[PATCH v2 0/3] Improvements to Python parameters

[PATCH v2 0/3] Improvements to Python parameters

[Tom Tromey]

Here's v2 of the series to improve Python parameters in a few ways.

v1 is here:

    https://sourceware.org/pipermail/gdb-patches/2022-January/184826.html

I think this fixes all the review comments.

Tom

[PATCH v2 1/3] Change how Python architecture and language are handled

[Tom Tromey]

Currently, gdb's Python layer captures the current architecture and
language when "entering" Python code.  This has some undesirable
effects, and so this series changes how this is handled.

First, there is code like this:

  gdbpy_enter enter_py (python_gdbarch, python_language);

This is incorrect, because both of these are NULL when not otherwise
assigned.  This can cause crashes in some cases -- I've added one to
the test suite.  (Note that this crasher is just an example, other
ones along the same lines are possible.)

Second, when the language is captured in this way, it means that
Python code cannot affect the current language for its own purposes.
It's reasonable to want to write code like this:

    gdb.execute('set language mumble')
    ... stuff using the current language
    gdb.execute('set language previous-value')

However, this won't actually work, because the language is captured on
entry.  I've added a test to show this as well.

This patch changes gdb to try to avoid capturing the current values.
The Python concept of the current gdbarch is only set in those few
cases where a non-default value is computed or needed; and the
language is not captured at all -- instead, in the cases where it's
required, the current language is temporarily changed.
---
 gdb/python/py-breakpoint.c                  | 19 ++-----
 gdb/python/py-cmd.c                         |  8 +--
 gdb/python/py-connection.c                  |  2 +-
 gdb/python/py-finishbreakpoint.c            |  6 +-
 gdb/python/py-framefilter.c                 | 12 ++--
 gdb/python/py-inferior.c                    | 27 +++++----
 gdb/python/py-membuf.c                      |  3 +-
 gdb/python/py-objfile.c                     |  2 +-
 gdb/python/py-param.c                       |  4 +-
 gdb/python/py-progspace.c                   |  2 +-
 gdb/python/py-tui.c                         | 18 +++---
 gdb/python/py-type.c                        |  4 +-
 gdb/python/py-unwind.c                      |  2 +-
 gdb/python/py-utils.c                       | 10 ++--
 gdb/python/py-value.c                       | 21 ++++---
 gdb/python/py-xmethods.c                    | 12 ++--
 gdb/python/python-internal.h                | 27 +++++++--
 gdb/python/python.c                         | 62 +++++++++++++--------
 gdb/testsuite/gdb.python/py-inferior.exp    |  2 +
 gdb/testsuite/gdb.python/py-lookup-type.exp |  8 +++
 20 files changed, 146 insertions(+), 105 deletions(-)

diff --git a/gdb/python/py-breakpoint.c b/gdb/python/py-breakpoint.c
index f00bd6f78e6..2fc20376af8 100644
--- a/gdb/python/py-breakpoint.c
+++ b/gdb/python/py-breakpoint.c
@@ -858,7 +858,7 @@ bppy_init (PyObject *self, PyObject *args, PyObject *kwargs)
 	    const struct breakpoint_ops *ops =
 	      breakpoint_ops_for_event_location (location.get (), false);
 
-	    create_breakpoint (python_gdbarch,
+	    create_breakpoint (gdbpy_enter::get_gdbarch (),
 			       location.get (), NULL, -1, NULL, false,
 			       0,
 			       temporary_bp, type,
@@ -954,15 +954,13 @@ gdbpy_breakpoint_cond_says_stop (const struct extension_language_defn *extlang,
   int stop;
   struct gdbpy_breakpoint_object *bp_obj = b->py_bp_object;
   PyObject *py_bp = (PyObject *) bp_obj;
-  struct gdbarch *garch;
 
   if (bp_obj == NULL)
     return EXT_LANG_BP_STOP_UNSET;
 
   stop = -1;
-  garch = b->gdbarch ? b->gdbarch : get_current_arch ();
 
-  gdbpy_enter enter_py (garch, current_language);
+  gdbpy_enter enter_py (b->gdbarch);
 
   if (bp_obj->is_finish_bp)
     bpfinishpy_pre_stop_hook (bp_obj);
@@ -1005,15 +1003,13 @@ gdbpy_breakpoint_has_cond (const struct extension_language_defn *extlang,
 			   struct breakpoint *b)
 {
   PyObject *py_bp;
-  struct gdbarch *garch;
 
   if (b->py_bp_object == NULL)
     return 0;
 
   py_bp = (PyObject *) b->py_bp_object;
-  garch = b->gdbarch ? b->gdbarch : get_current_arch ();
 
-  gdbpy_enter enter_py (garch, current_language);
+  gdbpy_enter enter_py (b->gdbarch);
   return PyObject_HasAttrString (py_bp, stop_func);
 }
 
@@ -1048,8 +1044,7 @@ gdbpy_breakpoint_created (struct breakpoint *bp)
       return;
     }
 
-  struct gdbarch *garch = bp->gdbarch ? bp->gdbarch : get_current_arch ();
-  gdbpy_enter enter_py (garch, current_language);
+  gdbpy_enter enter_py (bp->gdbarch);
 
   if (bppy_pending_object)
     {
@@ -1099,8 +1094,7 @@ gdbpy_breakpoint_deleted (struct breakpoint *b)
   bp = get_breakpoint (num);
   if (bp)
     {
-      struct gdbarch *garch = bp->gdbarch ? bp->gdbarch : get_current_arch ();
-      gdbpy_enter enter_py (garch, current_language);
+      gdbpy_enter enter_py (b->gdbarch);
 
       gdbpy_ref<gdbpy_breakpoint_object> bp_obj (bp->py_bp_object);
       if (bp_obj != NULL)
@@ -1131,8 +1125,7 @@ gdbpy_breakpoint_modified (struct breakpoint *b)
   bp = get_breakpoint (num);
   if (bp)
     {
-      struct gdbarch *garch = bp->gdbarch ? bp->gdbarch : get_current_arch ();
-      gdbpy_enter enter_py (garch, current_language);
+      gdbpy_enter enter_py (b->gdbarch);
 
