From cb77930d6b20e53c735233eecf4572a1c30eb0c0 Mon Sep 17 00:00:00 2001
From: Yunzhong Gao <Yunzhong_Gao@playstation.sony.com>
Date: Wed, 10 Jun 2015 00:27:52 +0000
Subject: Implementing C99 partial re-initialization behavior (DR-253)

Based on previous discussion on the mailing list, clang currently lacks support
for C99 partial re-initialization behavior:
Reference: http://lists.cs.uiuc.edu/pipermail/cfe-dev/2013-April/029188.html
Reference: http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_253.htm

This patch attempts to fix this problem.

Given the following code snippet,

struct P1 { char x[6]; };
struct LP1 { struct P1 p1; };

struct LP1 l = { .p1 = { "foo" }, .p1.x[2] = 'x' };
// this example is adapted from the example for "struct fred x[]" in DR-253;
// currently clang produces in l: { "\0\0x" },
//   whereas gcc 4.8 produces { "fox" };
// with this fix, clang will also produce: { "fox" };


Differential Review: http://reviews.llvm.org/D5789

llvm-svn: 239446
---
 clang/lib/CodeGen/CGExprAgg.cpp | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'clang/lib/CodeGen/CGExprAgg.cpp')

diff --git a/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp
index 8b1bc69352b..883b76bcfab 100644
--- a/clang/lib/CodeGen/CGExprAgg.cpp
+++ b/clang/lib/CodeGen/CGExprAgg.cpp
@@ -160,10 +160,12 @@ public:
     EmitAggLoadOfLValue(E);
   }
 
+  void VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E);
   void VisitAbstractConditionalOperator(const AbstractConditionalOperator *CO);
   void VisitChooseExpr(const ChooseExpr *CE);
   void VisitInitListExpr(InitListExpr *E);
   void VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
+  void VisitNoInitExpr(NoInitExpr *E) { } // Do nothing.
   void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
     Visit(DAE->getExpr());
   }
@@ -1056,6 +1058,9 @@ AggExprEmitter::EmitInitializationToLValue(Expr *E, LValue LV) {
     return;
   } else if (isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) {
     return EmitNullInitializationToLValue(LV);
+  } else if (isa<NoInitExpr>(E)) {
+    // Do nothing.
+    return;
   } else if (type->isReferenceType()) {
     RValue RV = CGF.EmitReferenceBindingToExpr(E);
     return CGF.EmitStoreThroughLValue(RV, LV);
@@ -1276,6 +1281,15 @@ void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
     cleanupDominator->eraseFromParent();
 }
 
+void AggExprEmitter::VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E) {
+  AggValueSlot Dest = EnsureSlot(E->getType());
+
+  LValue DestLV = CGF.MakeAddrLValue(Dest.getAddr(), E->getType(),
+                                     Dest.getAlignment());
+  EmitInitializationToLValue(E->getBase(), DestLV);
+  VisitInitListExpr(E->getUpdater());
+}
+
 //===----------------------------------------------------------------------===//
 //                        Entry Points into this File
 //===----------------------------------------------------------------------===//
-- 
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