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DR1359: A constexpr constructor does not need to initialize an empty struct or 

empty union. This still rejects anonymous member structs or unions which only
contain such empty class types, pending standard wording defining exactly what
an empty class type is.

llvm-svn: 150157
This commit is contained in:
Richard Smith 2012-02-09 06:40:58 +00:00
parent 2b5bb97986
commit 4d59eebb49
2 changed files with 22 additions and 5 deletions
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15
clang/lib/Sema/SemaDeclCXX.cpp
View File

@ -816,6 +816,10 @@ static void CheckConstexprCtorInitializer(Sema &SemaRef,
if (Field->isUnnamedBitfield())
return;
if (Field->isAnonymousStructOrUnion() &&
Field->getType()->getAsCXXRecordDecl()->isEmpty())
return;
if (!Inits.count(Field)) {
if (!Diagnosed) {
SemaRef.Diag(Dcl->getLocation(), diag::err_constexpr_ctor_missing_init);
@ -901,11 +905,14 @@ bool Sema::CheckConstexprFunctionBody(const FunctionDecl *Dcl, Stmt *Body,
if (const CXXConstructorDecl *Constructor
= dyn_cast<CXXConstructorDecl>(Dcl)) {
const CXXRecordDecl *RD = Constructor->getParent();
// - every non-static data member and base class sub-object shall be
// initialized;
// DR1359:
// - every non-variant non-static data member and base class sub-object
// shall be initialized;
// - if the class is a non-empty union, or for each non-empty anonymous
// union member of a non-union class, exactly one non-static data member
// shall be initialized;
if (RD->isUnion()) {
// DR1359: Exactly one member of a union shall be initialized.
if (Constructor->getNumCtorInitializers() == 0) {
if (Constructor->getNumCtorInitializers() == 0 && !RD->isEmpty()) {
Diag(Dcl->getLocation(), diag::err_constexpr_union_ctor_no_init);
return false;
}

10
clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p4.cpp
View File

@ -151,6 +151,16 @@ struct AnonMembers {
constexpr AnonMembers(int(&)[6]) {} // expected-error {{constexpr constructor must initialize all members}}
};
union Empty {
constexpr Empty() {} // ok
} constexpr empty1;
struct EmptyVariant {
union {};
struct {};
constexpr EmptyVariant() {} // ok
} constexpr empty2;
template<typename T> using Int = int;
template<typename T>
struct TemplateInit {