[analyzer] Anti-aliasing: different heap allocations do not alias

Add a concept of symbolic memory region belonging to heap memory space.
When comparing symbolic regions allocated on the heap, assume that they
do not alias. 

Use symbolic heap region to suppress a common false positive pattern in
the malloc checker, in code that relies on malloc not returning the
memory aliased to other malloc allocations, stack.

llvm-svn: 158136

1 files changed, 12 insertions, 0 deletions

diff --git a/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp b/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
index 765ae48c73e..c391489beb1 100644
--- a/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
+++ b/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
@@ -148,6 +148,18 @@ SValBuilder::getConjuredSymbolVal(const Stmt *stmt,
   return nonloc::SymbolVal(sym);
 }
 
+DefinedOrUnknownSVal
+SValBuilder::getConjuredHeapSymbolVal(const Expr *E,
+                                      const LocationContext *LCtx,
+                                      unsigned VisitCount) {
+  QualType T = E->getType();
+  assert(Loc::isLocType(T));
+  assert(SymbolManager::canSymbolicate(T));
+
+  SymbolRef sym = SymMgr.getConjuredSymbol(E, LCtx, T, VisitCount);
+  return loc::MemRegionVal(MemMgr.getSymbolicHeapRegion(sym));
+}
+
 DefinedSVal SValBuilder::getMetadataSymbolVal(const void *symbolTag,
                                               const MemRegion *region,
                                               const Expr *expr, QualType type,