       PyObject *bp_obj = (PyObject *) bp->py_bp_object;
       if (bp_obj)
diff --git a/gdb/python/py-cmd.c b/gdb/python/py-cmd.c
index 3a4e6490cf0..b51b05c95ad 100644
--- a/gdb/python/py-cmd.c
+++ b/gdb/python/py-cmd.c
@@ -90,7 +90,7 @@ cmdpy_dont_repeat (PyObject *self, PyObject *args)
 static void
 cmdpy_destroyer (struct cmd_list_element *self, void *context)
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   /* Release our hold on the command object.  */
   gdbpy_ref<cmdpy_object> cmd ((cmdpy_object *) context);
@@ -104,7 +104,7 @@ cmdpy_function (const char *args, int from_tty, cmd_list_element *command)
 {
   cmdpy_object *obj = (cmdpy_object *) command->context ();
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   if (! obj)
     error (_("Invalid invocation of Python command object."));
@@ -223,7 +223,7 @@ cmdpy_completer_handle_brkchars (struct cmd_list_element *command,
 				 completion_tracker &tracker,
 				 const char *text, const char *word)
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   /* Calling our helper to obtain a reference to the PyObject of the Python
      function.  */
@@ -266,7 +266,7 @@ cmdpy_completer (struct cmd_list_element *command,
 		 completion_tracker &tracker,
 		 const char *text, const char *word)
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   /* Calling our helper to obtain a reference to the PyObject of the Python
      function.  */
diff --git a/gdb/python/py-connection.c b/gdb/python/py-connection.c
index 7c33a1f93d4..4cdd6abbf3d 100644
--- a/gdb/python/py-connection.c
+++ b/gdb/python/py-connection.c
@@ -161,7 +161,7 @@ connpy_connection_removed (process_stratum_target *target)
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   if (!evregpy_no_listeners_p (gdb_py_events.connection_removed))
     if (emit_connection_event (target, gdb_py_events.connection_removed) < 0)
diff --git a/gdb/python/py-finishbreakpoint.c b/gdb/python/py-finishbreakpoint.c
index 8d5eb42efc0..03bd4934506 100644
--- a/gdb/python/py-finishbreakpoint.c
+++ b/gdb/python/py-finishbreakpoint.c
@@ -293,7 +293,7 @@ bpfinishpy_init (PyObject *self, PyObject *args, PyObject *kwargs)
       /* Set a breakpoint on the return address.  */
       event_location_up location
 	= new_address_location (get_frame_pc (prev_frame), NULL, 0);
-      create_breakpoint (python_gdbarch,
+      create_breakpoint (gdbpy_enter::get_gdbarch (),
 			 location.get (), NULL, thread, NULL, false,
 			 0,
 			 1 /*temp_flag*/,
@@ -380,7 +380,7 @@ bpfinishpy_detect_out_scope_cb (struct breakpoint *b,
 static void
 bpfinishpy_handle_stop (struct bpstat *bs, int print_frame)
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   for (breakpoint *bp : all_breakpoints_safe ())
     bpfinishpy_detect_out_scope_cb (bp, bs == NULL ? NULL : bs->breakpoint_at);
@@ -392,7 +392,7 @@ bpfinishpy_handle_stop (struct bpstat *bs, int print_frame)
 static void
 bpfinishpy_handle_exit (struct inferior *inf)
 {
-  gdbpy_enter enter_py (target_gdbarch (), current_language);
+  gdbpy_enter enter_py (target_gdbarch ());
 
   for (breakpoint *bp : all_breakpoints_safe ())
     bpfinishpy_detect_out_scope_cb (bp, nullptr);
diff --git a/gdb/python/py-framefilter.c b/gdb/python/py-framefilter.c
index 936354f354c..7870374b3ec 100644
--- a/gdb/python/py-framefilter.c
+++ b/gdb/python/py-framefilter.c
@@ -74,11 +74,11 @@ extract_sym (PyObject *obj, gdb::unique_xmalloc_ptr<char> *name,
       if (*name == NULL)
 	return EXT_LANG_BT_ERROR;
       /* If the API returns a string (and not a symbol), then there is
-	no symbol derived language available and the frame filter has
-	either overridden the symbol with a string, or supplied a
-	entirely synthetic symbol/value pairing.  In that case, use
-	python_language.  */
-      *language = python_language;
+	 no symbol derived language available and the frame filter has
+	 either overridden the symbol with a string, or supplied a
+	 entirely synthetic symbol/value pairing.  In that case, use
+	 the current language.  */
+      *language = current_language;
       *sym = NULL;
       *sym_block = NULL;
     }
@@ -1157,7 +1157,7 @@ gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
       return EXT_LANG_BT_NO_FILTERS;
     }
 
-  gdbpy_enter enter_py (gdbarch, current_language);
+  gdbpy_enter enter_py (gdbarch);
 
   /* 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
diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index 45e33f9e28a..46f0c9ffd04 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -86,7 +86,7 @@ python_on_normal_stop (struct bpstat *bs, int print_frame)
 
   stop_signal = inferior_thread ()->stop_signal ();
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   if (emit_stop_event (bs, stop_signal) < 0)
     gdbpy_print_stack ();
@@ -98,7 +98,7 @@ python_on_resume (ptid_t ptid)
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (target_gdbarch (), current_language);
+  gdbpy_enter enter_py (target_gdbarch ());
 
   if (emit_continue_event (ptid) < 0)
     gdbpy_print_stack ();
@@ -110,7 +110,7 @@ python_on_resume (ptid_t ptid)
 static void
 python_on_inferior_call_pre (ptid_t thread, CORE_ADDR address)
 {
-  gdbpy_enter enter_py (target_gdbarch (), current_language);
+  gdbpy_enter enter_py (target_gdbarch ());
 
   if (emit_inferior_call_event (INFERIOR_CALL_PRE, thread, address) < 0)
     gdbpy_print_stack ();
@@ -122,7 +122,7 @@ python_on_inferior_call_pre (ptid_t thread, CORE_ADDR address)
 static void
 python_on_inferior_call_post (ptid_t thread, CORE_ADDR address)
 {
-  gdbpy_enter enter_py (target_gdbarch (), current_language);
+  gdbpy_enter enter_py (target_gdbarch ());
 
   if (emit_inferior_call_event (INFERIOR_CALL_POST, thread, address) < 0)
     gdbpy_print_stack ();
@@ -135,7 +135,7 @@ python_on_inferior_call_post (ptid_t thread, CORE_ADDR address)
 static void
 python_on_memory_change (struct inferior *inferior, CORE_ADDR addr, ssize_t len, const bfd_byte *data)
 {
-  gdbpy_enter enter_py (target_gdbarch (), current_language);
+  gdbpy_enter enter_py (target_gdbarch ());
 
   if (emit_memory_changed_event (addr, len) < 0)
     gdbpy_print_stack ();
@@ -148,7 +148,7 @@ python_on_memory_change (struct inferior *inferior, CORE_ADDR addr, ssize_t len,
 static void
 python_on_register_change (struct frame_info *frame, int regnum)
 {
-  gdbpy_enter enter_py (target_gdbarch (), current_language);
+  gdbpy_enter enter_py (target_gdbarch ());
 
   if (emit_register_changed_event (frame, regnum) < 0)
     gdbpy_print_stack ();
@@ -162,7 +162,7 @@ python_inferior_exit (struct inferior *inf)
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (target_gdbarch (), current_language);
+  gdbpy_enter enter_py (target_gdbarch ());
 
   if (inf->has_exit_code)
     exit_code = &inf->exit_code;
@@ -183,8 +183,7 @@ python_new_objfile (struct objfile *objfile)
 
   gdbpy_enter enter_py (objfile != NULL
 			? objfile->arch ()
-			: target_gdbarch (),
-			current_language);
+			: target_gdbarch ());
 
   if (objfile == NULL)
     {
@@ -237,7 +236,7 @@ python_new_inferior (struct inferior *inf)
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (python_gdbarch, python_language);
+  gdbpy_enter enter_py;
 
   if (evregpy_no_listeners_p (gdb_py_events.new_inferior))
     return;
@@ -265,7 +264,7 @@ python_inferior_deleted (struct inferior *inf)
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (python_gdbarch, python_language);
+  gdbpy_enter enter_py;
 
   if (evregpy_no_listeners_p (gdb_py_events.inferior_deleted))
     return;
@@ -312,7 +311,7 @@ add_thread_object (struct thread_info *tp)
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (python_gdbarch, python_language);
+  gdbpy_enter enter_py;
 
   gdbpy_ref<thread_object> thread_obj = create_thread_object (tp);
   if (thread_obj == NULL)
@@ -348,7 +347,7 @@ delete_thread_object (struct thread_info *tp, int ignore)
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (python_gdbarch, python_language);
+  gdbpy_enter enter_py;
 
