[analyzer] Support C++ default arguments if they are literal values.

A CXXDefaultArgExpr wraps an Expr owned by a ParmVarDecl belonging to the
called function. In general, ExprEngine and Environment ought to treat this
like a ParenExpr or other transparent wrapper expression, with the inside
expression evaluated first.

However, if we call the same function twice, we'd produce a CFG that contains
the same wrapped expression twice, and we're not set up to handle that. I've
added a FIXME to the CFG builder to come back to that, but meanwhile we can
at least handle expressions that don't need to be explicitly evaluated:
literals. This probably handles many common uses of default parameters:
true/false, null, etc.

Part of PR13385 / <rdar://problem/12156507>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@162453 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1 insertions, 5 deletions

diff --git a/lib/StaticAnalyzer/Core/ExprEngine.cpp b/lib/StaticAnalyzer/Core/ExprEngine.cpp
index a77a338b27..d9b7ff57bf 100644
--- a/lib/StaticAnalyzer/Core/ExprEngine.cpp
+++ b/lib/StaticAnalyzer/Core/ExprEngine.cpp
@@ -529,11 +529,6 @@ void ExprEngine::Visit(const Stmt *S, ExplodedNode *Pred,
       break;
     }
     
-    // We don't handle default arguments either yet, but we can fake it
-    // for now by just skipping them.
-    case Stmt::CXXDefaultArgExprClass:
-      break;
-
     case Stmt::ParenExprClass:
       llvm_unreachable("ParenExprs already handled.");
     case Stmt::GenericSelectionExprClass:
@@ -619,6 +614,7 @@ void ExprEngine::Visit(const Stmt *S, ExplodedNode *Pred,
     case Stmt::StringLiteralClass:
     case Stmt::ObjCStringLiteralClass:
     case Stmt::CXXBindTemporaryExprClass:
+    case Stmt::CXXDefaultArgExprClass:
     case Stmt::SubstNonTypeTemplateParmExprClass:
     case Stmt::CXXNullPtrLiteralExprClass: {
       Bldr.takeNodes(Pred);