -1176,14 +1062,13 @@ py_print_frame (PyObject *filter, int flags,
          TRY
            {
              annotate_frame_address ();
-             ui_out_field_core_addr (out, "addr", gdbarch, address);
+             out->field_core_addr ("addr", gdbarch, address);
              annotate_frame_address_end ();
-             ui_out_text (out, " in ");
+             out->text (" in ");
            }
          CATCH (except, RETURN_MASK_ERROR)
            {
              gdbpy_convert_exception (except);
-             do_cleanups (cleanup_stack);
              return EXT_LANG_BT_ERROR;
            }
          END_CATCH
@@ -1192,41 +1077,28 @@ py_print_frame (PyObject *filter, int flags,
       /* Print frame function name.  */
       if (PyObject_HasAttrString (filter, "function"))
        {
-         PyObject *py_func = PyObject_CallMethod (filter, "function", NULL);
-         struct cleanup *py_func_cleanup;
+         gdbpy_ref<> py_func (PyObject_CallMethod (filter, "function", NULL));
          const char *function = NULL;
 
          if (py_func == NULL)
-           {
-             do_cleanups (cleanup_stack);
-             return EXT_LANG_BT_ERROR;
-           }
-         py_func_cleanup = make_cleanup_py_decref (py_func);
+           return EXT_LANG_BT_ERROR;
 
-         if (gdbpy_is_string (py_func))
+         if (gdbpy_is_string (py_func.get ()))
            {
-             char *function_to_free;
+             function_to_free = python_string_to_host_string (py_func.get ());
 
-             function = function_to_free =
-               python_string_to_host_string (py_func);
+             if (function_to_free == NULL)
+               return EXT_LANG_BT_ERROR;
 
-             if (function == NULL)
-               {
-                 do_cleanups (cleanup_stack);
-                 return EXT_LANG_BT_ERROR;
-               }
-             make_cleanup (xfree, function_to_free);
+             function = function_to_free.get ();
            }
-         else if (PyLong_Check (py_func))
+         else if (PyLong_Check (py_func.get ()))
            {
              CORE_ADDR addr;
              struct bound_minimal_symbol msymbol;
 
-             if (get_addr_from_python (py_func, &addr) < 0)
-               {
-                 do_cleanups (cleanup_stack);
-                 return EXT_LANG_BT_ERROR;
-               }
+             if (get_addr_from_python (py_func.get (), &addr) < 0)
+               return EXT_LANG_BT_ERROR;
 
              msymbol = lookup_minimal_symbol_by_pc (addr);
              if (msymbol.minsym != NULL)
@@ -1237,7 +1109,6 @@ py_print_frame (PyObject *filter, int flags,
              PyErr_SetString (PyExc_RuntimeError,
                               _("FrameDecorator.function: expecting a " \
                                 "String, integer or None."));
-             do_cleanups (cleanup_stack);
              return EXT_LANG_BT_ERROR;
            }
 
@@ -1245,19 +1116,16 @@ py_print_frame (PyObject *filter, int flags,
            {
              annotate_frame_function_name ();
              if (function == NULL)
-               ui_out_field_skip (out, "func");
+               out->field_skip ("func");
              else
-               ui_out_field_string (out, "func", function);
+               out->field_string ("func", function);
            }
          CATCH (except, RETURN_MASK_ERROR)
            {
              gdbpy_convert_exception (except);
-             do_cleanups (cleanup_stack);
              return EXT_LANG_BT_ERROR;
            }
          END_CATCH
-
-         do_cleanups (py_func_cleanup);
        }
     }
 
@@ -1267,10 +1135,7 @@ py_print_frame (PyObject *filter, int flags,
   if (print_args)
     {
       if (py_print_args (filter, out, args_type, frame) == EXT_LANG_BT_ERROR)
-       {
-         do_cleanups (cleanup_stack);
-         return EXT_LANG_BT_ERROR;
-       }
+       return EXT_LANG_BT_ERROR;
     }
 
