[analyzer] Add LocationContext information to SymbolMetadata.

Like SymbolConjured, SymbolMetadata also needs to be uniquely
identified by the moment of its birth.

Such moments are coded by the (Statement, LocationContext, Block count) triples.
Each such triple represents the moment of analyzing a statement with a certain
call backtrace, with corresponding CFG block having been entered a given amount
of times during analysis of the current code body.

The LocationContext information was accidentally omitted for SymbolMetadata,
which leads to reincarnation of SymbolMetadata upon re-entering a code body
with a different backtrace; the new symbol is incorrectly unified with
the old symbol, which leads to unsound assumptions.

Patch by Alexey Sidorin!

Differential Revision: https://reviews.llvm.org/D21978

llvm-svn: 278937

6 files changed, 41 insertions, 13 deletions

diff --git a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h
index e4be349c026..9b55b3cc02e 100644
--- a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h
+++ b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h
@@ -198,9 +198,11 @@ public:
   DefinedOrUnknownSVal getDerivedRegionValueSymbolVal(
       SymbolRef parentSymbol, const TypedValueRegion *region);
 
-  DefinedSVal getMetadataSymbolVal(
-      const void *symbolTag, const MemRegion *region,
-      const Expr *expr, QualType type, unsigned count);
+  DefinedSVal getMetadataSymbolVal(const void *symbolTag,
+                                   const MemRegion *region,
+                                   const Expr *expr, QualType type,
+                                   const LocationContext *LCtx,
+                                   unsigned count);
 
   DefinedSVal getFunctionPointer(const FunctionDecl *func);
   
diff --git a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h
index 087430583e0..f00dce568e3 100644
--- a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h
+++ b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h
@@ -186,15 +186,18 @@ class SymbolMetadata : public SymbolData {
   const MemRegion* R;
   const Stmt *S;
   QualType T;
+  const LocationContext *LCtx;
   unsigned Count;
   const void *Tag;
 public:
   SymbolMetadata(SymbolID sym, const MemRegion* r, const Stmt *s, QualType t,
-                 unsigned count, const void *tag)
-  : SymbolData(SymbolMetadataKind, sym), R(r), S(s), T(t), Count(count), Tag(tag) {}
+                 const LocationContext *LCtx, unsigned count, const void *tag)
+  : SymbolData(SymbolMetadataKind, sym), R(r), S(s), T(t), LCtx(LCtx),
+    Count(count), Tag(tag) {}
 
   const MemRegion *getRegion() const { return R; }
   const Stmt *getStmt() const { return S; }
+  const LocationContext *getLocationContext() const { return LCtx; }
   unsigned getCount() const { return Count; }
   const void *getTag() const { return Tag; }
 
@@ -203,18 +206,19 @@ public:
   void dumpToStream(raw_ostream &os) const override;
 
   static void Profile(llvm::FoldingSetNodeID& profile, const MemRegion *R,
-                      const Stmt *S, QualType T, unsigned Count,
-                      const void *Tag) {
+                      const Stmt *S, QualType T, const LocationContext *LCtx,
+                      unsigned Count, const void *Tag) {
     profile.AddInteger((unsigned) SymbolMetadataKind);
     profile.AddPointer(R);
     profile.AddPointer(S);
     profile.Add(T);
+    profile.AddPointer(LCtx);
     profile.AddInteger(Count);
     profile.AddPointer(Tag);
   }
 
   void Profile(llvm::FoldingSetNodeID& profile) override {
-    Profile(profile, R, S, T, Count, Tag);
+    Profile(profile, R, S, T, LCtx, Count, Tag);
   }
 
