merge

Cython/CodeWriter.py

@@ -26,12 +26,12 @@ class LinesResult(object):
         self.put(s)
         self.newline()
 
-class CodeWriter(TreeVisitor):
+class DeclarationWriter(TreeVisitor):
 
     indent_string = u"    "
 
     def __init__(self, result = None):
-        super(CodeWriter, self).__init__()
+        super(DeclarationWriter, self).__init__()
         if result is None:
             result = LinesResult()
         self.result = result
@@ -41,6 +41,7 @@ class CodeWriter(TreeVisitor):
 
     def write(self, tree):
         self.visit(tree)
+        return self.result
 
     def indent(self):
         self.numindents += 1
@@ -54,6 +55,9 @@ class CodeWriter(TreeVisitor):
     def put(self, s):
         self.result.put(s)
 
+    def putline(self, s):
+        self.result.putline(self.indent_string * self.numindents + s)
+
     def endline(self, s = u""):
         self.result.putline(s)
 
@@ -80,22 +84,44 @@ class CodeWriter(TreeVisitor):
     def visit_StatListNode(self, node):
         self.visitchildren(node)
     
-    def visit_FuncDefNode(self, node):
-        self.startline(u"def %s(" % node.name)
-        self.comma_separated_list(node.args)
-        self.endline(u"):")
+    def visit_CDefExternNode(self, node):
+        if node.include_file is None:
+            file = u'*'
+        else:
+            file = u'"%s"' % node.include_file
+        self.putline(u"cdef extern from %s:" % file)
         self.indent()
         self.visit(node.body)
         self.dedent()
 
-    def visit_CArgDeclNode(self, node):
-        if node.base_type.name is not None:
-            self.visit(node.base_type)
-            self.put(u" ")
-        self.visit(node.declarator)
-        if node.default is not None:
-            self.put(u" = ")
-            self.visit(node.default)
+    def visit_CPtrDeclaratorNode(self, node):
+        self.put('*')
+        self.visit(node.base)
+
+    def visit_CReferenceDeclaratorNode(self, node):
+        self.put('&')
+        self.visit(node.base)
+
+    def visit_CArrayDeclaratorNode(self, node):
+        self.visit(node.base)
+        self.put(u'[')
+        if node.dimension is not None:
+            self.visit(node.dimension)
+        self.put(u']')
+
+    def visit_CArrayDeclaratorNode(self, node):
+        self.visit(node.base)
+        self.put(u'[')
+        if node.dimension is not None:
+            self.visit(node.dimension)
+        self.put(u']')
+
+    def visit_CFuncDeclaratorNode(self, node):
+        # TODO: except, gil, etc.
+        self.visit(node.base)
+        self.put(u'(')
+        self.comma_separated_list(node.args)
+        self.endline(u')')
 
     def visit_CNameDeclaratorNode(self, node):
         self.put(node.name)
@@ -108,22 +134,149 @@ class CodeWriter(TreeVisitor):
                 self.put("short " * -node.longness)
             elif node.longness > 0:
                 self.put("long " * node.longness)
+        self.put(node.name)
+
+    def visit_CComplexBaseTypeNode(self, node):
+        self.put(u'(')
+        self.visit(node.base_type)
+        self.visit(node.declarator)
+        self.put(u')')
 
+    def visit_CNestedBaseTypeNode(self, node):
+        self.visit(node.base_type)
+        self.put(u'.')
         self.put(node.name)
 