   gdbpy_ref<inferior_object> inf_obj = inferior_to_inferior_object (tp->inf);
   if (inf_obj == NULL)
@@ -792,7 +791,7 @@ py_free_inferior (struct inferior *inf, void *datum)
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (python_gdbarch, python_language);
+  gdbpy_enter enter_py;
   gdbpy_ref<inferior_object> inf_obj ((inferior_object *) datum);
 
   inf_obj->inferior = NULL;
diff --git a/gdb/python/py-membuf.c b/gdb/python/py-membuf.c
index e789a78e649..74cc0fb46bd 100644
--- a/gdb/python/py-membuf.c
+++ b/gdb/python/py-membuf.c
@@ -83,7 +83,8 @@ mbpy_str (PyObject *self)
 
   return PyString_FromFormat (_("Memory buffer for address %s, \
 which is %s bytes long."),
-			      paddress (python_gdbarch, membuf_obj->addr),
+			      paddress (gdbpy_enter::get_gdbarch (),
+					membuf_obj->addr),
 			      pulongest (membuf_obj->length));
 }
 
diff --git a/gdb/python/py-objfile.c b/gdb/python/py-objfile.c
index 38052245bde..6055a42260b 100644
--- a/gdb/python/py-objfile.c
+++ b/gdb/python/py-objfile.c
@@ -661,7 +661,7 @@ gdbpy_lookup_objfile (PyObject *self, PyObject *args, PyObject *kw)
 static void
 py_free_objfile (struct objfile *objfile, void *datum)
 {
-  gdbpy_enter enter_py (objfile->arch (), current_language);
+  gdbpy_enter enter_py (objfile->arch ());
   gdbpy_ref<objfile_object> object ((objfile_object *) datum);
   object->objfile = NULL;
 }
diff --git a/gdb/python/py-param.c b/gdb/python/py-param.c
index 592ecbb41f9..8559bc997ea 100644
--- a/gdb/python/py-param.c
+++ b/gdb/python/py-param.c
@@ -396,7 +396,7 @@ get_set_value (const char *args, int from_tty,
   PyObject *obj = (PyObject *) c->context ();
   gdb::unique_xmalloc_ptr<char> set_doc_string;
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
   gdbpy_ref<> set_doc_func (PyString_FromString ("get_set_string"));
 
   if (set_doc_func == NULL)
@@ -431,7 +431,7 @@ get_show_value (struct ui_file *file, int from_tty,
   PyObject *obj = (PyObject *) c->context ();
   gdb::unique_xmalloc_ptr<char> show_doc_string;
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
   gdbpy_ref<> show_doc_func (PyString_FromString ("get_show_string"));
 
   if (show_doc_func == NULL)
diff --git a/gdb/python/py-progspace.c b/gdb/python/py-progspace.c
index 8131b66d24b..b27ebf4a666 100644
--- a/gdb/python/py-progspace.c
+++ b/gdb/python/py-progspace.c
@@ -472,7 +472,7 @@ py_free_pspace (struct program_space *pspace, void *datum)
      being deleted.  */
   struct gdbarch *arch = target_gdbarch ();
 
-  gdbpy_enter enter_py (arch, current_language);
+  gdbpy_enter enter_py (arch);
   gdbpy_ref<pspace_object> object ((pspace_object *) datum);
   object->pspace = NULL;
 }
diff --git a/gdb/python/py-tui.c b/gdb/python/py-tui.c
index 97fdfe2be96..6a92251a705 100644
--- a/gdb/python/py-tui.c
+++ b/gdb/python/py-tui.c
@@ -155,7 +155,7 @@ gdbpy_tui_window::is_valid () const
 
 tui_py_window::~tui_py_window ()
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   /* This can be null if the user-provided Python construction
      function failed.  */
@@ -181,7 +181,7 @@ tui_py_window::rerender ()
 {
   tui_win_info::rerender ();
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   int h = viewport_height ();
   int w = viewport_width ();
@@ -206,7 +206,7 @@ tui_py_window::rerender ()
 void
 tui_py_window::do_scroll_horizontal (int num_to_scroll)
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   if (PyObject_HasAttrString (m_window.get (), "hscroll"))
     {
@@ -220,7 +220,7 @@ tui_py_window::do_scroll_horizontal (int num_to_scroll)
 void
 tui_py_window::do_scroll_vertical (int num_to_scroll)
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   if (PyObject_HasAttrString (m_window.get (), "vscroll"))
     {
@@ -234,7 +234,7 @@ tui_py_window::do_scroll_vertical (int num_to_scroll)
 void
 tui_py_window::click (int mouse_x, int mouse_y, int mouse_button)
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   if (PyObject_HasAttrString (m_window.get (), "click"))
     {
@@ -285,7 +285,7 @@ class gdbpy_tui_window_maker
 
   gdbpy_tui_window_maker (const gdbpy_tui_window_maker &other)
   {
-    gdbpy_enter enter_py (get_current_arch (), current_language);
+    gdbpy_enter enter_py;
     m_constr = other.m_constr;
   }
 
@@ -297,7 +297,7 @@ class gdbpy_tui_window_maker
 
   gdbpy_tui_window_maker &operator= (const gdbpy_tui_window_maker &other)
   {
-    gdbpy_enter enter_py (get_current_arch (), current_language);
+    gdbpy_enter enter_py;
     m_constr = other.m_constr;
     return *this;
   }
@@ -312,14 +312,14 @@ class gdbpy_tui_window_maker
 
 gdbpy_tui_window_maker::~gdbpy_tui_window_maker ()
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
   m_constr.reset (nullptr);
 }
 
 tui_win_info *
 gdbpy_tui_window_maker::operator() (const char *win_name)
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   gdbpy_ref<gdbpy_tui_window> wrapper
     (PyObject_New (gdbpy_tui_window, &gdbpy_tui_window_object_type));
diff --git a/gdb/python/py-type.c b/gdb/python/py-type.c
index 220b0d46ffb..e71e635ecdf 100644
--- a/gdb/python/py-type.c
+++ b/gdb/python/py-type.c
@@ -799,7 +799,7 @@ typy_lookup_typename (const char *type_name, const struct block *block)
       else if (startswith (type_name, "enum "))
 	type = lookup_enum (type_name + 5, NULL);
       else
-	type = lookup_typename (python_language,
+	type = lookup_typename (current_language,
 				type_name, block, 0);
     }
   catch (const gdb_exception &except)
@@ -1089,7 +1089,7 @@ save_objfile_types (struct objfile *objfile, void *datum)
 
   /* This prevents another thread from freeing the objects we're
      operating on.  */
-  gdbpy_enter enter_py (objfile->arch (), current_language);
+  gdbpy_enter enter_py (objfile->arch ());
 
   htab_up copied_types = create_copied_types_hash (objfile);
 
diff --git a/gdb/python/py-unwind.c b/gdb/python/py-unwind.c
index a884c83ec26..3f10122860e 100644
--- a/gdb/python/py-unwind.c
+++ b/gdb/python/py-unwind.c
@@ -524,7 +524,7 @@ pyuw_sniffer (const struct frame_unwind *self, struct frame_info *this_frame,
   struct gdbarch *gdbarch = (struct gdbarch *) (self->unwind_data);
   cached_frame_info *cached_frame;
 
