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Ensure that the "value" of an unnamed bit-field isn't taken into 

account when determining the identity of a class NTTP.
This commit is contained in:
Richard Smith 2020-10-21 18:50:43 -07:00
parent 716338a09a
commit 8156074352
2 changed files with 20 additions and 1 deletions
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2
clang/lib/AST/ExprConstant.cpp
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@ -9607,7 +9607,7 @@ static bool HandleClassZeroInitialization(EvalInfo &Info, const Expr *E,
for (const auto *I : RD->fields()) {
// -- if T is a reference type, no initialization is performed.
if (I->getType()->isReferenceType())
if (I->isUnnamedBitfield() || I->getType()->isReferenceType())
continue;
LValue Subobject = This;

19
clang/test/SemaTemplate/temp_arg_nontype_cxx20.cpp
View File

@ -201,3 +201,22 @@ namespace CTADPartialOrder {
template<typename T, A<0> a> struct X<T, T, a> { static constexpr int n = 4; };
static_assert(X<float, float, a>::n == 4);
}
namespace UnnamedBitfield {
struct A {
int : 16;
};
// Make sure we don't distinguish between the unnamed bit-field being
// uninitialized and it being zeroed. Those are not distinct states
// according to [temp.type]p2.
//
// FIXME: We shouldn't track a value for unnamed bit-fields, nor number
// them when computing field indexes.
template <A> struct X {};
constexpr A a;
using T = X<a>;
using T = X<A{}>;
using T = X<(A())>;
// Once we support bit-casts involving bit-fields, this should be valid too.
using T = X<__builtin_bit_cast(A, (unsigned short)0)>; // expected-error {{constant}} expected-note {{not yet supported}}
}