-    def visit_SingleAssignmentNode(self, node):
-        self.startline()
-        self.visit(node.lhs)
+    def visit_TemplatedTypeNode(self, node):
+        self.visit(node.base_type_node)
+        self.put(u'[')
+        self.comma_separated_list(node.positional_args + node.keyword_args.key_value_pairs)
+        self.put(u']')
+
+    def visit_CVarDefNode(self, node):
+        self.startline(u"cdef ")
+        self.visit(node.base_type)
+        self.put(u" ")
+        self.comma_separated_list(node.declarators, output_rhs=True)
+        self.endline()
+
+    def visit_container_node(self, node, decl, extras, attributes):
+        # TODO: visibility
+        self.startline(decl)
+        if node.name:
+            self.put(u' ')
+            self.put(node.name)
+            if node.cname is not None:
+                self.put(u' "%s"' % node.cname)
+        if extras:
+            self.put(extras)
+        self.endline(':')
+        self.indent()
+        if not attributes:
+            self.putline('pass')
+        else:
+            for attribute in attributes:
+                self.visit(attribute)
+        self.dedent()
+
+    def visit_CStructOrUnionDefNode(self, node):
+        if node.typedef_flag:
+            decl = u'ctypedef '
+        else:
+            decl = u'cdef '
+        if node.visibility == 'public':
+            decl += u'public '
+        if node.packed:
+            decl += u'packed '
+        decl += node.kind
+        self.visit_container_node(node, decl, None, node.attributes)
+
+    def visit_CppClassNode(self, node):
+        extras = ""
+        if node.templates:
+            extras = u"[%s]" % ", ".join(node.templates)
+        if node.base_classes:
+            extras += "(%s)" % ", ".join(node.base_classes)
+        self.visit_container_node(node, u"cdef cppclass", extras, node.attributes)
+
+    def visit_CEnumDefNode(self, node):
+        self.visit_container_node(node, u"cdef enum", None, node.items)
+
+    def visit_CEnumDefItemNode(self, node):
+        self.startline(node.name)
+        if node.cname:
+            self.put(u' "%s"' % node.cname)
+        if node.value:
             self.put(u" = ")
-        self.visit(node.rhs)
+            self.visit(node.value)
         self.endline()
 
-    def visit_CascadedAssignmentNode(self, node):
-        self.startline()
-        for lhs in node.lhs_list:
-            self.visit(lhs)
+    def visit_CClassDefNode(self, node):
+        assert not node.module_name
+        if node.decorators:
+            for decorator in node.decorators:
+                self.visit(decorator)
+        self.startline(u"cdef class ")
+        self.put(node.class_name)
+        if node.base_class_name:
+            self.put(u"(")
+            if node.base_class_module:
+                self.put(node.base_class_module)
+                self.put(u".")
+            self.put(node.base_class_name)
+            self.put(u")")
+        self.endline(u":")
+        self.indent()
+        self.visit(node.body)
+        self.dedent()
+
+    def visit_CTypeDefNode(self, node):
+        self.startline(u"ctypedef ")
+        self.visit(node.base_type)
+        self.put(u" ")
+        self.visit(node.declarator)
+        self.endline()
+
+    def visit_FuncDefNode(self, node):
+        self.startline(u"def %s(" % node.name)
+        self.comma_separated_list(node.args)
+        self.endline(u"):")
+        self.indent()
+        self.visit(node.body)
+        self.dedent()
+
+    def visit_CArgDeclNode(self, node):
+        if node.base_type.name is not None:
+            self.visit(node.base_type)
+            self.put(u" ")
+        self.visit(node.declarator)
+        if node.default is not None:
             self.put(u" = ")
-        self.visit(node.rhs)
+            self.visit(node.default)
+
+    def visit_CImportStatNode(self, node):
+        self.startline(u"cimport ")
+        self.put(node.module_name)
+        if node.as_name:
+            self.put(u" as ")
+            self.put(node.as_name)
+        self.endline()
+
+    def visit_FromCImportStatNode(self, node):
+        self.startline(u"from ")
+        self.put(node.module_name)
+        self.put(u" cimport ")
+        first = True
+        for pos, name, as_name, kind in node.imported_names:
+            assert kind is None
+            if first:
+                first = False
+            else:
+                self.put(u", ")
+            self.put(name)
+            if as_name:
+                self.put(u" as ")
+                self.put(as_name)
         self.endline()
 
     def visit_NameNode(self, node):
@@ -132,6 +285,31 @@ class CodeWriter(TreeVisitor):
     def visit_IntNode(self, node):
         self.put(node.value)
 
