[analyzer] Create a temporary region for rvalue structs when accessing fields

Struct rvalues are represented in the analyzer by CompoundVals,
LazyCompoundVals, or plain ConjuredSymbols -- none of which have associated
regions. If the entire structure is going to persist, this is not a
problem -- either the rvalue will be assigned to an existing region, or
a MaterializeTemporaryExpr will be present to create a temporary region.
However, if we just need a field from the struct, we need to create the
temporary region ourselves.

This is inspired by the way CodeGen handles calls to temporaries;
support for that in the analyzer is coming next.

Part of <rdar://problem/12137950>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@164828 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 9 deletions

diff --git a/lib/StaticAnalyzer/Core/ExprEngine.cpp b/lib/StaticAnalyzer/Core/ExprEngine.cpp
index 8e2c159ca7..06216f83ea 100644
--- a/lib/StaticAnalyzer/Core/ExprEngine.cpp
+++ b/lib/StaticAnalyzer/Core/ExprEngine.cpp
@@ -1505,17 +1505,17 @@ void ExprEngine::VisitMemberExpr(const MemberExpr *M, ExplodedNode *Pred,
   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()));
-    return;
+
+  // If we're accessing a field of an rvalue, we need to treat it like a
+  // temporary object.
+  if (isa<NonLoc>(baseExprVal)) {
+    const MemRegion *R  =
+      svalBuilder.getRegionManager().getCXXTempObjectRegion(baseExpr, LCtx);
+    SVal L = loc::MemRegionVal(R);
+    state = state->bindLoc(L, baseExprVal);
+    baseExprVal = L;
   }
 
-  // For all other cases, compute an lvalue.    
   SVal L = state->getLValue(field, baseExprVal);
   if (M->isGLValue()) {
     ExplodedNodeSet Tmp;