[analyzer] Re-enable lifetime extension for temporaries without destructors.

When an object's class provides no destructor, it's less important to
materialize that object properly because we don't have to model the destructor
correctly, so previously we skipped the support for these syntax patterns.

Additionally, fix support for construction contexts of "static temporaries"
(temporaries that are lifetime-extended by static references) because
it turned out that we only had tests for them without destructors, which caused
us to regress when we re-introduced the construction context for such
temporaries.

Differential Revision: https://reviews.llvm.org/D47658

llvm-svn: 335796

1 files changed, 7 insertions, 9 deletions

diff --git a/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp b/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
index 497e1fa5560..2e8e14a7a0c 100644
--- a/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
+++ b/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
@@ -218,12 +218,6 @@ std::pair<ProgramStateRef, SVal> ExprEngine::prepareForObjectConstruction(
       const CXXBindTemporaryExpr *BTE = TCC->getCXXBindTemporaryExpr();
       const MaterializeTemporaryExpr *MTE = TCC->getMaterializedTemporaryExpr();
 
-      if (!BTE) {
-        // FIXME: Lifetime extension for temporaries without destructors
-        // is not implemented yet.
-        MTE = nullptr;
-      }
-
       if (MTE) {
         if (const ValueDecl *VD = MTE->getExtendingDecl()) {
           assert(MTE->getStorageDuration() != SD_FullExpression);
@@ -238,16 +232,20 @@ std::pair<ProgramStateRef, SVal> ExprEngine::prepareForObjectConstruction(
         }
       }
 
+      SVal V = UnknownVal();
       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 (MTE->getStorageDuration() == SD_Static ||
+            MTE->getStorageDuration() == SD_Thread)
+          V = loc::MemRegionVal(MRMgr.getCXXStaticTempObjectRegion(E));
       }
 
-      // FIXME: Support temporaries lifetime-extended via static references.
-      // They'd need a getCXXStaticTempObjectRegion().
-      SVal V = loc::MemRegionVal(MRMgr.getCXXTempObjectRegion(E, LCtx));
+      if (V.isUnknown())
+        V = loc::MemRegionVal(MRMgr.getCXXTempObjectRegion(E, LCtx));
 
       if (BTE)
         State = addObjectUnderConstruction(State, BTE, LCtx, V);