+    def visit_NoneNode(self, node):
+        self.put(u"None")
+
+    def visit_NotNode(self, node):
+        self.put(u"(not ")
+        self.visit(node.operand)
+        self.put(u")")
+
+    def visit_DecoratorNode(self, node):
+        self.startline("@")
+        self.visit(node.decorator)
+        self.endline()
+
+    def visit_BinopNode(self, node):
+        self.visit(node.operand1)
+        self.put(u" %s " % node.operator)
+        self.visit(node.operand2)
+
+    def visit_AttributeNode(self, node):
+        self.visit(node.obj)
+        self.put(u".%s" % node.attribute)
+
+    def visit_BoolNode(self, node):
+        self.put(str(node.value))
+
     # FIXME: represent string nodes correctly
     def visit_StringNode(self, node):
         value = node.value
@@ -139,32 +317,27 @@ class CodeWriter(TreeVisitor):
             value = value.encode(value.encoding)
         self.put(repr(value))
 
-    def visit_IfStatNode(self, node):
-        # The IfClauseNode is handled directly without a seperate match
-        # for clariy.
-        self.startline(u"if ")
-        self.visit(node.if_clauses[0].condition)
-        self.endline(":")
-        self.indent()
-        self.visit(node.if_clauses[0].body)
-        self.dedent()
-        for clause in node.if_clauses[1:]:
-            self.startline("elif ")
-            self.visit(clause.condition)
-            self.endline(":")
-            self.indent()
-            self.visit(clause.body)
-            self.dedent()
-        if node.else_clause is not None:
-            self.line("else:")
-            self.indent()
-            self.visit(node.else_clause)
-            self.dedent()
-
     def visit_PassStatNode(self, node):
         self.startline(u"pass")
         self.endline()
 
+class CodeWriter(DeclarationWriter):
+
+    def visit_SingleAssignmentNode(self, node):
+        self.startline()
+        self.visit(node.lhs)
+        self.put(u" = ")
+        self.visit(node.rhs)
+        self.endline()
+
+    def visit_CascadedAssignmentNode(self, node):
+        self.startline()
+        for lhs in node.lhs_list:
+            self.visit(lhs)
+            self.put(u" = ")
+        self.visit(node.rhs)
+        self.endline()
+
     def visit_PrintStatNode(self, node):
         self.startline(u"print ")
         self.comma_separated_list(node.arg_tuple.args)
@@ -172,18 +345,6 @@ class CodeWriter(TreeVisitor):
             self.put(u",")
         self.endline()
 
-    def visit_BinopNode(self, node):
-        self.visit(node.operand1)
-        self.put(u" %s " % node.operator)
-        self.visit(node.operand2)
-
-    def visit_CVarDefNode(self, node):
-        self.startline(u"cdef ")
-        self.visit(node.base_type)
-        self.put(u" ")
-        self.comma_separated_list(node.declarators, output_rhs=True)
-        self.endline()
-
     def visit_ForInStatNode(self, node):
         self.startline(u"for ")
         self.visit(node.target)
@@ -199,6 +360,28 @@ class CodeWriter(TreeVisitor):
             self.visit(node.else_clause)
             self.dedent()
 
+    def visit_IfStatNode(self, node):
+        # The IfClauseNode is handled directly without a seperate match
+        # for clariy.
+        self.startline(u"if ")
+        self.visit(node.if_clauses[0].condition)
+        self.endline(":")
+        self.indent()
+        self.visit(node.if_clauses[0].body)
+        self.dedent()
+        for clause in node.if_clauses[1:]:
+            self.startline("elif ")
+            self.visit(clause.condition)
+            self.endline(":")
+            self.indent()
+            self.visit(clause.body)
+            self.dedent()
+        if node.else_clause is not None:
+            self.line("else:")
+            self.indent()
+            self.visit(node.else_clause)
+            self.dedent()
+
     def visit_SequenceNode(self, node):
         self.comma_separated_list(node.args) # Might need to discover whether we need () around tuples...hmm...
 