-  gdbpy_enter enter_py (gdbarch, current_language);
+  gdbpy_enter enter_py (gdbarch);
 
   pyuw_debug_printf ("frame=%d, sp=%s, pc=%s",
 		     frame_relative_level (this_frame),
diff --git a/gdb/python/py-utils.c b/gdb/python/py-utils.c
index 79e1c013261..73c860bcc96 100644
--- a/gdb/python/py-utils.c
+++ b/gdb/python/py-utils.c
@@ -93,8 +93,9 @@ unicode_to_encoded_python_string (PyObject *unicode_str, const char *charset)
 gdb::unique_xmalloc_ptr<char>
 unicode_to_target_string (PyObject *unicode_str)
 {
-  return unicode_to_encoded_string (unicode_str,
-				    target_charset (python_gdbarch));
+  return (unicode_to_encoded_string
+	  (unicode_str,
+	   target_charset (gdbpy_enter::get_gdbarch ())));
 }
 
 /* Returns a PyObject with the contents of the given unicode string
@@ -104,8 +105,9 @@ unicode_to_target_string (PyObject *unicode_str)
 static gdbpy_ref<>
 unicode_to_target_python_string (PyObject *unicode_str)
 {
-  return unicode_to_encoded_python_string (unicode_str,
-					   target_charset (python_gdbarch));
+  return (unicode_to_encoded_python_string
+	  (unicode_str,
+	   target_charset (gdbpy_enter::get_gdbarch ())));
 }
 
 /* Converts a python string (8-bit or unicode) to a target string in
diff --git a/gdb/python/py-value.c b/gdb/python/py-value.c
index 70b33d5a27b..d6ceb54fed8 100644
--- a/gdb/python/py-value.c
+++ b/gdb/python/py-value.c
@@ -35,23 +35,26 @@
    GDB (which uses target arithmetic).  */
 
 /* Python's integer type corresponds to C's long type.  */
-#define builtin_type_pyint builtin_type (python_gdbarch)->builtin_long
+#define builtin_type_pyint \
+  builtin_type (gdbpy_enter::get_gdbarch ())->builtin_long
 
 /* Python's float type corresponds to C's double type.  */
-#define builtin_type_pyfloat builtin_type (python_gdbarch)->builtin_double
+#define builtin_type_pyfloat \
+  builtin_type (gdbpy_enter::get_gdbarch ())->builtin_double
 
 /* Python's long type corresponds to C's long long type.  */
-#define builtin_type_pylong builtin_type (python_gdbarch)->builtin_long_long
+#define builtin_type_pylong \
+  builtin_type (gdbpy_enter::get_gdbarch ())->builtin_long_long
 
 /* Python's long type corresponds to C's long long type.  Unsigned version.  */
 #define builtin_type_upylong builtin_type \
-  (python_gdbarch)->builtin_unsigned_long_long
+  (gdbpy_enter::get_gdbarch ())->builtin_unsigned_long_long
 
 #define builtin_type_pybool \
-  language_bool_type (python_language, python_gdbarch)
+  language_bool_type (current_language, gdbpy_enter::get_gdbarch ())
 
 #define builtin_type_pychar \
-  language_string_char_type (python_language, python_gdbarch)
+  language_string_char_type (current_language, gdbpy_enter::get_gdbarch ())
 
 struct value_object {
   PyObject_HEAD
@@ -754,7 +757,7 @@ valpy_format_string (PyObject *self, PyObject *args, PyObject *kw)
   try
     {
       common_val_print (((value_object *) self)->value, &stb, 0,
-			&opts, python_language);
+			&opts, current_language);
     }
   catch (const gdb_exception &except)
     {
@@ -1160,7 +1163,7 @@ valpy_str (PyObject *self)
   try
     {
       common_val_print (((value_object *) self)->value, &stb, 0,
-			&opts, python_language);
+			&opts, current_language);
     }
   catch (const gdb_exception &except)
     {
@@ -2025,7 +2028,7 @@ gdbpy_convenience_variable (PyObject *self, PyObject *args)
 
       if (var != NULL)
 	{
-	  res_val = value_of_internalvar (python_gdbarch, var);
+	  res_val = value_of_internalvar (gdbpy_enter::get_gdbarch (), var);
 	  if (value_type (res_val)->code () == TYPE_CODE_VOID)
 	    res_val = NULL;
 	}
diff --git a/gdb/python/py-xmethods.c b/gdb/python/py-xmethods.c
index fd3673029a0..9d5824962b1 100644
--- a/gdb/python/py-xmethods.c
+++ b/gdb/python/py-xmethods.c
@@ -69,7 +69,7 @@ struct python_xmethod_worker : xmethod_worker
 python_xmethod_worker::~python_xmethod_worker ()
 {
   /* We don't do much here, but we still need the GIL.  */
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   Py_DECREF (m_py_worker);
   Py_DECREF (m_this_type);
@@ -122,7 +122,7 @@ gdbpy_get_matching_xmethod_workers
 {
   gdb_assert (obj_type != NULL && method_name != NULL);
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   gdbpy_ref<> py_type (type_to_type_object (obj_type));
   if (py_type == NULL)
@@ -294,7 +294,7 @@ python_xmethod_worker::do_get_arg_types (std::vector<type *> *arg_types)
 {
   /* The gdbpy_enter object needs to be placed first, so that it's the last to
      be destroyed.  */
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
   struct type *obj_type;
   int i = 1, arg_count;
   gdbpy_ref<> list_iter;
@@ -410,7 +410,7 @@ python_xmethod_worker::do_get_result_type (value *obj,
   struct type *obj_type, *this_type;
   int i;
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   /* First see if there is a get_result_type method.
      If not this could be an old xmethod (pre 7.9.1).  */
@@ -502,7 +502,7 @@ struct value *
 python_xmethod_worker::invoke (struct value *obj,
 			       gdb::array_view<value *> args)
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   int i;
   struct type *obj_type, *this_type;
@@ -580,7 +580,7 @@ python_xmethod_worker::invoke (struct value *obj,
     }
   else
     {
-      res = allocate_value (lookup_typename (python_language,
+      res = allocate_value (lookup_typename (current_language,
 					     "void", NULL, 0));
     }
 
diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index 583989c5a6d..4346d238fb0 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -625,14 +625,36 @@ class gdbpy_enter
 {
  public:
 
-  gdbpy_enter (struct gdbarch *gdbarch, const struct language_defn *language);
+  /* Set the ambient Python architecture to GDBARCH and the language
+     to LANGUAGE.  If GDBARCH is nullptr, then the architecture will
+     be computed, when needed, using get_current_arch; see the
+     gdb_gdbarch method.  If LANGUAGE is not nullptr, then the current
+     language at time of construction will be saved (to be restored on
+     destruction), and the current language will be set to
+     LANGUAGE.  */
+  explicit gdbpy_enter (struct gdbarch *gdbarch = nullptr,
+			const struct language_defn *language = nullptr);
 
   ~gdbpy_enter ();
 
   DISABLE_COPY_AND_ASSIGN (gdbpy_enter);
 
+  /* Return the current gdbarch, as known to the Python layer.  This
+     is either python_gdbarch (which comes from the most recent call
+     to the gdbpy_enter constructor), or, if that is nullptr, the
+     result of get_current_arch.  */
+  static struct gdbarch *get_gdbarch ();
+
+  /* Called only during gdb shutdown.  This sets python_gdbarch to an
+     acceptable value.  */
+  static void finalize ();
+
  private:
 
+  /* The current gdbarch, according to Python.  This can be
+     nullptr.  */
+  static struct gdbarch *python_gdbarch;
+
   struct active_ext_lang_state *m_previous_active;
   PyGILState_STATE m_state;
   struct gdbarch *m_gdbarch;
@@ -680,9 +702,6 @@ class gdbpy_allow_threads
   PyThreadState *m_save;
 };
 
