[clang] CWG 2354: prohibit alignas for enums
Reviewed By: aaron.ballman, erichkeane Differential Revision: https://reviews.llvm.org/D121723
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@ -3022,8 +3022,9 @@ def err_aligned_attribute_argument_not_int : Error<
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def err_align_value_attribute_argument_not_int : Error<
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"'align_value' attribute requires integer constant">;
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def err_alignas_attribute_wrong_decl_type : Error<
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"%0 attribute cannot be applied to a %select{function parameter|"
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"variable with 'register' storage class|'catch' variable|bit-field}1">;
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"%0 attribute cannot be applied to %select{a function parameter|"
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"a variable with 'register' storage class|a 'catch' variable|a bit-field|"
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"an enumeration}1">;
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def err_alignas_missing_on_definition : Error<
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"%0 must be specified on definition if it is specified on any declaration">;
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def note_alignas_on_declaration : Note<"declared with %0 attribute here">;
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@ -4290,6 +4290,9 @@ void Sema::AddAlignedAttr(Decl *D, const AttributeCommonInfo &CI, Expr *E,
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// declared with the register storage class specifier. An
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// alignment-specifier may also be applied to the declaration of a class
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// or enumeration type.
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// CWG 2354:
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// CWG agreed to remove permission for alignas to be applied to
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// enumerations.
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// C11 6.7.5/2:
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// An alignment attribute shall not be specified in a declaration of
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// a typedef, or a bit-field, or a function, or a parameter, or an
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@ -4305,6 +4308,9 @@ void Sema::AddAlignedAttr(Decl *D, const AttributeCommonInfo &CI, Expr *E,
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} else if (const auto *FD = dyn_cast<FieldDecl>(D)) {
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if (FD->isBitField())
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DiagKind = 3;
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} else if (const auto *ED = dyn_cast<EnumDecl>(D)) {
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if (ED->getLangOpts().CPlusPlus)
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DiagKind = 4;
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} else if (!isa<TagDecl>(D)) {
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Diag(AttrLoc, diag::err_attribute_wrong_decl_type) << &TmpAttr
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<< (TmpAttr.isC11() ? ExpectedVariableOrField
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@ -11,13 +11,6 @@ alignas(1) int n7 alignas(2), // expected-error {{less than minimum alignment}}
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alignas(8) int n9 alignas(2); // ok, overaligned
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alignas(1) extern int n10; // expected-error {{less than minimum alignment}}
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enum alignas(1) E1 {}; // expected-error {{requested alignment is less than minimum alignment of 4 for type 'E1'}}
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enum alignas(1) E2 : char {}; // ok
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enum alignas(4) E3 { e3 = 0 }; // ok
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enum alignas(4) E4 { e4 = 1ull << 33 }; // expected-error {{requested alignment is less than minimum alignment of 8 for type 'E4'}}
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enum alignas(8) E5 {};
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static_assert(alignof(E5) == 8, "");
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typedef __attribute__((aligned(16))) int IntAlign16;
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enum E6 : IntAlign16 {};
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static_assert(alignof(E6) == 4, "");
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@ -62,15 +55,6 @@ template struct X<2, 2, short>;
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template struct X<16, 8, S1>;
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template struct X<4, 4, S1>; // expected-note {{instantiation}}
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template<int N, typename T>
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struct Y {
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enum alignas(N) E : T {}; // expected-error {{requested alignment is less than minimum}}
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};
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template struct Y<1, char>;
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template struct Y<2, char>;
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template struct Y<1, short>; // expected-note {{instantiation}}
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template struct Y<2, short>;
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template<int N, typename T>
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void f() {
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alignas(N) T v; // expected-error {{requested alignment is less than minimum}}
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@ -27,21 +27,6 @@ int n8; // expected-error {{'alignas' must be specified on definition if it is s
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int n9; // expected-error {{'alignas' must be specified on definition if it is specified on any declaration}}
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alignas(4) extern int n9; // expected-note {{declared with 'alignas' attribute here}}
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enum alignas(2) E : char; // expected-note {{declared with 'alignas' attribute here}}
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enum E : char {}; // expected-error {{'alignas' must be specified on definition if it is specified on any declaration}}
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enum alignas(4) F : char; // expected-note {{previous declaration is here}}
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enum alignas(2) F : char; // expected-error {{redeclaration has different alignment requirement (2 vs 4)}}
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enum G : char;
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enum alignas(8) G : char {};
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enum G : char;
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enum H : char {}; // expected-error {{'alignas' must be specified on definition if it is specified on any declaration}}
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enum alignas(1) H : char; // expected-note {{declared with 'alignas' attribute here}}
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struct S;
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struct alignas(16) S; // expected-note {{declared with 'alignas' attribute here}}
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struct S;
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@ -73,14 +58,5 @@ alignas(O) alignas(P) char X<M, N, O, P>::Buffer[32]; // expected-error {{redecl
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char *x1848 = X<1,8,4,8>::Buffer; // ok
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char *x1248 = X<1,2,4,8>::Buffer; // expected-note {{in instantiation of}}
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template<int M, int N, int O, int P> struct Y {
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enum alignas(M) alignas(N) E : char;
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};
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template<int M, int N, int O, int P>
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enum alignas(O) alignas(P) Y<M,N,O,P>::E : char { e };
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int y1848 = Y<1,8,4,8>::e;
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// FIXME: We should reject this.
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int y1248 = Y<1,2,4,8>::e;
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// Don't crash here.
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alignas(4) struct Incomplete incomplete; // expected-error {{incomplete type}} expected-note {{forward declaration}}
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10
clang/test/CXX/drs/dr2354.cpp
Normal file
10
clang/test/CXX/drs/dr2354.cpp
Normal file
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@ -0,0 +1,10 @@
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// RUN: %clang_cc1 -x c++ -verify %s
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// dr2354: 15
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namespace DR2354 {
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enum alignas(64) A {}; // expected-error {{'alignas' attribute cannot be applied to an enumeration}}
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enum struct alignas(64) B {}; // expected-error {{'alignas' attribute cannot be applied to an enumeration}}
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} // namespace DR2354
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@ -13938,7 +13938,7 @@ and <I>POD class</I></td>
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<td><a href="https://wg21.link/cwg2354">2354</a></td>
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<td>CD5</td>
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<td>Extended alignment and object representation</td>
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<td class="none" align="center">Unknown</td>
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<td class="unreleased" align="center">Clang 15</td>
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</tr>
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<tr class="open" id="2355">
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<td><a href="https://wg21.link/cwg2355">2355</a></td>
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