   /* File name/source/line number information.  */
@@ -1283,106 +1148,84 @@ py_print_frame (PyObject *filter, int flags,
       CATCH (except, RETURN_MASK_ERROR)
        {
          gdbpy_convert_exception (except);
-         do_cleanups (cleanup_stack);
          return EXT_LANG_BT_ERROR;
        }
       END_CATCH
 
       if (PyObject_HasAttrString (filter, "filename"))
        {
-         PyObject *py_fn = PyObject_CallMethod (filter, "filename", NULL);
-         struct cleanup *py_fn_cleanup;
+         gdbpy_ref<> py_fn (PyObject_CallMethod (filter, "filename", NULL));
 
          if (py_fn == NULL)
-           {
-             do_cleanups (cleanup_stack);
-             return EXT_LANG_BT_ERROR;
-           }
-         py_fn_cleanup = make_cleanup_py_decref (py_fn);
+           return EXT_LANG_BT_ERROR;
 
          if (py_fn != Py_None)
            {
-             char *filename = python_string_to_host_string (py_fn);
+             gdb::unique_xmalloc_ptr<char>
+               filename (python_string_to_host_string (py_fn.get ()));
 
              if (filename == NULL)
-               {
-                 do_cleanups (cleanup_stack);
-                 return EXT_LANG_BT_ERROR;
-               }
+               return EXT_LANG_BT_ERROR;
 
-             make_cleanup (xfree, filename);
              TRY
                {
-                 ui_out_wrap_hint (out, "   ");
-                 ui_out_text (out, " at ");
+                 out->wrap_hint ("   ");
+                 out->text (" at ");
                  annotate_frame_source_file ();
-                 ui_out_field_string (out, "file", filename);
+                 out->field_string ("file", filename.get ());
                  annotate_frame_source_file_end ();
                }
              CATCH (except, RETURN_MASK_ERROR)
                {
                  gdbpy_convert_exception (except);
-                 do_cleanups (cleanup_stack);
                  return EXT_LANG_BT_ERROR;
                }
              END_CATCH
            }
-         do_cleanups (py_fn_cleanup);
        }
 
       if (PyObject_HasAttrString (filter, "line"))
        {
-         PyObject *py_line = PyObject_CallMethod (filter, "line", NULL);
-         struct cleanup *py_line_cleanup;
+         gdbpy_ref<> py_line (PyObject_CallMethod (filter, "line", NULL));
          int line;
 
          if (py_line == NULL)
-           {
-             do_cleanups (cleanup_stack);
-             return EXT_LANG_BT_ERROR;
-           }
-         py_line_cleanup = make_cleanup_py_decref (py_line);
+           return EXT_LANG_BT_ERROR;
 
          if (py_line != Py_None)
            {
-             line = PyLong_AsLong (py_line);
+             line = PyLong_AsLong (py_line.get ());
              if (PyErr_Occurred ())
-               {
-                 do_cleanups (cleanup_stack);
-                 return EXT_LANG_BT_ERROR;
-               }
+               return EXT_LANG_BT_ERROR;
 
              TRY
                {
-                 ui_out_text (out, ":");
+                 out->text (":");
                  annotate_frame_source_line ();
-                 ui_out_field_int (out, "line", line);
+                 out->field_int ("line", line);
                }
              CATCH (except, RETURN_MASK_ERROR)
                {
                  gdbpy_convert_exception (except);
-                 do_cleanups (cleanup_stack);
                  return EXT_LANG_BT_ERROR;
                }
              END_CATCH
            }
-         do_cleanups (py_line_cleanup);
        }
     }
 
   /* For MI we need to deal with the "children" list population of
      elided frames, so if MI output detected do not send newline.  */
-  if (! ui_out_is_mi_like_p (out))
+  if (! out->is_mi_like_p ())
     {
       TRY
        {
          annotate_frame_end ();
-         ui_out_text (out, "\n");
+         out->text ("\n");
        }
       CATCH (except, RETURN_MASK_ERROR)
        {
          gdbpy_convert_exception (except);
-         do_cleanups (cleanup_stack);
          return EXT_LANG_BT_ERROR;
        }
       END_CATCH
@@ -1392,61 +1235,41 @@ py_print_frame (PyObject *filter, int flags,
     {
       if (py_print_locals (filter, out, args_type, indent,
                           frame) == EXT_LANG_BT_ERROR)
-       {
-         do_cleanups (cleanup_stack);
-         return EXT_LANG_BT_ERROR;
-       }
+       return EXT_LANG_BT_ERROR;
     }
 