-extern struct gdbarch *python_gdbarch;
-extern const struct language_defn *python_language;
-
 /* Use this after a TRY_EXCEPT to throw the appropriate Python
    exception.  */
 #define GDB_PY_HANDLE_EXCEPTION(Exception)	\
diff --git a/gdb/python/python.c b/gdb/python/python.c
index e05b99c0bec..d1b03aec328 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -192,13 +192,12 @@ const struct extension_language_defn extension_language_python =
 
 /* Architecture and language to be used in callbacks from
    the Python interpreter.  */
-struct gdbarch *python_gdbarch;
-const struct language_defn *python_language;
+struct gdbarch *gdbpy_enter::python_gdbarch;
 
 gdbpy_enter::gdbpy_enter  (struct gdbarch *gdbarch,
 			   const struct language_defn *language)
 : m_gdbarch (python_gdbarch),
-  m_language (python_language)
+  m_language (language == nullptr ? nullptr : current_language)
 {
   /* We should not ever enter Python unless initialized.  */
   if (!gdb_python_initialized)
@@ -209,7 +208,8 @@ gdbpy_enter::gdbpy_enter  (struct gdbarch *gdbarch,
   m_state = PyGILState_Ensure ();
 
   python_gdbarch = gdbarch;
-  python_language = language;
+  if (language != nullptr)
+    set_language (language->la_language);
 
   /* Save it and ensure ! PyErr_Occurred () afterwards.  */
   m_error.emplace ();
@@ -228,12 +228,27 @@ gdbpy_enter::~gdbpy_enter ()
   m_error->restore ();
 
   python_gdbarch = m_gdbarch;
-  python_language = m_language;
+  if (m_language != nullptr)
+    set_language (m_language->la_language);
 
   restore_active_ext_lang (m_previous_active);
   PyGILState_Release (m_state);
 }
 
+struct gdbarch *
+gdbpy_enter::get_gdbarch ()
+{
+  if (python_gdbarch != nullptr)
+    return python_gdbarch;
+  return get_current_arch ();
+}
+
+void
+gdbpy_enter::finalize ()
+{
+  python_gdbarch = target_gdbarch ();
+}
+
 /* A helper class to save and restore the GIL, but without touching
    the other globals that are handled by gdbpy_enter.  */
 
@@ -318,7 +333,7 @@ python_interactive_command (const char *arg, int from_tty)
 
   arg = skip_spaces (arg);
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   if (arg && *arg)
     {
@@ -412,7 +427,7 @@ gdbpy_eval_from_control_command (const struct extension_language_defn *extlang,
   if (cmd->body_list_1 != nullptr)
     error (_("Invalid \"python\" block structure."));
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   std::string script = compute_python_string (cmd->body_list_0.get ());
   ret = PyRun_SimpleString (script.c_str ());
@@ -425,7 +440,7 @@ gdbpy_eval_from_control_command (const struct extension_language_defn *extlang,
 static void
 python_command (const char *arg, int from_tty)
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   scoped_restore save_async = make_scoped_restore (&current_ui->async, 0);
 
@@ -556,7 +571,7 @@ gdbpy_parameter (PyObject *self, PyObject *args)
 static PyObject *
 gdbpy_target_charset (PyObject *self, PyObject *args)
 {
-  const char *cset = target_charset (python_gdbarch);
+  const char *cset = target_charset (gdbpy_enter::get_gdbarch ());
 
   return PyUnicode_Decode (cset, strlen (cset), host_charset (), NULL);
 }
@@ -566,7 +581,7 @@ gdbpy_target_charset (PyObject *self, PyObject *args)
 static PyObject *
 gdbpy_target_wide_charset (PyObject *self, PyObject *args)
 {
-  const char *cset = target_wide_charset (python_gdbarch);
+  const char *cset = target_wide_charset (gdbpy_enter::get_gdbarch ());
 
   return PyUnicode_Decode (cset, strlen (cset), host_charset (), NULL);
 }
@@ -857,7 +872,7 @@ gdbpy_decode_line (PyObject *self, PyObject *args)
     }
 
   if (arg != NULL)
-    location = string_to_event_location_basic (&arg, python_language,
+    location = string_to_event_location_basic (&arg, current_language,
 					       symbol_name_match_type::WILD);
 
   std::vector<symtab_and_line> decoded_sals;
@@ -962,7 +977,7 @@ static void
 gdbpy_source_script (const struct extension_language_defn *extlang,
 		     FILE *file, const char *filename)
 {
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
   python_run_simple_file (file, filename);
 }
 
@@ -1001,7 +1016,7 @@ struct gdbpy_event
 
   void operator() ()
   {
-    gdbpy_enter enter_py (get_current_arch (), current_language);
+    gdbpy_enter enter_py;
 
     gdbpy_ref<> call_result (PyObject_CallObject (m_func, NULL));
     if (call_result == NULL)
@@ -1050,7 +1065,7 @@ gdbpy_before_prompt_hook (const struct extension_language_defn *extlang,
   if (!gdb_python_initialized)
     return EXT_LANG_RC_NOP;
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   if (!evregpy_no_listeners_p (gdb_py_events.before_prompt)
       && evpy_emit_event (NULL, gdb_py_events.before_prompt) < 0)
@@ -1125,7 +1140,7 @@ gdbpy_colorize (const std::string &filename, const std::string &contents)
   if (!gdb_python_initialized)
     return {};
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   if (gdb_python_module == nullptr
       || !PyObject_HasAttrString (gdb_python_module, "colorize"))
@@ -1390,7 +1405,7 @@ gdbpy_source_objfile_script (const struct extension_language_defn *extlang,
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (objfile->arch (), current_language);
+  gdbpy_enter enter_py (objfile->arch ());
   scoped_restore restire_current_objfile
     = make_scoped_restore (&gdbpy_current_objfile, objfile);
 
@@ -1411,7 +1426,7 @@ gdbpy_execute_objfile_script (const struct extension_language_defn *extlang,
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (objfile->arch (), current_language);
+  gdbpy_enter enter_py (objfile->arch ());
   scoped_restore restire_current_objfile
     = make_scoped_restore (&gdbpy_current_objfile, objfile);
 
@@ -1443,7 +1458,7 @@ gdbpy_start_type_printers (const struct extension_language_defn *extlang,
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   gdbpy_ref<> type_module (PyImport_ImportModule ("gdb.types"));
   if (type_module == NULL)
@@ -1488,7 +1503,7 @@ gdbpy_apply_type_printers (const struct extension_language_defn *extlang,
   if (!gdb_python_initialized)
     return EXT_LANG_RC_NOP;
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   gdbpy_ref<> type_obj (type_to_type_object (type));
   if (type_obj == NULL)
@@ -1551,7 +1566,7 @@ gdbpy_free_type_printers (const struct extension_language_defn *extlang,
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
   Py_DECREF (printers);
 }
 
@@ -1686,8 +1701,7 @@ finalize_python (void *ignore)
   previous_active = set_active_ext_lang (&extension_language_python);
 
   (void) PyGILState_Ensure ();
-  python_gdbarch = target_gdbarch ();
-  python_language = current_language;
+  gdbpy_enter::finalize ();
 
   Py_Finalize ();
 
@@ -1746,7 +1760,7 @@ gdbpy_gdb_exiting (int exit_code)
   if (!gdb_python_initialized)
     return;
 
