Change how Python architecture and language are handled

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.

1 files changed, 13 insertions, 14 deletions

diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index 45e33f9..46f0c9f 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;