[CFG] [analyzer] Avoid modeling C++17 constructors that aren't fully supported.

Not enough work has been done so far to ensure correctness of construction
contexts in the CFG when C++17 copy elision is in effect, so for now we
should drop construction contexts in the CFG and in the analyzer when
they seem different from what we support anyway.

This includes initializations with conditional operators and return values
across multiple stack frames.

Differential Revision: https://reviews.llvm.org/D44854

llvm-svn: 328893

1 files changed, 9 insertions, 0 deletions

diff --git a/clang/lib/Analysis/CFG.cpp b/clang/lib/Analysis/CFG.cpp
index 77770c56f31..0f0556135c2 100644
--- a/clang/lib/Analysis/CFG.cpp
+++ b/clang/lib/Analysis/CFG.cpp
@@ -1302,6 +1302,15 @@ void CFGBuilder::findConstructionContexts(
   }
   case Stmt::ConditionalOperatorClass: {
     auto *CO = cast<ConditionalOperator>(Child);
+    if (!dyn_cast_or_null<MaterializeTemporaryExpr>(Layer->getTriggerStmt())) {
+      // If the object returned by the conditional operator is not going to be a
+      // temporary object that needs to be immediately materialized, then
+      // it must be C++17 with its mandatory copy elision. Do not yet promise
+      // to support this case.
+      assert(!CO->getType()->getAsCXXRecordDecl() || CO->isGLValue() ||
+             Context->getLangOpts().CPlusPlus17);
+      break;
+    }
     findConstructionContexts(Layer, CO->getLHS());
     findConstructionContexts(Layer, CO->getRHS());
     break;