-  gdbpy_enter enter_py (python_gdbarch, python_language);
+  gdbpy_enter enter_py;
 
   if (emit_exiting_event (exit_code) < 0)
     gdbpy_print_stack ();
@@ -2164,7 +2178,7 @@ gdbpy_initialize (const struct extension_language_defn *extlang)
   if (!do_start_initialization () && PyErr_Occurred ())
     gdbpy_print_stack ();
 
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_enter enter_py;
 
   if (!do_initialize (extlang))
     {
diff --git a/gdb/testsuite/gdb.python/py-inferior.exp b/gdb/testsuite/gdb.python/py-inferior.exp
index 5b5f58243e4..aa78a1540cf 100644
--- a/gdb/testsuite/gdb.python/py-inferior.exp
+++ b/gdb/testsuite/gdb.python/py-inferior.exp
@@ -220,6 +220,7 @@ with_test_prefix "is_valid" {
     gdb_test "python print (inf_list\[0\].is_valid())" "True" \
 	"check inferior validity 1"
 
+    # The "dummy" line below used to cause a gdb crash.
     gdb_test_multiline "install new inferior event handler" \
 	"python" "" \
 	"my_inferior_count = 1" "" \
@@ -227,6 +228,7 @@ with_test_prefix "is_valid" {
 	"  global my_inferior_count" "" \
 	"  if evt.inferior is not None:" "" \
 	"    my_inferior_count = my_inferior_count + 1" "" \
+	"    dummy = gdb.Value(True)" "" \
 	"gdb.events.new_inferior.connect(new_inf_handler)" "" \
 	"end" ""
     gdb_test_multiline "install inferior deleted event handler" \
diff --git a/gdb/testsuite/gdb.python/py-lookup-type.exp b/gdb/testsuite/gdb.python/py-lookup-type.exp
index 52a1dae20ed..534a5fd418e 100644
--- a/gdb/testsuite/gdb.python/py-lookup-type.exp
+++ b/gdb/testsuite/gdb.python/py-lookup-type.exp
@@ -54,3 +54,11 @@ test_lookup_type "opencl" "ushort"
 test_lookup_type "objective-c" "char"
 
 test_lookup_type "pascal" "char"
+
+# Ensure that the language can be changed from within Python and still
+# affect the results.
+gdb_test_multiline "look up ada type from another language" \
+    "python" "" \
+    "gdb.execute('set language ada')" "" \
+    "print(gdb.lookup_type('character'))" "" \
+    "end" "character"
-- 
2.31.1

[PATCH v2 2/3] Fix another crash with gdb parameters in Python

[Tom Tromey]

While looking into the language-capturing issue, I found another way
to crash gdb using parameters from Python:

(gdb) python print(gdb.parameter('endian'))

(This is related to PR python/12188, though this patch isn't going to
fix what that bug is really about.)

The problem here is that the global variable that underlies the
"endian" parameter is initialized to NULL.  However, that's not a
valid value for an "enum" set/show parameter.

My understanding is that, in gdb, an "enum" parameter's underlying
variable must have a value that is "==" (not just strcmp-equal) to one
of the values coming from the enum array.  This invariant is relied on
in various places.

I started this patch by fixing the problem with "endian".  Then I
added some assertions to add_setshow_enum_cmd to try to catch other
problems of the same type.

This patch fixes all the problems that I found.  I also looked at all
the calls to add_setshow_enum_cmd to ensure that they were all
included in the gdb I tested.  I think they are: there are no calls in
nat-* files, or in remote-sim.c; and I was trying a build with all
targets, Python, and Guile enabled.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=12188
---
 gdb/arch-utils.c                          |  5 +++--
 gdb/arm-tdep.c                            |  2 ++
 gdb/charset.c                             |  9 +++++++++
 gdb/cli/cli-decode.c                      | 10 ++++++++++
 gdb/guile/scm-param.c                     |  4 ++--
 gdb/language.c                            | 11 ++++++-----
 gdb/osabi.c                               |  4 +++-
 gdb/python/py-param.c                     |  4 ++--
 gdb/testsuite/gdb.python/py-parameter.exp |  4 ++++
 9 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/gdb/arch-utils.c b/gdb/arch-utils.c
index 38e3132668d..3ee978a0249 100644
--- a/gdb/arch-utils.c
+++ b/gdb/arch-utils.c
@@ -359,7 +359,7 @@ static const char *const endian_enum[] =
   endian_auto,
   NULL,
 };
-static const char *set_endian_string;
+static const char *set_endian_string = endian_auto;
 
 enum bfd_endian
 selected_byte_order (void)
@@ -757,7 +757,8 @@ initialize_current_architecture (void)
      list of architectures.  */
   {
     /* Append ``auto''.  */
-    arches.push_back ("auto");
+    set_architecture_string = "auto";
+    arches.push_back (set_architecture_string);
     arches.push_back (nullptr);
     set_show_commands architecture_cmds
       = add_setshow_enum_cmd ("architecture", class_support,
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index f6bd76a354d..f46913e8eaa 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -9802,6 +9802,8 @@ _initialize_arm_tdep ()
 	size_t offset = strlen ("reg-names-");
 	const char *style = disasm_options->name[i];
 	valid_disassembly_styles[j++] = &style[offset];
+	if (strcmp (&style[offset], "std") == 0)
+	  disassembly_style = &style[offset];
 	length = snprintf (rdptr, rest, "%s - %s\n", &style[offset],
 			   disasm_options->description[i]);
 	rdptr += length;
diff --git a/gdb/charset.c b/gdb/charset.c
index 0b3ef26f1d6..e011793f746 100644
--- a/gdb/charset.c
+++ b/gdb/charset.c
@@ -1029,6 +1029,9 @@ _initialize_charset ()
 #endif
 #endif
 
+  /* Recall that the first element is always "auto".  */
+  host_charset_name = charset_enum[0];
+  gdb_assert (strcmp (host_charset_name, "auto") == 0);
   add_setshow_enum_cmd ("charset", class_support,
 			charset_enum, &host_charset_name, _("\
 Set the host and target character sets."), _("\
@@ -1057,6 +1060,9 @@ To see a list of the character sets GDB supports, type `set host-charset <TAB>'.
 			show_host_charset_name,
 			&setlist, &showlist);
 
+  /* Recall that the first element is always "auto".  */
+  target_charset_name = charset_enum[0];
+  gdb_assert (strcmp (target_charset_name, "auto") == 0);
   add_setshow_enum_cmd ("target-charset", class_support,
 			charset_enum, &target_charset_name, _("\
 Set the target character set."), _("\
@@ -1069,6 +1075,9 @@ To see a list of the character sets GDB supports, type `set target-charset'<TAB>
 			show_target_charset_name,
 			&setlist, &showlist);
 