   {
-    PyObject *elided;
-    struct cleanup *elided_cleanup;
-
     /* Finally recursively print elided frames, if any.  */
-    elided = get_py_iter_from_func (filter, "elided");
+    gdbpy_ref<> elided (get_py_iter_from_func (filter, "elided"));
     if (elided == NULL)
-      {
-       do_cleanups (cleanup_stack);
-       return EXT_LANG_BT_ERROR;
-      }
-    elided_cleanup = make_cleanup_py_decref (elided);
+      return EXT_LANG_BT_ERROR;
 
     if (elided != Py_None)
       {
        PyObject *item;
 
-       make_cleanup_ui_out_list_begin_end (out, "children");
+       ui_out_emit_list inner_list_emiter (out, "children");
 
-       if (! ui_out_is_mi_like_p (out))
+       if (! out->is_mi_like_p ())
          indent++;
 
-       while ((item = PyIter_Next (elided)))
+       while ((item = PyIter_Next (elided.get ())))
          {
-           struct cleanup *item_cleanup = make_cleanup_py_decref (item);
+           gdbpy_ref<> item_ref (item);
 
            enum ext_lang_bt_status success = py_print_frame (item, flags,
                                                              args_type, out,
                                                              indent,
                                                              levels_printed);
 
-           do_cleanups (item_cleanup);
-
            if (success == EXT_LANG_BT_ERROR)
-             {
-               do_cleanups (cleanup_stack);
-               return EXT_LANG_BT_ERROR;
-             }
+             return EXT_LANG_BT_ERROR;
          }
        if (item == NULL && PyErr_Occurred ())
-         {
-           do_cleanups (cleanup_stack);
-           return EXT_LANG_BT_ERROR;
-         }
+         return EXT_LANG_BT_ERROR;
       }
-    do_cleanups (elided_cleanup);
   }
 
-  do_cleanups (cleanup_stack);
   return EXT_LANG_BT_COMPLETED;
 }
 
@@ -1457,60 +1280,39 @@ static PyObject *
 bootstrap_python_frame_filters (struct frame_info *frame,
                                int frame_low, int frame_high)
 {
-  struct cleanup *cleanups =
-    make_cleanup (null_cleanup, NULL);
-  PyObject *module, *sort_func, *iterable, *frame_obj, *iterator;
-  PyObject *py_frame_low, *py_frame_high;
-
-  frame_obj = frame_info_to_frame_object (frame);
+  gdbpy_ref<> frame_obj (frame_info_to_frame_object (frame));
   if (frame_obj == NULL)
-    goto error;
-  make_cleanup_py_decref (frame_obj);
+    return NULL;
 
-  module = PyImport_ImportModule ("gdb.frames");
+  gdbpy_ref<> module (PyImport_ImportModule ("gdb.frames"));
   if (module == NULL)
-    goto error;
-  make_cleanup_py_decref (module);
+    return NULL;
 
-  sort_func = PyObject_GetAttrString (module, "execute_frame_filters");
+  gdbpy_ref<> sort_func (PyObject_GetAttrString (module.get (),
+                                                "execute_frame_filters"));
   if (sort_func == NULL)
-    goto error;
-  make_cleanup_py_decref (sort_func);
+    return NULL;
 
-  py_frame_low = PyInt_FromLong (frame_low);
+  gdbpy_ref<> py_frame_low (PyInt_FromLong (frame_low));
   if (py_frame_low == NULL)
-    goto error;
-  make_cleanup_py_decref (py_frame_low);
+    return NULL;
 
-  py_frame_high = PyInt_FromLong (frame_high);
+  gdbpy_ref<> py_frame_high (PyInt_FromLong (frame_high));
   if (py_frame_high == NULL)
-    goto error;
-  make_cleanup_py_decref (py_frame_high);
+    return NULL;
 
-  iterable = PyObject_CallFunctionObjArgs (sort_func, frame_obj,
-                                          py_frame_low,
-                                          py_frame_high,
-                                          NULL);
+  gdbpy_ref<> iterable (PyObject_CallFunctionObjArgs (sort_func.get (),
+                                                     frame_obj.get (),
+                                                     py_frame_low.get (),
+                                                     py_frame_high.get (),
+                                                     NULL));
   if (iterable == NULL)
-    goto error;
-
-  do_cleanups (cleanups);
+    return NULL;
 
   if (iterable != Py_None)
-    {
-      iterator = PyObject_GetIter (iterable);
-      Py_DECREF (iterable);
-    }
+    return PyObject_GetIter (iterable.get ());
   else
-    {
-      return iterable;
-    }
-
-  return iterator;
-
- error:
-  do_cleanups (cleanups);
-  return NULL;
+    return iterable.release ();
 }
 
