[analyzer] If we call a C++ method on an object, assume it's non-null.

This is analogous to our handling of pointer dereferences: if we
dereference a pointer that may or may not be null, we assume it's non-null
from then on.

While some implementations of C++ (including ours) allow you to call a
non-virtual method through a null pointer of object type, it is technically
disallowed by the C++ standard, and should not prune out any real paths in
practice.

  [class.mfct.non-static]p1: A non-static member function may be called
    for an object of its class type, or for an object of a class derived
    from its class type...
  (a null pointer value does not refer to an object)

We can also make the same assumption about function pointers.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@161992 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 3 deletions

diff --git a/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp b/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
index 30f45c7685..5edcf09f11 100644
--- a/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
@@ -235,17 +235,20 @@ void CallAndMessageChecker::checkPreStmt(const CallExpr *CE,
   ProgramStateRef StNonNull, StNull;
   llvm::tie(StNonNull, StNull) = State->assume(cast<DefinedOrUnknownSVal>(L));
 
-  // FIXME: Do we want to record the non-null assumption here?
   if (StNull && !StNonNull) {
     if (!BT_call_null)
       BT_call_null.reset(
         new BuiltinBug("Called function pointer is null (null dereference)"));
     emitBadCall(BT_call_null.get(), C, Callee);
   }
+
+  C.addTransition(StNonNull);
 }
 
 void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
                                          CheckerContext &C) const {
+  ProgramStateRef State = C.getState();
+
   // If this is a call to a C++ method, check if the callee is null or
   // undefined.
   if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) {
@@ -258,11 +261,9 @@ void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
       return;
     }
 
-    ProgramStateRef State = C.getState();
     ProgramStateRef StNonNull, StNull;
     llvm::tie(StNonNull, StNull) = State->assume(cast<DefinedOrUnknownSVal>(V));
 
-    // FIXME: Do we want to record the non-null assumption here?
     if (StNull && !StNonNull) {
       if (!BT_cxx_call_null)
         BT_cxx_call_null.reset(new BuiltinBug("Called C++ object pointer "
@@ -270,6 +271,8 @@ void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
       emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr());
       return;
     }
+
+    State = StNonNull;
   }
 
   // Don't check for uninitialized field values in arguments if the
@@ -291,6 +294,9 @@ void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
                            Call.getArgExpr(i), /*IsFirstArgument=*/i == 0,
                            checkUninitFields, Call, *BT))
       return;
+
+  // If we make it here, record our assumptions about the callee.
+  C.addTransition(State);
 }
 
 void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg,