leoetlino created this revision.
leoetlino requested review of this revision.
Herald added a project: clang.
C++17 changed the definition of literal types so that unions that
have at least one non-static data member of non-volatile literal type
are also considered literal types.
This patch implements that new rule and also adds a test for closure
types (10.5.2) and for unions (10.5.3) to the existing test file for
literal types.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D113694
Files:
clang/include/clang/AST/CXXRecordDeclDefinitionBits.def
clang/include/clang/AST/DeclCXX.h
clang/lib/AST/DeclCXX.cpp
clang/test/CXX/basic/basic.types/p10.cpp
Index: clang/test/CXX/basic/basic.types/p10.cpp
===================================================================
--- clang/test/CXX/basic/basic.types/p10.cpp
+++ clang/test/CXX/basic/basic.types/p10.cpp
@@ -1,5 +1,6 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++1y %s -DCXX1Y
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s -DCXX11 -DCXX11_OR_LATER
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++1y %s -DCXX1Y -DCXX11_OR_LATER -DCXX1Y_OR_LATER
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++17 %s -DCXX17 -DCXX11_OR_LATER -DCXX1Y_OR_LATER -DCXX17_OR_LATER
struct NonLiteral { NonLiteral(); };
@@ -7,7 +8,7 @@
// [C++1y] - void
constexpr void f() {}
-#ifndef CXX1Y
+#ifdef CXX11
// expected-error@-2 {{'void' is not a literal type}}
#endif
@@ -20,7 +21,7 @@
struct BeingDefined;
extern BeingDefined beingdefined;
-struct BeingDefined {
+struct BeingDefined {
static constexpr BeingDefined& t = beingdefined;
};
@@ -64,8 +65,14 @@
};
constexpr int f(TrivDefaultedDtor) { return 0; }
-// - it is an aggregate type or has at least one constexpr constructor or
+// - it is [a closure type [C++17]], an aggregate type or has at least one constexpr constructor or
// constexpr constructor template that is not a copy or move constructor
+#ifndef CXX17_OR_LATER
+// expected-error@+4 {{not a literal type}}
+// expected-note@+2 {{lambda closure types are non-literal types before C++17}}
+#endif
+auto closure = [] {};
+constexpr int f(decltype(closure)) { return 0; }
struct Agg {
int a;
char *b;
@@ -101,7 +108,8 @@
template<typename T> constexpr DerivedFromVBase<T>::DerivedFromVBase() : T() {}
constexpr int nVBase = (DerivedFromVBase<HasVBase>(), 0); // expected-error {{constant expression}} expected-note {{cannot construct object of type 'DerivedFromVBase<HasVBase>' with virtual base class in a constant expression}}
-// - it has all non-static data members and base classes of literal types
+// - [C++17] if it is a union, at least one of its non-static data members is of non-volatile literal type, and
+// - [if it is not a union [C++17]] it has all non-static data members and base classes of literal types
struct NonLitMember {
S s; // expected-note {{has data member 's' of non-literal type 'S'}}
};
@@ -122,6 +130,19 @@
constexpr int f(MemberType<int>) { return 0; }
constexpr int f(MemberType<NonLiteral>) { return 0; } // expected-error {{not a literal type}}
+template<typename T>
+union UnionType {
+ char c;
+ T t;
+ constexpr UnionType() : c{} {}
+};
+constexpr int f(UnionType<int>) { return 0; }
+#ifndef CXX17_OR_LATER
+// expected-error@+3 {{not a literal type}}
+// expected-note@-6 {{'UnionType<NonLiteral>' is not literal because it has data member 't' of non-literal type 'NonLiteral'}}
+#endif
+constexpr int f(UnionType<NonLiteral>) { return 0; }
+
// - an array of literal type [C++1y] other than an array of runtime bound
struct ArrGood {
Agg agg[24];
Index: clang/lib/AST/DeclCXX.cpp
===================================================================
--- clang/lib/AST/DeclCXX.cpp
+++ clang/lib/AST/DeclCXX.cpp
@@ -102,7 +102,8 @@
DefaultedDefaultConstructorIsConstexpr(true),
HasConstexprDefaultConstructor(false),
DefaultedDestructorIsConstexpr(true),
- HasNonLiteralTypeFieldsOrBases(false), StructuralIfLiteral(true),
+ HasNonLiteralTypeFieldsOrBases(false),
+ HasNonVolatileLiteralTypeFields(false), StructuralIfLiteral(true),
UserProvidedDefaultConstructor(false), DeclaredSpecialMembers(0),
ImplicitCopyConstructorCanHaveConstParamForVBase(true),
ImplicitCopyConstructorCanHaveConstParamForNonVBase(true),
@@ -1103,8 +1104,12 @@
}
}
+ const bool IsNonVolatileLiteralTypeField =
+ T->isLiteralType(Context) && !T.isVolatileQualified();
// Record if this field is the first non-literal or volatile field or base.
- if (!T->isLiteralType(Context) || T.isVolatileQualified())
+ if (IsNonVolatileLiteralTypeField)
+ data().HasNonVolatileLiteralTypeFields = true;
+ else
data().HasNonLiteralTypeFieldsOrBases = true;
if (Field->hasInClassInitializer() ||
Index: clang/include/clang/AST/DeclCXX.h
===================================================================
--- clang/include/clang/AST/DeclCXX.h
+++ clang/include/clang/AST/DeclCXX.h
@@ -1354,6 +1354,12 @@
return data().HasNonLiteralTypeFieldsOrBases;
}
+ /// Determine whether this class has a non-volatile literal type
+ /// non-static data member.
+ bool hasNonVolatileLiteralTypeFields() const {
+ return data().HasNonVolatileLiteralTypeFields;
+ }
+
/// Determine whether this class has a using-declaration that names
/// a user-declared base class constructor.
bool hasInheritedConstructor() const {
@@ -1396,12 +1402,20 @@
/// treating types with trivial default constructors as literal types.
///
/// Only in C++17 and beyond, are lambdas literal types.
+ /// A union is a literal type if at least one of its non-static data members
+ /// is of non-volatile literal type.
bool isLiteral() const {
const LangOptions &LangOpts = getLangOpts();
+
+ bool FieldsOk = !hasNonLiteralTypeFieldsOrBases();
+ if (LangOpts.CPlusPlus17 && isUnion()) {
+ FieldsOk = field_empty() || hasNonVolatileLiteralTypeFields();
+ }
+
return (LangOpts.CPlusPlus20 ? hasConstexprDestructor()
: hasTrivialDestructor()) &&
(!isLambda() || LangOpts.CPlusPlus17) &&
- !hasNonLiteralTypeFieldsOrBases() &&
+ FieldsOk &&
(isAggregate() || isLambda() ||
hasConstexprNonCopyMoveConstructor() ||
hasTrivialDefaultConstructor());
Index: clang/include/clang/AST/CXXRecordDeclDefinitionBits.def
===================================================================
--- clang/include/clang/AST/CXXRecordDeclDefinitionBits.def
+++ clang/include/clang/AST/CXXRecordDeclDefinitionBits.def
@@ -214,6 +214,10 @@
/// member or base class of non-literal or volatile type.
FIELD(HasNonLiteralTypeFieldsOrBases, 1, NO_MERGE)
+/// True when this class contains at least one non-static data
+/// member of non-volatile literal type.
+FIELD(HasNonVolatileLiteralTypeFields, 1, NO_MERGE)
+
/// True if this class is a structural type, assuming it is a literal type.
FIELD(StructuralIfLiteral, 1, NO_MERGE)
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