PR20256: don't accidentally instantiate non-dependent default-initialization as

value-initialization.

llvm-svn: 212764

Author: zygoloid

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -3679,8 +3679,9 @@ void Sema::InstantiateVariableInitializer(
       bool TypeMayContainAuto = true;
       Expr *InitExpr = Init.get();
 
-      if (Var->hasAttr<DLLImportAttr>() && InitExpr &&
-          !InitExpr->isConstantInitializer(getASTContext(), false)) {
+      if (Var->hasAttr<DLLImportAttr>() &&
+          (!InitExpr ||
+           !InitExpr->isConstantInitializer(getASTContext(), false))) {
         // Do not dynamically initialize dllimport variables.
       } else if (InitExpr) {
         bool DirectInit = OldVar->isDirectInit();

clang/lib/Sema/TreeTransform.h

@@ -2891,6 +2891,13 @@ ExprResult TreeTransform<Derived>::TransformInitializer(Expr *Init,
 
   // Build a ParenListExpr to represent anything else.
   SourceRange Parens = Construct->getParenOrBraceRange();
+  if (Parens.isInvalid()) {
+    // This was a variable declaration's initialization for which no initializer
+    // was specified.
+    assert(NewArgs.empty() &&
+           "no parens or braces but have direct init with arguments?");
+    return ExprEmpty();
+  }
   return getDerived().RebuildParenListExpr(Parens.getBegin(), NewArgs,
                                            Parens.getEnd());
 }

clang/test/CodeGenCXX/value-init.cpp

@@ -262,6 +262,59 @@ namespace PR11124 {
 void r170806_a(bool b = bool());
 void r170806_b() { r170806_a(); }
 
+namespace PR20256 {
+  struct data { int i; };
+
+  template<typename T = int>
+  data g() {
+    data d; // not value-init
+    return d;
+  }
+  template data g();
+  // CHECK-LABEL: define {{.*}} @_ZN7PR202561gIiEENS_4dataEv(
+  // CHECK-NOT: store
+  // CHECK-NOT: memset
+  // CHECK: }
+
+  template<typename ...T>
+  data h(T ...t) {
+    data d(t...); // value-init
+    return d;
+  }
+  template data h();
+  // CHECK-LABEL: define {{.*}} @_ZN7PR202561hIJEEENS_4dataEDpT_(
+  // CHECK: call void @llvm.memset
+  // CHECK: }
+
+
+  template<typename T = int>
+  data j() {
+    data d = {}; // value-init
+    return d;
+  }
+  template data j();
+  // CHECK-LABEL: define {{.*}} @_ZN7PR202561jIiEENS_4dataEv(
+  // CHECK: call void @llvm.memset
+  // CHECK: }
+
+  data f() {
+    data d; // not value-init
+    return d;
+  }
+  // CHECK-LABEL: define {{.*}} @_ZN7PR202561fEv(
+  // CHECK-NOT: store
+  // CHECK-NOT: memset
+  // CHECK: }
+
+  data i() {
+    data d = {}; // value-init
+    return d;
+  }
+  // CHECK-LABEL: define {{.*}} @_ZN7PR202561iEv(
+  // CHECK: call void @llvm.memset
+  // CHECK: }
+}
+
 // CHECK-LABEL: define linkonce_odr void @_ZN8zeroinit2X3IiEC2Ev(%"struct.zeroinit::X3"* %this) unnamed_addr
 // CHECK: call void @llvm.memset.p0i8.i64
 // CHECK-NEXT: call void @_ZN8zeroinit2X2IiEC2Ev