+  /* Recall that the first element is always "auto".  */
+  target_wide_charset_name = charset_enum[0];
+  gdb_assert (strcmp (target_wide_charset_name, "auto") == 0);
   add_setshow_enum_cmd ("target-wide-charset", class_support,
 			charset_enum, &target_wide_charset_name,
 			_("\
diff --git a/gdb/cli/cli-decode.c b/gdb/cli/cli-decode.c
index 7266fb36d0d..bf6404a5755 100644
--- a/gdb/cli/cli-decode.c
+++ b/gdb/cli/cli-decode.c
@@ -613,6 +613,16 @@ add_setshow_enum_cmd (const char *name,
 		      struct cmd_list_element **set_list,
 		      struct cmd_list_element **show_list)
 {
+  /* We require *VAR to be initialized before this call, and
+     furthermore it must be == to one of the values in ENUMLIST.  */
+  gdb_assert (var != nullptr && *var != nullptr);
+  for (int i = 0; ; ++i)
+    {
+      gdb_assert (enumlist[i] != nullptr);
+      if (*var == enumlist[i])
+	break;
+    }
+
   set_show_commands commands
     =  add_setshow_cmd_full<const char *> (name, theclass, var_enum, var,
 					   set_doc, show_doc, help_doc,
diff --git a/gdb/guile/scm-param.c b/gdb/guile/scm-param.c
index 125b0e4766b..a3af3c2251e 100644
--- a/gdb/guile/scm-param.c
+++ b/gdb/guile/scm-param.c
@@ -458,12 +458,12 @@ add_setshow_generic (enum var_types param_type, enum command_class cmd_class,
       break;
 
     case var_enum:
+      /* Initialize the value, just in case.  */
+      make_setting (self).set<const char *> (self->enumeration[0]);
       commands = add_setshow_enum_cmd (cmd_name, cmd_class, self->enumeration,
 				       &self->value.cstringval, set_doc,
 				       show_doc, help_doc, set_func, show_func,
 				       set_list, show_list);
-      /* Initialize the value, just in case.  */
-      make_setting (self).set<const char *> (self->enumeration[0]);
       break;
 
     default:
diff --git a/gdb/language.c b/gdb/language.c
index 0846b3e5eeb..f000142fc2d 100644
--- a/gdb/language.c
+++ b/gdb/language.c
@@ -476,7 +476,8 @@ add_set_language_command ()
   /* Display "auto", "local" and "unknown" first, and then the rest,
      alpha sorted.  */
   const char **language_names_p = language_names;
-  *language_names_p++ = language_def (language_auto)->name ();
+  language = language_def (language_auto)->name ();
+  *language_names_p++ = language;
   *language_names_p++ = "local";
   *language_names_p++ = language_def (language_unknown)->name ();
   const char **sort_begin = language_names_p;
@@ -1150,6 +1151,8 @@ _initialize_language ()
   add_alias_cmd ("c", setshow_check_cmds.show, no_class, 1, &showlist);
   add_alias_cmd ("ch", setshow_check_cmds.show, no_class, 1, &showlist);
 
+  range = type_or_range_names[3];
+  gdb_assert (strcmp (range, "auto") == 0);
   add_setshow_enum_cmd ("range", class_support, type_or_range_names,
 			&range,
 			_("Set range checking (on/warn/off/auto)."),
@@ -1158,6 +1161,8 @@ _initialize_language ()
 			show_range_command,
 			&setchecklist, &showchecklist);
 
+  case_sensitive = case_sensitive_names[2];
+  gdb_assert (strcmp (case_sensitive, "auto") == 0);
   add_setshow_enum_cmd ("case-sensitive", class_support, case_sensitive_names,
 			&case_sensitive, _("\
 Set case sensitivity in name search (on/off/auto)."), _("\
@@ -1174,10 +1179,6 @@ For Fortran the default is off; for other languages the default is on."),
 
   add_set_language_command ();
 
-  language = "auto";
-  range = "auto";
-  case_sensitive = "auto";
-
   /* Have the above take effect.  */
   set_language (language_auto);
 }
diff --git a/gdb/osabi.c b/gdb/osabi.c
index 40c86e782e7..d4a98061dbd 100644
--- a/gdb/osabi.c
+++ b/gdb/osabi.c
@@ -666,11 +666,13 @@ _initialize_gdb_osabi ()
 				  generic_elf_osabi_sniffer);
 
   /* Register the "set osabi" command.  */
+  user_osabi_state = osabi_auto;
+  set_osabi_string = gdb_osabi_available_names[0];
+  gdb_assert (strcmp (set_osabi_string, "auto") == 0);
   add_setshow_enum_cmd ("osabi", class_support, gdb_osabi_available_names,
 			&set_osabi_string,
 			_("Set OS ABI of target."),
 			_("Show OS ABI of target."),
 			NULL, set_osabi, show_osabi,
 			&setlist, &showlist);
-  user_osabi_state = osabi_auto;
 }
diff --git a/gdb/python/py-param.c b/gdb/python/py-param.c
index 8559bc997ea..6ee14d42ab8 100644
--- a/gdb/python/py-param.c
+++ b/gdb/python/py-param.c
@@ -572,13 +572,13 @@ add_setshow_generic (int parmclass, enum command_class cmdclass,
       break;
 
     case var_enum:
+      /* Initialize the value, just in case.  */
+      self->value.cstringval = self->enumeration[0];
       commands = add_setshow_enum_cmd (cmd_name.get (), cmdclass,
 				       self->enumeration,
 				       &self->value.cstringval, set_doc,
 				       show_doc, help_doc, get_set_value,
 				       get_show_value, set_list, show_list);
-      /* Initialize the value, just in case.  */
-      self->value.cstringval = self->enumeration[0];
       break;
 
     default:
diff --git a/gdb/testsuite/gdb.python/py-parameter.exp b/gdb/testsuite/gdb.python/py-parameter.exp
index b025c2562f0..2de148c1b27 100644
--- a/gdb/testsuite/gdb.python/py-parameter.exp
+++ b/gdb/testsuite/gdb.python/py-parameter.exp
@@ -364,3 +364,7 @@ test_really_undocumented_parameter
 test_deprecated_api_parameter
 test_integer_parameter
 test_throwing_parameter
+
+# This caused a gdb crash.
+gdb_test "python print(gdb.parameter('endian'))" "auto" \
+    "print endian parameter"
-- 
2.31.1

[PATCH v2 3/3] Add a way to temporarily set a gdb parameter from Python

[Tom Tromey]

It's sometimes useful to temporarily set some gdb parameter from
Python.  Now that the 'endian' crash is fixed, and now that the
current language is no longer captured by the Python layer, it seems
reasonable to add a helper function for this situation.

This adds a new gdb.with_parameter function.  This creates a context
manager which temporarily sets some parameter to a specified value.
The old value is restored when the context is exited.  This is most
useful with the Python "with" statement:

   with gdb.with_parameter('language', 'ada'):
      ... do Ada stuff

This also adds a simple function to set a parameter,
gdb.set_parameter, as suggested by Andrew.

This is PR python/10790.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=10790
---
 gdb/NEWS                                    |  7 ++++++
 gdb/doc/python.texi                         | 26 +++++++++++++++++++++
 gdb/python/lib/gdb/__init__.py              | 17 ++++++++++++++
 gdb/testsuite/gdb.python/py-lookup-type.exp | 18 ++++++++++++++
 4 files changed, 68 insertions(+)

diff --git a/gdb/NEWS b/gdb/NEWS
index c26e15b530a..c3c73b4e004 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -120,6 +120,13 @@ clone-inferior
      is equivalent to the existing 'maint packet' CLI command; it
      allows a user specified packet to be sent to the remote target.
 