   // Implement isa<T> support.
@@ -435,7 +439,9 @@ public:
   /// VisitCount can be used to differentiate regions corresponding to
   /// different loop iterations, thus, making the symbol path-dependent.
   const SymbolMetadata *getMetadataSymbol(const MemRegion *R, const Stmt *S,
-                                          QualType T, unsigned VisitCount,
+                                          QualType T,
+                                          const LocationContext *LCtx,
+                                          unsigned VisitCount,
                                           const void *SymbolTag = nullptr);
 
   const SymbolCast* getCastSymbol(const SymExpr *Operand,
diff --git a/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
index 1f13dbad6fd..7cdbe88e88f 100644
--- a/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
@@ -685,6 +685,7 @@ SVal CStringChecker::getCStringLengthForRegion(CheckerContext &C,
   QualType sizeTy = svalBuilder.getContext().getSizeType();
   SVal strLength = svalBuilder.getMetadataSymbolVal(CStringChecker::getTag(),
                                                     MR, Ex, sizeTy,
+                                                    C.getLocationContext(),
                                                     C.blockCount());
 
   if (!hypothetical) {
diff --git a/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp b/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
index 72bcdd9ecb0..fe9a6834f6a 100644
--- a/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
+++ b/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
@@ -182,11 +182,12 @@ SValBuilder::getConjuredHeapSymbolVal(const Expr *E,
 DefinedSVal SValBuilder::getMetadataSymbolVal(const void *symbolTag,
                                               const MemRegion *region,
                                               const Expr *expr, QualType type,
+                                              const LocationContext *LCtx,
                                               unsigned count) {
   assert(SymbolManager::canSymbolicate(type) && "Invalid metadata symbol type");
 
   SymbolRef sym =
-      SymMgr.getMetadataSymbol(region, expr, type, count, symbolTag);
+      SymMgr.getMetadataSymbol(region, expr, type, LCtx, count, symbolTag);
 
   if (Loc::isLocType(type))
     return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
diff --git a/clang/lib/StaticAnalyzer/Core/SymbolManager.cpp b/clang/lib/StaticAnalyzer/Core/SymbolManager.cpp
index b8b4af1179e..6b99ca510be 100644
--- a/clang/lib/StaticAnalyzer/Core/SymbolManager.cpp
+++ b/clang/lib/StaticAnalyzer/Core/SymbolManager.cpp
@@ -216,17 +216,18 @@ SymbolManager::getExtentSymbol(const SubRegion *R) {
   return cast<SymbolExtent>(SD);
 }
 
-const SymbolMetadata*
+const SymbolMetadata *
 SymbolManager::getMetadataSymbol(const MemRegion* R, const Stmt *S, QualType T,
+                                 const LocationContext *LCtx,
                                  unsigned Count, const void *SymbolTag) {
 
   llvm::FoldingSetNodeID profile;
-  SymbolMetadata::Profile(profile, R, S, T, Count, SymbolTag);
+  SymbolMetadata::Profile(profile, R, S, T, LCtx, Count, SymbolTag);
   void *InsertPos;
   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
   if (!SD) {
     SD = (SymExpr*) BPAlloc.Allocate<SymbolMetadata>();
-    new (SD) SymbolMetadata(SymbolCounter, R, S, T, Count, SymbolTag);
+    new (SD) SymbolMetadata(SymbolCounter, R, S, T, LCtx, Count, SymbolTag);
     DataSet.InsertNode(SD, InsertPos);
     ++SymbolCounter;
   }
diff --git a/clang/test/Analysis/string.c b/clang/test/Analysis/string.c
index 2803362ba43..e541219d05a 100644
--- a/clang/test/Analysis/string.c
+++ b/clang/test/Analysis/string.c
@@ -154,6 +154,23 @@ void strlen_liveness(const char *x) {
   clang_analyzer_eval(strlen(x) < 5); // expected-warning{{FALSE}}
 }
 
+
+size_t strlenWrapper(const char *str) {
+  return strlen(str);
+}
+
+extern void invalidate(char *s);
+
+void testStrlenCallee() {
+  char str[42];
+  invalidate(str);
+  size_t lenBefore = strlenWrapper(str);
+  invalidate(str);
+  size_t lenAfter = strlenWrapper(str);
+  clang_analyzer_eval(lenBefore == lenAfter); // expected-warning{{UNKNOWN}}
+}
+
+
 //===----------------------------------------------------------------------===
 // strnlen()
 //===----------------------------------------------------------------------===