@@ -244,13 +427,6 @@ class CodeWriter(TreeVisitor):
         self.visit(node.body)
         self.dedent()
 
-    def visit_AttributeNode(self, node):
-        self.visit(node.obj)
-        self.put(u".%s" % node.attribute)
-
-    def visit_BoolNode(self, node):
-        self.put(str(node.value))
-
     def visit_TryFinallyStatNode(self, node):
         self.line(u"try:")
         self.indent()
@@ -289,25 +465,12 @@ class CodeWriter(TreeVisitor):
         self.visit(node.value)
         self.endline()
 
-    def visit_DecoratorNode(self, node):
-        self.startline("@")
-        self.visit(node.decorator)
-        self.endline()
-
     def visit_ReraiseStatNode(self, node):
         self.line("raise")
 
-    def visit_NoneNode(self, node):
-        self.put(u"None")
-
     def visit_ImportNode(self, node):
         self.put(u"(import %s)" % node.module_name.value)
 
-    def visit_NotNode(self, node):
-        self.put(u"(not ")
-        self.visit(node.operand)
-        self.put(u")")
-
     def visit_TempsBlockNode(self, node):
         """
         Temporaries are output like $1_1', where the first number is
@@ -323,3 +486,28 @@ class CodeWriter(TreeVisitor):
 
     def visit_TempRefNode(self, node):
         self.put(self.tempnames[node.handle])
+
+
+class PxdWriter(DeclarationWriter):
+    def __call__(self, node):
+        print u'\n'.join(self.write(node).lines)
+        return node
+
+    def visit_CFuncDefNode(self, node):
+        if 'inline' in node.modifiers:
+            return
+        if node.overridable:
+            self.startline(u'cpdef ')
+        else:
+            self.startline(u'cdef ')
+        if node.visibility != 'private':
+            self.put(node.visibility)
+            self.put(u' ')
+        if node.api:
+            self.put(u'api ')
+        self.visit(node.declarator)
+    
+    def visit_StatNode(self, node):
+        pass
+
+    
\ No newline at end of file

Cython/Compiler/ParseTreeTransforms.py

@@ -64,7 +64,6 @@ class SkipDeclarations(object):
     def visit_CStructOrUnionDefNode(self, node):
         return node
 
-
 class NormalizeTree(CythonTransform):
     """
     This transform fixes up a few things after parsing

Cython/Debugger/Tests/test_libcython_in_gdb.py

@@ -378,6 +378,32 @@ class TestExec(DebugTestCase):
         gdb.execute('cy exec some_random_var = 14')
         self.assertEqual('14', self.eval_command('some_random_var'))
 
+
+class CySet(DebugTestCase):
+
+    def test_cyset(self):
+        self.break_and_run('os.path.join("foo", "bar")')
+
+        gdb.execute('cy set a = $cy_eval("{None: []}")')
+        stringvalue = self.read_var("a", cast_to=str)
+        self.assertEqual(stringvalue, "{None: []}")
+
+
+class TestCyEval(DebugTestCase):
+    "Test the $cy_eval() gdb function."
+
+    def test_cy_eval(self):
+        # This function leaks a few objects in the GDB python process. This
+        # is no biggie
+        self.break_and_run('os.path.join("foo", "bar")')
+
+        result = gdb.execute('print $cy_eval("None")', to_string=True)
+        assert re.match(r'\$\d+ = None\n', result), result
+
+        result = gdb.execute('print $cy_eval("[a]")', to_string=True)
+        assert re.match(r'\$\d+ = \[0\]', result), result
+
+
 class TestClosure(DebugTestCase):
 
     def break_and_run_func(self, funcname):

Cython/Debugger/Tests/test_libpython_in_gdb.py

@@ -113,5 +113,3 @@ class TestPrettyPrinters(test_libcython_in_gdb.DebugTestCase):
         frame = self.pyobject_fromcode('PyEval_GetFrame()')
 
         self.assertEqual(type(frame), libpython.PyFrameObjectPtr)
\ No newline at end of file
-
-