 /*  This is the only publicly exported function in this file.  FRAME
@@ -1535,11 +1337,7 @@ gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
                          struct ui_out *out, int frame_low, int frame_high)
 {
   struct gdbarch *gdbarch = NULL;
-  struct cleanup *cleanups;
   enum ext_lang_bt_status success = EXT_LANG_BT_ERROR;
-  PyObject *iterable;
-  PyObject *item;
-  htab_t levels_printed;
 
   if (!gdb_python_initialized)
     return EXT_LANG_BT_NO_FILTERS;
@@ -1555,9 +1353,22 @@ gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
     }
   END_CATCH
 
-  cleanups = ensure_python_env (gdbarch, current_language);
+  gdbpy_enter enter_py (gdbarch, current_language);
+
+  /* When we're limiting the number of frames, be careful to request
+     one extra frame, so that we can print a message if there are more
+     frames.  */
+  int frame_countdown = -1;
+  if ((flags & PRINT_MORE_FRAMES) != 0 && frame_low >= 0 && frame_high >= 0)
+    {
+      ++frame_high;
+      /* This has an extra +1 because it is checked before a frame is
+        printed.  */
+      frame_countdown = frame_high - frame_low + 1;
+    }
 
-  iterable = bootstrap_python_frame_filters (frame, frame_low, frame_high);
+  gdbpy_ref<> iterable (bootstrap_python_frame_filters (frame, frame_low,
+                                                       frame_high));
 
   if (iterable == NULL)
     {
@@ -1575,34 +1386,49 @@ gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
         default backtrace.  */
 
       gdbpy_print_stack ();
-      do_cleanups (cleanups);
       return EXT_LANG_BT_NO_FILTERS;
     }
 
   /* If iterable is None, then there are no frame filters registered.
      If this is the case, defer to default GDB printing routines in MI
      and CLI.  */
-  make_cleanup_py_decref (iterable);
   if (iterable == Py_None)
-    {
-      success = EXT_LANG_BT_NO_FILTERS;
-      goto done;
-    }
+    return EXT_LANG_BT_NO_FILTERS;
 
-  levels_printed = htab_create (20,
-                               htab_hash_pointer,
-                               htab_eq_pointer,
-                               NULL);
-  make_cleanup_htab_delete (levels_printed);
+  htab_up levels_printed (htab_create (20,
+                                      htab_hash_pointer,
+                                      htab_eq_pointer,
+                                      NULL));
 
-  while ((item = PyIter_Next (iterable)))
+  while (true)
     {
-      struct cleanup *item_cleanup = make_cleanup_py_decref (item);
+      gdbpy_ref<> item (PyIter_Next (iterable.get ()));
 
-      success = py_print_frame (item, flags, args_type, out, 0,
-                               levels_printed);
+      if (item == NULL)
+       {
+         if (PyErr_Occurred ())
+           {
+             gdbpy_print_stack ();
+             return EXT_LANG_BT_ERROR;
+           }
+         break;
+       }
+
+      if (frame_countdown != -1)
+       {
+         gdb_assert ((flags & PRINT_MORE_FRAMES) != 0);
+         --frame_countdown;
+         if (frame_countdown == 0)
+           {
+             /* We've printed all the frames we were asked to
+                print, but more frames existed.  */
+             printf_filtered (_("(More stack frames follow...)\n"));
+             break;
+           }
+       }
 
-      do_cleanups (item_cleanup);
+      success = py_print_frame (item.get (), flags, args_type, out, 0,
+                               levels_printed.get ());
 
       /* Do not exit on error printing a single frame.  Print the
         error and continue with other frames.  */
@@ -1610,17 +1436,5 @@ gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
        gdbpy_print_stack ();
     }
 
-  if (item == NULL && PyErr_Occurred ())
-    goto error;
-
- done:
-  do_cleanups (cleanups);
   return success;
-
-  /* Exit and abandon backtrace on error, printing the exception that
-     is set.  */
- error:
-  gdbpy_print_stack ();
-  do_cleanups (cleanups);
-  return EXT_LANG_BT_ERROR;
 }
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