[analyzer] Destroy and lifetime-extend inlined function return values properly.

This patch uses the newly added CFGCXXRecordTypedCall element at the call site
of the caller to construct the return value within the callee directly into the
caller's stack frame. This way it is also capable of populating the temporary
destructor and lifetime extension maps for the temporary, which allows
temporary destructors and lifetime extension to work correctly.

This patch does not affect temporaries that were returned from conservatively
evaluated functions.

Differential Revision: https://reviews.llvm.org/D44124

llvm-svn: 327345

1 files changed, 58 insertions, 29 deletions

diff --git a/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp b/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
index f4aa56f2750..398bb978fc5 100644
--- a/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
+++ b/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
@@ -197,16 +197,19 @@ ExprEngine::getRegionForConstructedObject(const CXXConstructExpr *CE,
       return MRMgr.getCXXTempObjectRegion(CE, LCtx);
     }
     case ConstructionContext::ReturnedValueKind: {
-      // TODO: We should construct into a CXXBindTemporaryExpr or a
-      // MaterializeTemporaryExpr around the call-expression on the previous
-      // stack frame. Currently we re-bind the temporary to the correct region
-      // later, but that's not semantically correct. This of course does not
-      // apply when we're in the top frame. But if we are in an inlined
-      // function, we should be able to take the call-site CFG element,
-      // and it should contain (but right now it wouldn't) some sort of
-      // construction context that'd give us the right temporary expression.
+      // The temporary is to be managed by the parent stack frame.
+      // So build it in the parent stack frame if we're not in the
+      // top frame of the analysis.
+      // TODO: What exactly happens when we are? Does the temporary object live
+      // long enough in the region store in this case? Would checkers think
+      // that this object immediately goes out of scope?
+      const LocationContext *TempLCtx = LCtx;
+      if (const LocationContext *CallerLCtx =
+              LCtx->getCurrentStackFrame()->getParent()) {
+        TempLCtx = CallerLCtx;
+      }
       CallOpts.IsTemporaryCtorOrDtor = true;
-      return MRMgr.getCXXTempObjectRegion(CE, LCtx);
+      return MRMgr.getCXXTempObjectRegion(CE, TempLCtx);
     }
     }
   }
@@ -262,6 +265,7 @@ void ExprEngine::VisitCXXConstructExpr(const CXXConstructExpr *CE,
   assert(C || getCurrentCFGElement().getAs<CFGStmt>());
   const ConstructionContext *CC = C ? C->getConstructionContext() : nullptr;
 
+  bool IsReturnedIntoParentStackFrame = false;
   const CXXBindTemporaryExpr *BTE = nullptr;
   const MaterializeTemporaryExpr *MTE = nullptr;
 
@@ -269,25 +273,44 @@ void ExprEngine::VisitCXXConstructExpr(const CXXConstructExpr *CE,
   case CXXConstructExpr::CK_Complete: {
     Target = getRegionForConstructedObject(CE, Pred, CC, CallOpts);
 
-    // In case of temporary object construction, extract data necessary for
-    // destruction and lifetime extension.
-    if (const auto *TCC =
-            dyn_cast_or_null<TemporaryObjectConstructionContext>(CC)) {
-      assert(CallOpts.IsTemporaryCtorOrDtor);
-      assert(!CallOpts.IsCtorOrDtorWithImproperlyModeledTargetRegion);
-      if (AMgr.getAnalyzerOptions().includeTemporaryDtorsInCFG()) {
-        BTE = TCC->getCXXBindTemporaryExpr();
-        MTE = TCC->getMaterializedTemporaryExpr();
-        if (!BTE) {
-          // FIXME: lifetime extension for temporaries without destructors
-          // is not implemented yet.
-          MTE = nullptr;
+    if (CC) {
+      // In case of temporary object construction, extract data necessary for
+      // destruction and lifetime extension.
+      const auto *TCC = dyn_cast<TemporaryObjectConstructionContext>(CC);
+
+      // If the temporary is being returned from the function, it will be
+      // destroyed or lifetime-extended in the caller stack frame.
+      if (const auto *RCC = dyn_cast<ReturnedValueConstructionContext>(CC)) {
+        const StackFrameContext *SFC = LCtx->getCurrentStackFrame();
+        assert(SFC);
+        if (SFC->getParent()) {
+          IsReturnedIntoParentStackFrame = true;
+          const CFGElement &CallElem =
+              (*SFC->getCallSiteBlock())[SFC->getIndex()];
+          if (auto RTCElem = CallElem.getAs<CFGCXXRecordTypedCall>()) {
+            TCC = cast<TemporaryObjectConstructionContext>(
+                RTCElem->getConstructionContext());
+          }
         }
-        if (MTE && MTE->getStorageDuration() != SD_FullExpression) {
-          // If the temporary is lifetime-extended, don't save the BTE,
-          // because we don't need a temporary destructor, but an automatic
-          // destructor.
-          BTE = nullptr;
+      }
+
+      if (TCC) {
+        assert(CallOpts.IsTemporaryCtorOrDtor);
+        assert(!CallOpts.IsCtorOrDtorWithImproperlyModeledTargetRegion);
+        if (AMgr.getAnalyzerOptions().includeTemporaryDtorsInCFG()) {
+          BTE = TCC->getCXXBindTemporaryExpr();
+          MTE = TCC->getMaterializedTemporaryExpr();
+          if (!BTE) {
+            // FIXME: lifetime extension for temporaries without destructors
+            // is not implemented yet.
+            MTE = nullptr;
+          }
+          if (MTE && MTE->getStorageDuration() != SD_FullExpression) {
+            // If the temporary is lifetime-extended, don't save the BTE,
+            // because we don't need a temporary destructor, but an automatic
+            // destructor.
+            BTE = nullptr;
+          }
         }
       }
     }
@@ -385,13 +408,19 @@ void ExprEngine::VisitCXXConstructExpr(const CXXConstructExpr *CE,
         State = State->bindDefault(loc::MemRegionVal(Target), ZeroVal, LCtx);
       }
 
+      // Set up destruction and lifetime extension information.
+      const LocationContext *TempLCtx =
+          IsReturnedIntoParentStackFrame
+              ? LCtx->getCurrentStackFrame()->getParent()
+              : LCtx;
+
       if (BTE) {
-        State = addInitializedTemporary(State, BTE, LCtx,
+        State = addInitializedTemporary(State, BTE, TempLCtx,
                                         cast<CXXTempObjectRegion>(Target));
       }
 
       if (MTE) {
-        State = addTemporaryMaterialization(State, MTE, LCtx,
+        State = addTemporaryMaterialization(State, MTE, TempLCtx,
                                             cast<CXXTempObjectRegion>(Target));
       }