Modernize multple calls to init/del

Author: joefarebrother

python/ql/lib/semmle/python/dataflow/new/internal/DataFlowDispatch.qll

@@ -851,9 +851,14 @@ Class getNextClassInMroKnownStartingClass(Class cls, Class startingClass) {
   )
 }
 
-private Function findFunctionAccordingToMroKnownStartingClass(
-  Class cls, Class startingClass, string name
-) {
+/**
+ * Gets a potential definition of the function `name` of the class `cls` according to our approximation of
+ * MRO for the class `startingCls` (see `getNextClassInMroKnownStartingClass` for more information).
+ *
+ * Note: this is almost the same as `findFunctionAccordingToMro`, except we know the
+ * `startingClass`, which can give slightly more precise results.
+ */
+Function findFunctionAccordingToMroKnownStartingClass(Class cls, Class startingClass, string name) {
   result = cls.getAMethod() and
   result.getName() = name and
   cls = getADirectSuperclass*(startingClass)
@@ -866,7 +871,7 @@ private Function findFunctionAccordingToMroKnownStartingClass(
 
 /**
  * Gets a potential definition of the function `name` according to our approximation of
- * MRO for the class `cls` (see `getNextClassInMroKnownStartingClass` for more information).
+ * MRO for the class `startingCls` (see `getNextClassInMroKnownStartingClass` for more information).
  *
  * Note: this is almost the same as `findFunctionAccordingToMro`, except we know the
  * `startingClass`, which can give slightly more precise results.

python/ql/src/Classes/CallsToInitDel/MethodCallOrder.qll

@@ -4,37 +4,32 @@ import python
 import semmle.python.ApiGraphs
 import semmle.python.dataflow.new.internal.DataFlowDispatch
 
-// Helper predicates for multiple call to __init__/__del__ queries.
-pragma[noinline]
-private predicate multiple_invocation_paths_helper(
-  FunctionInvocation top, FunctionInvocation i1, FunctionInvocation i2, FunctionObject multi
-) {
-  i1 != i2 and
-  i1 = top.getACallee+() and
-  i2 = top.getACallee+() and
-  i1.getFunction() = multi
-}
-
-pragma[noinline]
-private predicate multiple_invocation_paths(
-  FunctionInvocation top, FunctionInvocation i1, FunctionInvocation i2, FunctionObject multi
-) {
-  multiple_invocation_paths_helper(top, i1, i2, multi) and
-  i2.getFunction() = multi
+predicate multipleCallsToSuperclassMethod(Function meth, Function calledMulti, string name) {
+  exists(DataFlow::MethodCallNode call1, DataFlow::MethodCallNode call2, Class cls |
+    meth.getName() = name and
+    meth.getScope() = cls and
+    not call1 = call2 and
+    calledMulti = getASuperCallTarget(cls, meth, call1) and
+    calledMulti = getASuperCallTarget(cls, meth, call2) and
+    nonTrivial(calledMulti)
+  )
 }
 
-/** Holds if `self.name` calls `multi` by multiple paths, and thus calls it more than once. */
-predicate multiple_calls_to_superclass_method(ClassObject self, FunctionObject multi, string name) {
-  exists(FunctionInvocation top, FunctionInvocation i1, FunctionInvocation i2 |
-    multiple_invocation_paths(top, i1, i2, multi) and
-    top.runtime(self.declaredAttribute(name)) and
-    self.getASuperType().declaredAttribute(name) = multi
+Function getASuperCallTarget(Class mroBase, Function meth, DataFlow::MethodCallNode call) {
+  meth = call.getScope() and
+  getADirectSuperclass*(mroBase) = meth.getScope() and
+  call.calls(_, meth.getName()) and
+  exists(Function target, Class nextMroBase |
+    (result = target or result = getASuperCallTarget(nextMroBase, target, _))
   |
-    // Only called twice if called from different functions,
-    // or if one call-site can reach the other.
-    i1.getCall().getScope() != i2.getCall().getScope()
+    superCall(call, _) and
+    nextMroBase = mroBase and
+    target =
+      findFunctionAccordingToMroKnownStartingClass(getNextClassInMroKnownStartingClass(meth.getScope(),
+          mroBase), mroBase, meth.getName())
     or
-    i1.getCall().strictlyReaches(i2.getCall())
+    callsMethodOnClassWithSelf(meth, call, nextMroBase, _) and
+    target = findFunctionAccordingToMro(nextMroBase, meth.getName())
   )
 }
 

