From: Anders Carlsson <andersca@mac.com>
Date: Mon, 3 May 2010 01:20:20 +0000 (+0000)
Subject: Don't copy or initialize empty classes. Fixes PR7012.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=0d7c583a4b4d0f57c6b69c66fd73babec4ef3799;p=clang

Don't copy or initialize empty classes. Fixes PR7012.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@102891 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CGExprAgg.cpp b/lib/CodeGen/CGExprAgg.cpp
index 84841bf5b9..96274cb6e7 100644
--- a/lib/CodeGen/CGExprAgg.cpp
+++ b/lib/CodeGen/CGExprAgg.cpp
@@ -738,6 +738,14 @@ void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
                                         bool isVolatile) {
   assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
 
+  // Ignore empty classes in C++.
+  if (getContext().getLangOptions().CPlusPlus) {
+    if (const RecordType *RT = Ty->getAs<RecordType>()) {
+      if (cast<CXXRecordDecl>(RT->getDecl())->isEmpty())
+        return;
+    }
+  }
+  
   // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
   // C99 6.5.16.1p3, which states "If the value being stored in an object is
   // read from another object that overlaps in anyway the storage of the first
diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp
index 34b904972f..d3bf1645a0 100644
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@@ -473,6 +473,14 @@ void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
 }
 
 void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty) {
+  // Ignore empty classes in C++.
+  if (getContext().getLangOptions().CPlusPlus) {
+    if (const RecordType *RT = Ty->getAs<RecordType>()) {
+      if (cast<CXXRecordDecl>(RT->getDecl())->isEmpty())
+        return;
+    }
+  }
+  
   const llvm::Type *BP = llvm::Type::getInt8PtrTy(VMContext);
   if (DestPtr->getType() != BP)
     DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
diff --git a/test/CodeGenCXX/new.cpp b/test/CodeGenCXX/new.cpp
index ca7c52f2cc..cc6288575b 100644
--- a/test/CodeGenCXX/new.cpp
+++ b/test/CodeGenCXX/new.cpp
@@ -90,7 +90,7 @@ A* t10() {
   return new(1, 2, 3.45, 100) A;
 }
 
-struct B { };
+struct B { int a; };
 void t11() {
   // CHECK: call noalias i8* @_Znwm
   // CHECK: call void @llvm.memset.p0i8.i64(