Cython/Debugger/libcython.py

@@ -592,6 +592,7 @@ class CyCy(CythonCommand):
         cy bt / cy backtrace
         cy list
         cy print
+        cy set
         cy locals
         cy globals
         cy exec
@@ -607,6 +608,7 @@ class CyCy(CythonCommand):
                                             completer_class, prefix=True)
 
         commands = dict(
+            # GDB commands
             import_ = CyImport.register(),
             break_ = CyBreak.register(),
             step = CyStep.register(),
@@ -624,9 +626,13 @@ class CyCy(CythonCommand):
             globals = CyGlobals.register(),
             exec_ = libpython.FixGdbCommand('cy exec', '-cy-exec'),
             _exec = CyExec.register(),
+            set = CySet.register(),
+
+            # GDB functions
             cy_cname = CyCName('cy_cname'),
             cy_cvalue = CyCValue('cy_cvalue'),
             cy_lineno = CyLine('cy_lineno'),
+            cy_eval = CyEval('cy_eval'),
         )
 
         for command_name, command in commands.iteritems():
@@ -1169,15 +1175,14 @@ class CyGlobals(CyLocals):
                                              max_name_length, '    ')
 
 
-class CyExec(CythonCommand, libpython.PyExec):
+
+class EvaluateOrExecuteCodeMixin(object):
     """
-    Execute Python code in the nearest Python or Cython frame.
+    Evaluate or execute Python code in a Cython or Python frame. The 'evalcode'
+    method evaluations Python code, prints a traceback if an exception went
+    uncaught, and returns any return value as a gdb.Value (NULL on exception).
     """
 
-    name = '-cy-exec'
-    command_class = gdb.COMMAND_STACK
-    completer_class = gdb.COMPLETE_NONE
-
     def _fill_locals_dict(self, executor, local_dict_pointer):
         "Fill a remotely allocated dict with values from the Cython C stack"
         cython_func = self.get_cython_function()
@@ -1208,28 +1213,22 @@ class CyExec(CythonCommand, libpython.PyExec):
                         raise gdb.GdbError("Unable to execute Python code.")
                 finally:
                     # PyDict_SetItem doesn't steal our reference
-                    executor.decref(pystringp)
+                    executor.xdecref(pystringp)
 
     def _find_first_cython_or_python_frame(self):
         frame = gdb.selected_frame()
         while frame:
             if (self.is_cython_function(frame) or
                 self.is_python_function(frame)):
+                frame.select()
                 return frame
 
             frame = frame.older()
 
         raise gdb.GdbError("There is no Cython or Python frame on the stack.")
 
-    def invoke(self, expr, from_tty):
-        frame = self._find_first_cython_or_python_frame()
-        if self.is_python_function(frame):
-            libpython.py_exec.invoke(expr, from_tty)
-            return
-
-        expr, input_type = self.readcode(expr)
-        executor = libpython.PythonCodeExecutor()
 