python/ql/src/Classes/CallsToInitDel/SuperclassDelCalledMultipleTimes.ql

@@ -1,6 +1,6 @@
 /**
  * @name Multiple calls to `__del__` during object destruction
- * @description A duplicated call to a super-class `__del__` method may lead to class instances not be cleaned up properly.
+ * @description A duplicated call to a superclass `__del__` method may lead to class instances not be cleaned up properly.
  * @kind problem
  * @tags quality
  *       reliability
@@ -14,16 +14,17 @@
 import python
 import MethodCallOrder
 
-from ClassObject self, FunctionObject multi
+predicate multipleCallsToSuperclassDel(Function meth, Function calledMulti) {
+  multipleCallsToSuperclassMethod(meth, calledMulti, "__sel__")
+}
+
+from Function meth, Function calledMulti
 where
-  multiple_calls_to_superclass_method(self, multi, "__del__") and
-  not multiple_calls_to_superclass_method(self.getABaseType(), multi, "__del__") and
-  not exists(FunctionObject better |
-    multiple_calls_to_superclass_method(self, better, "__del__") and
-    better.overrides(multi)
-  ) and
-  not self.failedInference()
-select self,
-  "Class " + self.getName() +
-    " may not be cleaned up properly as $@ may be called multiple times during destruction.", multi,
-  multi.descriptiveString()
+  multipleCallsToSuperclassDel(meth, calledMulti) and
+  // Don't alert for multiple calls to a superclass del when a subclass will do.
+  not exists(Function subMulti |
+    multipleCallsToSuperclassDel(meth, subMulti) and
+    calledMulti.getScope() = getADirectSuperclass+(subMulti.getScope())
+  )
+select meth, "This delete method calls $@ multiple times.", calledMulti,
+  calledMulti.getQualifiedName()

python/ql/src/Classes/CallsToInitDel/SuperclassInitCalledMultipleTimes.ql

@@ -1,6 +1,6 @@
 /**
  * @name Multiple calls to `__init__` during object initialization
- * @description A duplicated call to a super-class `__init__` method may lead to objects of this class not being properly initialized.
+ * @description A duplicated call to a superclass `__init__` method may lead to objects of this class not being properly initialized.
  * @kind problem
  * @tags quality
  *       reliability
@@ -14,17 +14,17 @@
 import python
 import MethodCallOrder
 
-from ClassObject self, FunctionObject multi
+predicate multipleCallsToSuperclassInit(Function meth, Function calledMulti) {
+  multipleCallsToSuperclassMethod(meth, calledMulti, "__init__")
+}
+
+from Function meth, Function calledMulti
 where
-  multi != theObjectType().lookupAttribute("__init__") and
-  multiple_calls_to_superclass_method(self, multi, "__init__") and
-  not multiple_calls_to_superclass_method(self.getABaseType(), multi, "__init__") and
-  not exists(FunctionObject better |
-    multiple_calls_to_superclass_method(self, better, "__init__") and
-    better.overrides(multi)
-  ) and
-  not self.failedInference()
-select self,
-  "Class " + self.getName() +
-    " may not be initialized properly as $@ may be called multiple times during initialization.",
-  multi, multi.descriptiveString()
+  multipleCallsToSuperclassInit(meth, calledMulti) and
+  // Don't alert for multiple calls to a superclass init when a subclass will do.
+  not exists(Function subMulti |
+    multipleCallsToSuperclassInit(meth, subMulti) and
+    calledMulti.getScope() = getADirectSuperclass+(subMulti.getScope())
+  )
+select meth, "This initializer method calls $@ multiple times.", calledMulti,
+  calledMulti.getQualifiedName()