From cf9ff89663d7fac3759eb2b0bb9030a7bf97e47f Mon Sep 17 00:00:00 2001
From: George Karpenkov <ekarpenkov@apple.com>
Date: Wed, 17 Jan 2018 20:27:26 +0000
Subject: [PATCH] [analyzer] Make isSubRegionOf reflexive

All usages of isSubRegionOf separately check for reflexive case, and in
any case, set theory tells us that each set is a subset of itself.

Differential Revision: https://reviews.llvm.org/D42140

llvm-svn: 322752
---
 clang/include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h | 1 +
 clang/lib/StaticAnalyzer/Checkers/MisusedMovedObjectChecker.cpp   | 2 --
 clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp             | 2 +-
 clang/lib/StaticAnalyzer/Core/MemRegion.cpp                       | 6 +++---
 clang/lib/StaticAnalyzer/Core/ProgramState.cpp                    | 3 +--
 clang/lib/StaticAnalyzer/Core/RegionStore.cpp                     | 4 ++--
 6 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h
index 8ab6656..ac214c2 100644
--- a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h
+++ b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h
@@ -103,6 +103,7 @@ public:
   const MemRegion *getBaseRegion() const;
 
   /// Check if the region is a subregion of the given region.
+  /// Each region is a subregion of itself.
   virtual bool isSubRegionOf(const MemRegion *R) const;
 
   const MemRegion *StripCasts(bool StripBaseCasts = true) const;
diff --git a/clang/lib/StaticAnalyzer/Checkers/MisusedMovedObjectChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/MisusedMovedObjectChecker.cpp
index 497978f..c6493fe 100644
--- a/clang/lib/StaticAnalyzer/Checkers/MisusedMovedObjectChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/MisusedMovedObjectChecker.cpp
@@ -101,8 +101,6 @@ static ProgramStateRef removeFromState(ProgramStateRef State,
                                        const MemRegion *Region) {
   if (!Region)
     return State;
-  // Note: The isSubRegionOf function is not reflexive.
-  State = State->remove<TrackedRegionMap>(Region);
   for (auto &E : State->get<TrackedRegionMap>()) {
     if (E.first->isSubRegionOf(Region))
       State = State->remove<TrackedRegionMap>(E.first);
diff --git a/clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp b/clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
index 3eaa20d..6b9aaa6 100644
--- a/clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
+++ b/clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
@@ -1838,7 +1838,7 @@ UndefOrNullArgVisitor::VisitNode(const ExplodedNode *N,
     const MemRegion *ArgReg = Call->getArgSVal(Idx).getAsRegion();
 
     // Are we tracking the argument or its subregion?
-    if ( !ArgReg || (ArgReg != R && !R->isSubRegionOf(ArgReg->StripCasts())))
+    if ( !ArgReg || !R->isSubRegionOf(ArgReg->StripCasts()))
       continue;
 
     // Check the function parameter type.
diff --git a/clang/lib/StaticAnalyzer/Core/MemRegion.cpp b/clang/lib/StaticAnalyzer/Core/MemRegion.cpp
index cb8ba6d..aa54544 100644
--- a/clang/lib/StaticAnalyzer/Core/MemRegion.cpp
+++ b/clang/lib/StaticAnalyzer/Core/MemRegion.cpp
@@ -103,15 +103,15 @@ MemRegionManager::~MemRegionManager() {
 //===----------------------------------------------------------------------===//
 
 bool SubRegion::isSubRegionOf(const MemRegion* R) const {
-  const MemRegion* r = getSuperRegion();
-  while (r != nullptr) {
+  const MemRegion* r = this;
+  do {
     if (r == R)
       return true;
     if (const SubRegion* sr = dyn_cast<SubRegion>(r))
       r = sr->getSuperRegion();
     else
       break;
-  }
+  } while (r != nullptr);
   return false;
 }
 
diff --git a/clang/lib/StaticAnalyzer/Core/ProgramState.cpp b/clang/lib/StaticAnalyzer/Core/ProgramState.cpp
index 5b6b733..871bbf0 100644
--- a/clang/lib/StaticAnalyzer/Core/ProgramState.cpp
+++ b/clang/lib/StaticAnalyzer/Core/ProgramState.cpp
@@ -781,8 +781,7 @@ bool ProgramState::isTainted(SymbolRef Sym, TaintTagType Kind) const {
           // complete. For example, this would not currently identify
           // overlapping fields in a union as tainted. To identify this we can
           // check for overlapping/nested byte offsets.
-          if (Kind == I.second &&
-              (R == I.first || R->isSubRegionOf(I.first)))
+          if (Kind == I.second && R->isSubRegionOf(I.first))
             return true;
         }
       }
diff --git a/clang/lib/StaticAnalyzer/Core/RegionStore.cpp b/clang/lib/StaticAnalyzer/Core/RegionStore.cpp
index e2e69bb..604adde 100644
--- a/clang/lib/StaticAnalyzer/Core/RegionStore.cpp
+++ b/clang/lib/StaticAnalyzer/Core/RegionStore.cpp
@@ -871,7 +871,7 @@ collectSubRegionBindings(SmallVectorImpl<BindingPair> &Bindings,
 
     } else if (NextKey.hasSymbolicOffset()) {
       const MemRegion *Base = NextKey.getConcreteOffsetRegion();
-      if (Top->isSubRegionOf(Base)) {
+      if (Top->isSubRegionOf(Base) && Top != Base) {
         // Case 3: The next key is symbolic and we just changed something within
         // its concrete region. We don't know if the binding is still valid, so
         // we'll be conservative and include it.
@@ -881,7 +881,7 @@ collectSubRegionBindings(SmallVectorImpl<BindingPair> &Bindings,
       } else if (const SubRegion *BaseSR = dyn_cast<SubRegion>(Base)) {
         // Case 4: The next key is symbolic, but we changed a known
         // super-region. In this case the binding is certainly included.
-        if (Top == Base || BaseSR->isSubRegionOf(Top))
+        if (BaseSR->isSubRegionOf(Top))
           if (isCompatibleWithFields(NextKey, FieldsInSymbolicSubregions))
             Bindings.push_back(*I);
       }
-- 
2.7.4