[analyzer] Allow TrackConstraintBRVisitor to work when the value it’s tracking is not live in the last node of the path

We always register the visitor on a node in which the value we are tracking is live and constrained. However,
the visitation can restart at a node, later on the path, in which the value is under constrained because
it is no longer live. Previously, we just silently stopped tracking in that case.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179731 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 2 deletions

diff --git a/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp b/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
index 18994ca0d0..11a1727645 100644
--- a/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
+++ b/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
@@ -699,6 +699,14 @@ TrackConstraintBRVisitor::VisitNode(const ExplodedNode *N,
   if (IsSatisfied)
     return NULL;
 
+  // Start tracking after we see the first state in which the value is
+  // constrained.
+  if (!IsTrackingTurnedOn)
+    if (!isUnderconstrained(N))
+      IsTrackingTurnedOn = true;
+  if (!IsTrackingTurnedOn)
+    return 0;
+
   // Check if in the previous state it was feasible for this constraint
   // to *not* be true.
   if (isUnderconstrained(PrevN)) {
@@ -708,8 +716,7 @@ TrackConstraintBRVisitor::VisitNode(const ExplodedNode *N,
     // As a sanity check, make sure that the negation of the constraint
     // was infeasible in the current state.  If it is feasible, we somehow
     // missed the transition point.
-    if (isUnderconstrained(N))
-      return NULL;
+    assert(!isUnderconstrained(N));
 
     // We found the transition point for the constraint.  We now need to
     // pretty-print the constraint. (work-in-progress)