Fix crash in gdbpy_parse_register_id

I noticed that gdbpy_parse_register_id would assert if passed a Python
object of a type it was not expecting.  The included test case shows
this crash.  This patch fixes the problem and also changes
gdbpy_parse_register_id to be more "Python-like" -- it always ensures
the Python error is set when it fails, and the callers now simply
propagate the existing exception.

gdb/python/py-frame.c

@@ -253,10 +253,7 @@ frapy_read_register (PyObject *self, PyObject *args)
 
       if (!gdbpy_parse_register_id (get_frame_arch (frame), pyo_reg_id,
 				    &regnum))
-	{
-	  PyErr_SetString (PyExc_ValueError, "Bad register");
-	  return NULL;
-	}
+	return nullptr;
 
       gdb_assert (regnum >= 0);
       val = value_of_register (regnum, frame);

gdb/python/py-registers.c

@@ -381,21 +381,27 @@ gdbpy_parse_register_id (struct gdbarch *gdbarch, PyObject *pyo_reg_id,
 	{
 	  *reg_num = user_reg_map_name_to_regnum (gdbarch, reg_name.get (),
 						  strlen (reg_name.get ()));
-	  return *reg_num >= 0;
+	  if (*reg_num >= 0)
+	    return true;
+	  PyErr_SetString (PyExc_ValueError, "Bad register");
 	}
     }
   /* The register could be its internal GDB register number.  */
   else if (PyLong_Check (pyo_reg_id))
     {
       long value;
-      if (gdb_py_int_as_long (pyo_reg_id, &value) && (int) value == value)
+      if (gdb_py_int_as_long (pyo_reg_id, &value) == 0)
 	{
-	  if (user_reg_map_regnum_to_name (gdbarch, value) != NULL)
+	  /* Nothing -- error.  */
+	}
+      else if ((int) value == value
+	       && user_reg_map_regnum_to_name (gdbarch, value) != NULL)
 	{
 	  *reg_num = (int) value;
 	  return true;
 	}
-	}
+      else
+	PyErr_SetString (PyExc_ValueError, "Bad register");
     }
   /* The register could be a gdb.RegisterDescriptor object.  */
   else if (PyObject_IsInstance (pyo_reg_id,
@@ -412,6 +418,8 @@ gdbpy_parse_register_id (struct gdbarch *gdbarch, PyObject *pyo_reg_id,
 	PyErr_SetString (PyExc_ValueError,
 			 _("Invalid Architecture in RegisterDescriptor"));
     }
+  else
+    PyErr_SetString (PyExc_TypeError, _("Invalid type for register"));
 
   gdb_assert (PyErr_Occurred ());
   return false;

gdb/python/py-unwind.c

@@ -260,10 +260,7 @@ unwind_infopy_add_saved_register (PyObject *self, PyObject *args)
 			  &pyo_reg_id, &pyo_reg_value))
     return NULL;
   if (!gdbpy_parse_register_id (pending_frame->gdbarch, pyo_reg_id, &regnum))
-    {
-      PyErr_SetString (PyExc_ValueError, "Bad register");
-      return NULL;
-    }
+    return nullptr;
 
   /* If REGNUM identifies a user register then *maybe* we can convert this
      to a real (i.e. non-user) register.  The maybe qualifier is because we
@@ -381,10 +378,7 @@ pending_framepy_read_register (PyObject *self, PyObject *args)
   if (!PyArg_UnpackTuple (args, "read_register", 1, 1, &pyo_reg_id))
     return NULL;
   if (!gdbpy_parse_register_id (pending_frame->gdbarch, pyo_reg_id, &regnum))
-    {
-      PyErr_SetString (PyExc_ValueError, "Bad register");
-      return NULL;
-    }
+    return nullptr;
 
   try
     {

gdb/python/python-internal.h

@@ -819,7 +819,8 @@ typedef std::unique_ptr<Py_buffer, Py_buffer_deleter> Py_buffer_up;
 
    If a register is parsed successfully then *REG_NUM will have been
    updated, and true is returned.  Otherwise the contents of *REG_NUM are
-   undefined, and false is returned.
+   undefined, and false is returned.  When false is returned, the
+   Python error is set.
 
    The PYO_REG_ID object can be a string, the name of the register.  This
    is the slowest approach as GDB has to map the name to a number for each

gdb/testsuite/gdb.python/py-frame.exp

@@ -134,3 +134,9 @@ gdb_test "python print(gdb.selected_frame().language())" "c"
 gdb_test "set language ada"
 gdb_test "python print(gdb.selected_frame().language())" "c" \
     "frame language is not affected by global language"
+
+# This previously caused a crash -- the implementation was missing the
+# case where a register had an unexpected type.
+gdb_test "python print(gdb.selected_frame().read_register(list()))" \
+    ".*Invalid type for register.*" \
+    "test Frame.read_register with list"

gdb/testsuite/gdb.python/py-unwind.exp

@@ -57,3 +57,9 @@ gdb_test_sequence "where"  "Backtrace restored by unwinder" {
 
 # Check that the Python unwinder frames can be flushed / released.
 gdb_test "maint flush register-cache" "Register cache flushed\\." "flush frames"
+
+# Check that invalid register names cause errors.
+gdb_test "python print(add_saved_register_error)" "True" \
+    "add_saved_register error"
+gdb_test "python print(read_register_error)" "True" \
+    "read_register error"

gdb/testsuite/gdb.python/py-unwind.py

@@ -17,6 +17,11 @@ import gdb
 from gdb.unwinder import Unwinder
 
 
+# These are set to test whether invalid register names cause an error.
+add_saved_register_error = False
+read_register_error = False
+
+
 class FrameId(object):
     def __init__(self, sp, pc):
         self._sp = sp
@@ -101,6 +106,12 @@ class TestUnwinder(Unwinder):
             previous_ip = self._read_word(bp + 8)
             previous_sp = bp + 16
 
+            try:
+                pending_frame.read_register("nosuchregister")
+            except ValueError:
+                global read_register_error
+                read_register_error = True
+
             frame_id = FrameId(
                 pending_frame.read_register(TestUnwinder.AMD64_RSP),
                 pending_frame.read_register(TestUnwinder.AMD64_RIP),
@@ -109,6 +120,11 @@ class TestUnwinder(Unwinder):
             unwind_info.add_saved_register(TestUnwinder.AMD64_RBP, previous_bp)
             unwind_info.add_saved_register("rip", previous_ip)
             unwind_info.add_saved_register("rsp", previous_sp)
+            try:
+                unwind_info.add_saved_register("nosuchregister", previous_sp)
+            except ValueError:
+                global add_saved_register_error
+                add_saved_register_error = True
             return unwind_info
         except (gdb.error, RuntimeError):
             return None