Introduce a new expression node, ImplicitValueInitExpr, that

represents an implicit value-initialization of a subobject of a
particular type. This replaces the (ab)use of CXXZeroValueInitExpr
within initializer lists for the "holes" that occur due to the use of
C99 designated initializers.

The new test case is currently XFAIL'd, because CodeGen's
ConstExprEmitter (in lib/CodeGen/CGExprConstant.cpp) needs to be
taught to value-initialize when it sees ImplicitValueInitExprs.

llvm-svn: 63317

2 files changed, 25 insertions, 13 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 7572560be19..1559213fcb8 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -2220,17 +2220,17 @@ bool Sema::CheckForConstantInitializer(Expr *Init, QualType DclT) {
   if (CompoundLiteralExpr *e = dyn_cast<CompoundLiteralExpr>(Init))
     return CheckForConstantInitializer(e->getInitializer(), DclT);
 
+  if (isa<ImplicitValueInitExpr>(Init)) {
+    // FIXME: In C++, check for non-POD types.
+    return false;
+  }
+
   if (InitListExpr *Exp = dyn_cast<InitListExpr>(Init)) {
     unsigned numInits = Exp->getNumInits();
     for (unsigned i = 0; i < numInits; i++) {
       // FIXME: Need to get the type of the declaration for C++,
       // because it could be a reference?
 
-      // Implicitly-generated value initializations are okay.
-      if (isa<CXXZeroInitValueExpr>(Exp->getInit(i)) &&
-          cast<CXXZeroInitValueExpr>(Exp->getInit(i))->isImplicit()) 
-        continue;
-
       if (CheckForConstantInitializer(Exp->getInit(i),
                                       Exp->getInit(i)->getType()))
         return true;
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 527f965dc3f..5d7f705edb1 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -17,7 +17,6 @@
 #include "clang/Parse/Designator.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Expr.h"
-#include "clang/AST/ExprCXX.h"
 #include <map>
 using namespace clang;
 
@@ -137,10 +136,9 @@ static void fillInValueInitializations(ASTContext &Context, InitListExpr *ILE) {
       // FIXME: Check for fields with reference type in C++?
       if (!ILE->getInit(Init))
         ILE->setInit(Init, 
-                     new (Context) CXXZeroInitValueExpr(Field->getType(), 
-                                                        SourceLocation(),
-                                                        SourceLocation()));
-      else if (InitListExpr *InnerILE = dyn_cast<InitListExpr>(ILE->getInit(Init)))
+                     new (Context) ImplicitValueInitExpr(Field->getType()));
+      else if (InitListExpr *InnerILE 
+                 = dyn_cast<InitListExpr>(ILE->getInit(Init)))
         fillInValueInitializations(Context, InnerILE);
       ++Init;
     }
@@ -160,9 +158,7 @@ static void fillInValueInitializations(ASTContext &Context, InitListExpr *ILE) {
   for (unsigned Init = 0, NumInits = ILE->getNumInits(); Init != NumInits; 
        ++Init) {
     if (!ILE->getInit(Init))
-      ILE->setInit(Init, new (Context) CXXZeroInitValueExpr(ElementType, 
-                                                            SourceLocation(),
-                                                            SourceLocation()));
+      ILE->setInit(Init, new (Context) ImplicitValueInitExpr(ElementType));
     else if (InitListExpr *InnerILE =dyn_cast<InitListExpr>(ILE->getInit(Init)))
       fillInValueInitializations(Context, InnerILE);
   }
@@ -550,6 +546,22 @@ void InitListChecker::CheckStructUnionTypes(InitListExpr *IList,
     hadError = true;
     return;
   }    
+
+  if (DeclType->isUnionType() && IList->getNumInits() == 0) {
+    // Value-initialize the first named member of the union.
+    RecordDecl *RD = DeclType->getAsRecordType()->getDecl();
+    for (RecordDecl::field_iterator FieldEnd = RD->field_end();
+         Field != FieldEnd; ++Field) {
+      if (Field->getDeclName()) {
+        StructuredList->setInitializedFieldInUnion(*Field);
+        break;
+      }
+    }
+    return;
+  }
+
+
+
   // If structDecl is a forward declaration, this loop won't do
   // anything except look at designated initializers; That's okay,
   // because an error should get printed out elsewhere. It might be