+    def _evalcode_cython(self, executor, code, input_type):
         with libpython.FetchAndRestoreError():
             # get the dict of Cython globals and construct a dict in the
             # inferior with Cython locals
@@ -1240,9 +1239,65 @@ class CyExec(CythonCommand, libpython.PyExec):
             try:
                 self._fill_locals_dict(executor,
                                        libpython.pointervalue(local_dict))
-                executor.evalcode(expr, input_type, global_dict, local_dict)
+                result = executor.evalcode(code, input_type, global_dict,
+                                           local_dict)
             finally:
-                executor.decref(libpython.pointervalue(local_dict))
+                executor.xdecref(libpython.pointervalue(local_dict))
+
+        return result
+
+    def evalcode(self, code, input_type):
+        """
+        Evaluate `code` in a Python or Cython stack frame using the given
+        `input_type`.
+        """
+        frame = self._find_first_cython_or_python_frame()
+        executor = libpython.PythonCodeExecutor()
+        if self.is_python_function(frame):
+            return libpython._evalcode_python(executor, code, input_type)
+        return self._evalcode_cython(executor, code, input_type)
+
+
+class CyExec(CythonCommand, libpython.PyExec, EvaluateOrExecuteCodeMixin):
+    """
+    Execute Python code in the nearest Python or Cython frame.
+    """
+
+    name = '-cy-exec'
+    command_class = gdb.COMMAND_STACK
+    completer_class = gdb.COMPLETE_NONE
+
+    def invoke(self, expr, from_tty):
+        expr, input_type = self.readcode(expr)
+        executor = libpython.PythonCodeExecutor()
+        executor.xdecref(self.evalcode(expr, executor.Py_single_input))
+
+
+class CySet(CythonCommand):
+    """
+    Set a Cython variable to a certain value
+
+        cy set my_cython_c_variable = 10
+        cy set my_cython_py_variable = $cy_eval("{'doner': 'kebab'}")
+
+    This is equivalent to
+
+        set $cy_value("my_cython_variable") = 10
+    """
+
+    name = 'cy set'
+    command_class = gdb.COMMAND_DATA
+    completer_class = gdb.COMPLETE_NONE
+
+    @require_cython_frame
+    def invoke(self, expr, from_tty):
+        name_and_expr = expr.split('=', 1)
+        if len(name_and_expr) != 2:
+            raise gdb.GdbError("Invalid expression. Use 'cy set var = expr'.")
+
+        varname, expr = name_and_expr
+        cname = self.cy.cy_cname.invoke(varname.strip())
+        gdb.execute("set %s = %s" % (cname, expr))
 
 
 # Functions
@@ -1312,6 +1367,18 @@ class CyLine(gdb.Function, CythonBase):
     def invoke(self):
         return self.get_cython_lineno()
 
+
+class CyEval(gdb.Function, CythonBase, EvaluateOrExecuteCodeMixin):
+    """
+    Evaluate Python code in the nearest Python or Cython frame and return
+    """
+
+    @gdb_function_value_to_unicode
+    def invoke(self, python_expression):
+        input_type = libpython.PythonCodeExecutor.Py_eval_input
+        return self.evalcode(python_expression, input_type)
+
+
 cython_info = CythonInfo()
 cy = CyCy.register()
 cython_info.cy = cy

Cython/Debugger/libpython.py

@@ -1949,27 +1949,41 @@ class ExecutionControlCommandBase(gdb.Command):
             gdb.execute("delete %s" % bp)
 
     def filter_output(self, result):
-        output = []
-
-        match_finish = re.search(r'^Value returned is \$\d+ = (.*)', result,
-                                 re.MULTILINE)
-        if match_finish:
-            output.append('Value returned: %s' % match_finish.group(1))
-
         reflags = re.MULTILINE
-        regexes = [
+
+        output_on_halt = [
             (r'^Program received signal .*', reflags|re.DOTALL),
             (r'.*[Ww]arning.*', 0),
             (r'^Program exited .*', reflags),
         ]
 
+        output_always = [
+            # output when halting on a watchpoint
+            (r'^(Old|New) value = .*', reflags),
+            # output from the 'display' command
+            (r'^\d+: \w+ = .*', reflags),
+        ]
+
+        def filter_output(regexes):
+            output = []
             for regex, flags in regexes:
-            match = re.search(regex, result, flags)
-            if match:
+                for match in re.finditer(regex, result, flags):
                     output.append(match.group(0))
 
             return '\n'.join(output)
 
+        # Filter the return value output of the 'finish' command
+        match_finish = re.search(r'^Value returned is \$\d+ = (.*)', result,
+                                 re.MULTILINE)
+        if match_finish:
+            finish_output = 'Value returned: %s\n' % match_finish.group(1)
+        else:
+            finish_output = ''
+
+        return (filter_output(output_on_halt),
+                finish_output + filter_output(output_always))
+
+
     def stopped(self):
         return get_selected_inferior().pid == 0
 
