Issue 2149: Avoid reference cycles caused by frame objects

3 files changed, 11 insertions, 3 deletions

diff --git a/src/engine/SCons/Defaults.py b/src/engine/SCons/Defaults.py
index 067f22d..b790a49 100644
--- a/src/engine/SCons/Defaults.py
+++ b/src/engine/SCons/Defaults.py
@@ -424,7 +424,10 @@ class Variable_Method_Caller:
         self.method = method
     def __call__(self, *args, **kw):
         try: 1/0
-        except ZeroDivisionError: frame = sys.exc_info()[2].tb_frame
+        except ZeroDivisionError: 
+            # Don't start iterating with the current stack-frame to
+            # prevent creating reference cycles (f_back is safe).
+            frame = sys.exc_info()[2].tb_frame.f_back
         variable = self.variable
         while frame:
             if frame.f_locals.has_key(variable):
diff --git a/src/engine/SCons/SConf.py b/src/engine/SCons/SConf.py
index b964307..9b3879e 100644
--- a/src/engine/SCons/SConf.py
+++ b/src/engine/SCons/SConf.py
@@ -235,7 +235,9 @@ class SConfBuildTask(SCons.Taskmaster.Task):
             raise
         elif issubclass(exc_type, SCons.Errors.BuildError):
             # we ignore Build Errors (occurs, when a test doesn't pass)
-            pass
+            # Clear the exception to prevent the contained traceback
+            # to build a reference cycle.
+            self.exc_clear()
         else:
             self.display('Caught exception while building "%s":\n' %
                          self.targets[0])
diff --git a/src/engine/SCons/Script/SConscript.py b/src/engine/SCons/Script/SConscript.py
index 7e38ffd..5cfde64 100644
--- a/src/engine/SCons/Script/SConscript.py
+++ b/src/engine/SCons/Script/SConscript.py
@@ -81,7 +81,10 @@ def get_calling_namespaces():
     """Return the locals and globals for the function that called
     into this module in the current call stack."""
     try: 1/0
-    except ZeroDivisionError: frame = sys.exc_info()[2].tb_frame
+    except ZeroDivisionError: 
+        # Don't start iterating with the current stack-frame to
+        # prevent creating reference cycles (f_back is safe).
+        frame = sys.exc_info()[2].tb_frame.f_back
 
     # Find the first frame that *isn't* from this file.  This means
     # that we expect all of the SCons frames that implement an Export()