[analyzer] Create a temporary region when accessing a struct rvalue.

In C++, rvalues that need to have their address taken (for example, to be
passed to a function by const reference) will be wrapped in a
MaterializeTemporaryExpr, which lets CodeGen know to create a temporary
region to store this value. However, MaterializeTemporaryExprs are /not/
created when a method is called on an rvalue struct, even though the 'this'
pointer needs a valid value. CodeGen works around this by creating a
temporary region anyway; now, so does the analyzer.

The analyzer also does this when accessing a field of a struct rvalue.
This is a little unfortunate, since the rest of the struct will soon be
thrown away, but it does make things consistent with the rest of the
analyzer.

This allows us to bring back the assumption that all known 'this' values
are Locs. This is a revised version of r164828-9, reverted in r164876-7.

<rdar://problem/12137950>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@166120 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 50 insertions, 27 deletions

diff --git a/lib/StaticAnalyzer/Core/ExprEngine.cpp b/lib/StaticAnalyzer/Core/ExprEngine.cpp
index 007bcf5208..213ab7ad5c 100644
--- a/lib/StaticAnalyzer/Core/ExprEngine.cpp
+++ b/lib/StaticAnalyzer/Core/ExprEngine.cpp
@@ -163,6 +163,23 @@ ProgramStateRef ExprEngine::getInitialState(const LocationContext *InitLoc) {
   return state;
 }
 
+/// If the value of the given expression is a NonLoc, copy it into a new
+/// temporary region, and replace the value of the expression with that.
+static ProgramStateRef createTemporaryRegionIfNeeded(ProgramStateRef State,
+                                                     const LocationContext *LC,
+                                                     const Expr *E) {
+  SVal V = State->getSVal(E, LC);
+
+  if (isa<NonLoc>(V)) {
+    MemRegionManager &MRMgr = State->getStateManager().getRegionManager();
+    const MemRegion *R  = MRMgr.getCXXTempObjectRegion(E, LC);
+    State = State->bindLoc(loc::MemRegionVal(R), V);
+    State = State->BindExpr(E, LC, loc::MemRegionVal(R));
+  }
+
+  return State;
+}
+
 //===----------------------------------------------------------------------===//
 // Top-level transfer function logic (Dispatcher).
 //===----------------------------------------------------------------------===//
@@ -717,8 +734,26 @@ void ExprEngine::Visit(const Stmt *S, ExplodedNode *Pred,
       break;
     }
 
+    case Stmt::CXXOperatorCallExprClass: {
+      const CXXOperatorCallExpr *OCE = cast<CXXOperatorCallExpr>(S);
+
+      // For instance method operators, make sure the 'this' argument has a
+      // valid region.
+      const Decl *Callee = OCE->getCalleeDecl();
+      if (const CXXMethodDecl *MD = dyn_cast_or_null<CXXMethodDecl>(Callee)) {
+        if (MD->isInstance()) {
+          ProgramStateRef State = Pred->getState();
+          const LocationContext *LCtx = Pred->getLocationContext();
+          ProgramStateRef NewState =
+            createTemporaryRegionIfNeeded(State, LCtx, OCE->getArg(0));
+          if (NewState != State)
+            Pred = Bldr.generateNode(OCE, Pred, NewState, /*Tag=*/0,
+                                     ProgramPoint::PreStmtKind);
+        }
+      }
+      // FALLTHROUGH
+    }
     case Stmt::CallExprClass:
-    case Stmt::CXXOperatorCallExprClass:
     case Stmt::CXXMemberCallExprClass:
     case Stmt::UserDefinedLiteralClass: {
       Bldr.takeNodes(Pred);
@@ -1478,6 +1513,7 @@ void ExprEngine::VisitMemberExpr(const MemberExpr *M, ExplodedNode *Pred,
   ExplodedNodeSet Dst;
   Decl *member = M->getMemberDecl();
 
+  // Handle static member variables accessed via member syntax.
   if (VarDecl *VD = dyn_cast<VarDecl>(member)) {
     assert(M->isGLValue());
     Bldr.takeNodes(Pred);
@@ -1486,40 +1522,27 @@ void ExprEngine::VisitMemberExpr(const MemberExpr *M, ExplodedNode *Pred,
     return;
   }
 
+  ProgramStateRef state = Pred->getState();
+  const LocationContext *LCtx = Pred->getLocationContext();
+  Expr *BaseExpr = M->getBase();
+
   // Handle C++ method calls.
   if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(member)) {
-    Bldr.takeNodes(Pred);
-    SVal MDVal = svalBuilder.getFunctionPointer(MD);
-    ProgramStateRef state =
-      Pred->getState()->BindExpr(M, Pred->getLocationContext(), MDVal);
-    Bldr.generateNode(M, Pred, state);
-    return;
-  }
-
+    if (MD->isInstance())
+      state = createTemporaryRegionIfNeeded(state, LCtx, BaseExpr);
 
-  FieldDecl *field = dyn_cast<FieldDecl>(member);
-  if (!field) // FIXME: skipping member expressions for non-fields
-    return;
+    SVal MDVal = svalBuilder.getFunctionPointer(MD);
+    state = state->BindExpr(M, LCtx, MDVal);
 
-  Expr *baseExpr = M->getBase()->IgnoreParens();
-  ProgramStateRef state = Pred->getState();
-  const LocationContext *LCtx = Pred->getLocationContext();
-  SVal baseExprVal = state->getSVal(baseExpr, Pred->getLocationContext());
-  if (isa<nonloc::LazyCompoundVal>(baseExprVal) ||
-      isa<nonloc::CompoundVal>(baseExprVal) ||
-      // FIXME: This can originate by conjuring a symbol for an unknown
-      // temporary struct object, see test/Analysis/fields.c:
-      // (p = getit()).x
-      isa<nonloc::SymbolVal>(baseExprVal)) {
-    Bldr.generateNode(M, Pred, state->BindExpr(M, LCtx, UnknownVal()));
+    Bldr.generateNode(M, Pred, state);
     return;
   }
 
-  // FIXME: Should we insert some assumption logic in here to determine
-  // if "Base" is a valid piece of memory?  Before we put this assumption
-  // later when using FieldOffset lvals (which we no longer have).
+  // Handle regular struct fields / member variables.
+  state = createTemporaryRegionIfNeeded(state, LCtx, BaseExpr);
+  SVal baseExprVal = state->getSVal(BaseExpr, LCtx);
 
-  // For all other cases, compute an lvalue.    
+  FieldDecl *field = cast<FieldDecl>(member);
   SVal L = state->getLValue(field, baseExprVal);
   if (M->isGLValue()) {
     if (field->getType()->isReferenceType()) {