@@ -1979,17 +1993,23 @@ class ExecutionControlCommandBase(gdb.Command):
         of source code or the result of the last executed gdb command (passed
         in as the `result` argument).
         """
-        result = self.filter_output(result)
+        output_on_halt, output_always = self.filter_output(result)
 
         if self.stopped():
-            print result.strip()
+            print output_always
+            print output_on_halt
         else:
             frame = gdb.selected_frame()
+            source_line = self.lang_info.get_source_line(frame)
             if self.lang_info.is_relevant_function(frame):
                 raised_exception = self.lang_info.exc_info(frame)
                 if raised_exception:
                     print raised_exception
-                print self.lang_info.get_source_line(frame) or result
+
+            if source_line:
+                if output_always.rstrip():
+                    print output_always.rstrip()
+                print source_line
             else:
                 print result
 
@@ -2190,12 +2210,12 @@ class PythonInfo(LanguageInfo):
         try:
             tstate = frame.read_var('tstate').dereference()
             if gdb.parse_and_eval('tstate->frame == f'):
-                # tstate local variable initialized
+                # tstate local variable initialized, check for an exception
                 inf_type = tstate['curexc_type']
                 inf_value = tstate['curexc_value']
+
                 if inf_type:
-                    return 'An exception was raised: %s(%s)' % (inf_type,
-                                                                inf_value)
+                    return 'An exception was raised: %s' % (inf_value,)
         except (ValueError, RuntimeError), e:
             # Could not read the variable tstate or it's memory, it's ok
             pass
@@ -2342,7 +2362,7 @@ class PythonCodeExecutor(object):
         "Increment the reference count of a Python object in the inferior."
         gdb.parse_and_eval('Py_IncRef((PyObject *) %d)' % pointer)
 
-    def decref(self, pointer):
+    def xdecref(self, pointer):
         "Decrement the reference count of a Python object in the inferior."
         # Py_DecRef is like Py_XDECREF, but a function. So we don't have
         # to check for NULL. This should also decref all our allocated
@@ -2382,10 +2402,11 @@ class PythonCodeExecutor(object):
 
         with FetchAndRestoreError():
             try:
-                self.decref(gdb.parse_and_eval(code))
+                pyobject_return_value = gdb.parse_and_eval(code)
             finally:
                 self.free(pointer)
 
+        return pyobject_return_value
 
 class FetchAndRestoreError(PythonCodeExecutor):
     """
@@ -2462,6 +2483,20 @@ class FixGdbCommand(gdb.Command):
         self.fix_gdb()
 
 
+def _evalcode_python(executor, code, input_type):
+    """
+    Execute Python code in the most recent stack frame.
+    """
+    global_dict = gdb.parse_and_eval('PyEval_GetGlobals()')
+    local_dict = gdb.parse_and_eval('PyEval_GetLocals()')
+
+    if (pointervalue(global_dict) == 0 or pointervalue(local_dict) == 0):
+        raise gdb.GdbError("Unable to find the locals or globals of the "
+                           "most recent Python function (relative to the "
+                           "selected frame).")
+
+    return executor.evalcode(code, input_type, global_dict, local_dict)
+
 class PyExec(gdb.Command):
 
     def readcode(self, expr):
@@ -2484,17 +2519,9 @@ class PyExec(gdb.Command):
 
     def invoke(self, expr, from_tty):
         expr, input_type = self.readcode(expr)
-
         executor = PythonCodeExecutor()
-        global_dict = gdb.parse_and_eval('PyEval_GetGlobals()')
-        local_dict = gdb.parse_and_eval('PyEval_GetLocals()')
-
-        if pointervalue(global_dict) == 0 or pointervalue(local_dict) == 0:
-            raise gdb.GdbError("Unable to find the locals or globals of the "
-                               "most recent Python function (relative to the "
-                               "selected frame).")
-
-        executor.evalcode(expr, input_type, global_dict, local_dict)
+        executor.xdecref(_evalcode_python(executor, input_type, global_dict,
+                                          local_dict))
 
 
 gdb.execute('set breakpoint pending on')