+  ** New gdb.set_parameter(NAME, VALUE).  This sets the gdb parameter
+     NAME to VALUE.
+
+  ** New gdb.with_parameter(NAME, VALUE).  This returns a context
+     manager that temporarily sets the gdb parameter NAME to VALUE,
+     then resets it when the context is exited.
+
 * New features in the GDB remote stub, GDBserver
 
   ** GDBserver is now supported on OpenRISC GNU/Linux.
diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index 6bd5f6b90ac..2f309d7d91b 100644
--- a/gdb/doc/python.texi
+++ b/gdb/doc/python.texi
@@ -332,6 +332,32 @@ parameter's value is converted to a Python value of the appropriate
 type, and returned.
 @end defun
 
+@findex gdb.set_parameter
+@defun gdb.set_parameter (name, value)
+Sets the gdb parameter @var{name} to @var{value}.  As with
+@code{gdb.parameter}, the parameter name string may contain spaces if
+the parameter has a multi-part name.
+@end defun
+
+@findex gdb.with_parameter
+@defun gdb.with_parameter (name, value)
+Create a Python context manager (for use with the Python
+@command{with} statement) that temporarily sets the gdb parameter
+@var{name} to @var{value}.  On exit from the context, the previous
+value will be restored.
+
+This uses @code{gdb.parameter} in its implementation, so it can throw
+the same exceptions as that function.
+
+For example, it's sometimes useful to evaluate some Python code with a
+particular gdb language:
+
+@smallexample
+with gdb.with_parameter('language', 'pascal'):
+  ... language-specific operations
+@end smallexample
+@end defun
+
 @findex gdb.history
 @defun gdb.history (number)
 Return a value from @value{GDBN}'s value history (@pxref{Value
diff --git a/gdb/python/lib/gdb/__init__.py b/gdb/python/lib/gdb/__init__.py
index 11a1b444bfd..b32c66f6cb4 100644
--- a/gdb/python/lib/gdb/__init__.py
+++ b/gdb/python/lib/gdb/__init__.py
@@ -17,6 +17,7 @@ import traceback
 import os
 import sys
 import _gdb
+from contextlib import contextmanager
 
 # Python 3 moved "reload"
 if sys.version_info >= (3, 4):
@@ -231,6 +232,22 @@ def find_pc_line(pc):
     return current_progspace().find_pc_line(pc)
 
 
+def set_parameter(name, value):
+    """Set the GDB parameter NAME to VALUE."""
+    execute('set ' + name + ' ' + str(value), to_string=True)
+
+
+@contextmanager
+def with_parameter(name, value):
+    """Temporarily set the GDB parameter NAME to VALUE.
+    Note that this is a context manager."""
+    old_value = parameter(name)
+    set_parameter(name, value)
+    # Nothing that useful to return.
+    yield None
+    set_parameter(name, old_value)
+
+
 try:
     from pygments import formatters, lexers, highlight
 
diff --git a/gdb/testsuite/gdb.python/py-lookup-type.exp b/gdb/testsuite/gdb.python/py-lookup-type.exp
index 534a5fd418e..596ab9a9af8 100644
--- a/gdb/testsuite/gdb.python/py-lookup-type.exp
+++ b/gdb/testsuite/gdb.python/py-lookup-type.exp
@@ -55,6 +55,19 @@ test_lookup_type "objective-c" "char"
 
 test_lookup_type "pascal" "char"
 
+gdb_test "show language" \
+    "The current source language is .pascal.." \
+    "show language before 'with'"
+gdb_test_multiline "look up type using set_parameter" \
+    "python" "" \
+    "with gdb.with_parameter('language', 'ada'):" "" \
+    "  print(gdb.lookup_type('character'))" "" \
+    "end" "character"
+gdb_test "show language" \
+    "The current source language is .pascal.." \
+    "show language after 'with'"
+
+
 # Ensure that the language can be changed from within Python and still
 # affect the results.
 gdb_test_multiline "look up ada type from another language" \
@@ -62,3 +75,8 @@ gdb_test_multiline "look up ada type from another language" \
     "gdb.execute('set language ada')" "" \
     "print(gdb.lookup_type('character'))" "" \
     "end" "character"
+
+gdb_test_no_output "python gdb.set_parameter('language', 'rust')"
+gdb_test "show language" \
+    "The current source language is .rust.." \
+    "show language after 'set_parameter'"
-- 
2.31.1

Re: [PATCH v2 3/3] Add a way to temporarily set a gdb parameter from Python

[Lancelot SIX]

> +
> +
> +@contextmanager
> +def with_parameter(name, value):
> +    """Temporarily set the GDB parameter NAME to VALUE.
> +    Note that this is a context manager."""
> +    old_value = parameter(name)
> +    set_parameter(name, value)
> +    # Nothing that useful to return.
> +    yield None
> +    set_parameter(name, old_value)
> +
> +

Hi,

In python, context managers are usually used the way RAII resources are
in c++. which is to ensure some resource is reliably released (parameter
is restored in this case) at the end of the block.  Here, if an
exception is thrown within the block, the original value is not
restored.

I would suggest something like:


    @contextmanager
    def with_parameter(name, value):
        """Temporarily set the GDB parameter NAME to VALUE.
        Note that this is a context manager."""
        old_value = parameter(name)
        set_parameter(name, value)
        try:
            yield
        finally:
            set_parameter(name, old_value)


This way, the parameter is restored even in case of exception, which is
what I would expect from a python user point of view.

Best,
Lancelot.

Re: [PATCH v2 3/3] Add a way to temporarily set a gdb parameter from Python

[Tom Tromey]

Lancelot>         try:
Lancelot>             yield
Lancelot>         finally:
Lancelot>             set_parameter(name, old_value)

Lancelot> This way, the parameter is restored even in case of exception, which is
Lancelot> what I would expect from a python user point of view.

Yeah, thanks.  I had assumed @contextmanager would handle this.
Anyway I'll make this change.

Tom

Re: [PATCH v2 0/3] Improvements to Python parameters

[Tom Tromey]

>>>>> "Tom" == Tom Tromey via Gdb-patches <gdb-patches@sourceware.org> writes:

Tom> Here's v2 of the series to improve Python parameters in a few ways.
Tom> v1 is here:

Tom>     https://sourceware.org/pipermail/gdb-patches/2022-January/184826.html

Tom> I think this fixes all the review comments.

I'm checking this in now.

Tom

Re: [PATCH v2 1/3] Change how Python architecture and language are handled

[Simon Marchi]

On 2022-01-10 16:51, Tom Tromey via Gdb-patches wrote:
> Currently, gdb's Python layer captures the current architecture and
> language when "entering" Python code.  This has some undesirable
> effects, and so this series changes how this is handled.
> 
> First, there is code like this:
> 
>   gdbpy_enter enter_py (python_gdbarch, python_language);
> 
> This is incorrect, because both of these are NULL when not otherwise
> assigned.  This can cause crashes in some cases -- I've added one to
> the test suite.  (Note that this crasher is just an example, other
> ones along the same lines are possible.)
> 
> Second, when the language is captured in this way, it means that
> Python code cannot affect the current language for its own purposes.
> It's reasonable to want to write code like this:
> 
>     gdb.execute('set language mumble')
>     ... stuff using the current language
>     gdb.execute('set language previous-value')
> 
> However, this won't actually work, because the language is captured on
> entry.  I've added a test to show this as well.
> 
> This patch changes gdb to try to avoid capturing the current values.
> The Python concept of the current gdbarch is only set in those few
> cases where a non-default value is computed or needed; and the
> language is not captured at all -- instead, in the cases where it's
> required, the current language is temporarily changed.

Hi Tom,

Starting with this patch, I get this failure, consistently:

 78 (gdb) print pid^M
 79 $1 = 1915550^M
 80 (gdb) PASS: gdb.threads/killed-outside.exp: get pid of inferior
 81 Executing on target: kill -9 1915550    (timeout = 300)
 82 builtin_spawn -ignore SIGHUP kill -9 1915550^M
 83 continue^M
 84 Continuing.^M
 85 Couldn't get registers: No such process.^M
 86 (gdb) FAIL: gdb.threads/killed-outside.exp: prompt after first continue

Do you see it?

Simon