[clang] a603f56 - [clang] CWG 2354: prohibit alignas for enums
Chuanqi Xu via cfe-commits
cfe-commits at lists.llvm.org
Wed Mar 16 00:48:45 PDT 2022
Author: Vlad Serebrennikov
Date: 2022-03-16T15:48:18+08:00
New Revision: a603f566dbe04d8a9eb0ada67b585965945f7e6d
URL: https://github.com/llvm/llvm-project/commit/a603f566dbe04d8a9eb0ada67b585965945f7e6d
DIFF: https://github.com/llvm/llvm-project/commit/a603f566dbe04d8a9eb0ada67b585965945f7e6d.diff
LOG: [clang] CWG 2354: prohibit alignas for enums
Reviewed By: aaron.ballman, erichkeane
Differential Revision: https://reviews.llvm.org/D121723
Added:
clang/test/CXX/drs/dr2354.cpp
Modified:
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/Sema/SemaDeclAttr.cpp
clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp
clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p6.cpp
clang/www/cxx_dr_status.html
Removed:
################################################################################
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index e17b018937fb4..0806cc4170753 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3022,8 +3022,9 @@ def err_aligned_attribute_argument_not_int : Error<
def err_align_value_attribute_argument_not_int : Error<
"'align_value' attribute requires integer constant">;
def err_alignas_attribute_wrong_decl_type : Error<
- "%0 attribute cannot be applied to a %select{function parameter|"
- "variable with 'register' storage class|'catch' variable|bit-field}1">;
+ "%0 attribute cannot be applied to %select{a function parameter|"
+ "a variable with 'register' storage class|a 'catch' variable|a bit-field|"
+ "an enumeration}1">;
def err_alignas_missing_on_definition : Error<
"%0 must be specified on definition if it is specified on any declaration">;
def note_alignas_on_declaration : Note<"declared with %0 attribute here">;
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 3034abdf04028..70d6721a8b1c0 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -4290,6 +4290,9 @@ void Sema::AddAlignedAttr(Decl *D, const AttributeCommonInfo &CI, Expr *E,
// declared with the register storage class specifier. An
// alignment-specifier may also be applied to the declaration of a class
// or enumeration type.
+ // CWG 2354:
+ // CWG agreed to remove permission for alignas to be applied to
+ // enumerations.
// C11 6.7.5/2:
// An alignment attribute shall not be specified in a declaration of
// a typedef, or a bit-field, or a function, or a parameter, or an
@@ -4305,6 +4308,9 @@ void Sema::AddAlignedAttr(Decl *D, const AttributeCommonInfo &CI, Expr *E,
} else if (const auto *FD = dyn_cast<FieldDecl>(D)) {
if (FD->isBitField())
DiagKind = 3;
+ } else if (const auto *ED = dyn_cast<EnumDecl>(D)) {
+ if (ED->getLangOpts().CPlusPlus)
+ DiagKind = 4;
} else if (!isa<TagDecl>(D)) {
Diag(AttrLoc, diag::err_attribute_wrong_decl_type) << &TmpAttr
<< (TmpAttr.isC11() ? ExpectedVariableOrField
diff --git a/clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp b/clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp
index e713d72dc58fa..45d5ebf68ba8f 100644
--- a/clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp
+++ b/clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp
@@ -11,13 +11,6 @@ alignas(1) int n7 alignas(2), // expected-error {{less than minimum alignment}}
alignas(8) int n9 alignas(2); // ok, overaligned
alignas(1) extern int n10; // expected-error {{less than minimum alignment}}
-enum alignas(1) E1 {}; // expected-error {{requested alignment is less than minimum alignment of 4 for type 'E1'}}
-enum alignas(1) E2 : char {}; // ok
-enum alignas(4) E3 { e3 = 0 }; // ok
-enum alignas(4) E4 { e4 = 1ull << 33 }; // expected-error {{requested alignment is less than minimum alignment of 8 for type 'E4'}}
-enum alignas(8) E5 {};
-static_assert(alignof(E5) == 8, "");
-
typedef __attribute__((aligned(16))) int IntAlign16;
enum E6 : IntAlign16 {};
static_assert(alignof(E6) == 4, "");
@@ -62,15 +55,6 @@ template struct X<2, 2, short>;
template struct X<16, 8, S1>;
template struct X<4, 4, S1>; // expected-note {{instantiation}}
-template<int N, typename T>
-struct Y {
- enum alignas(N) E : T {}; // expected-error {{requested alignment is less than minimum}}
-};
-template struct Y<1, char>;
-template struct Y<2, char>;
-template struct Y<1, short>; // expected-note {{instantiation}}
-template struct Y<2, short>;
-
template<int N, typename T>
void f() {
alignas(N) T v; // expected-error {{requested alignment is less than minimum}}
diff --git a/clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p6.cpp b/clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p6.cpp
index e788577480770..5d93336341f6e 100644
--- a/clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p6.cpp
+++ b/clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p6.cpp
@@ -27,21 +27,6 @@ int n8; // expected-error {{'alignas' must be specified on definition if it is s
int n9; // expected-error {{'alignas' must be specified on definition if it is specified on any declaration}}
alignas(4) extern int n9; // expected-note {{declared with 'alignas' attribute here}}
-
-enum alignas(2) E : char; // expected-note {{declared with 'alignas' attribute here}}
-enum E : char {}; // expected-error {{'alignas' must be specified on definition if it is specified on any declaration}}
-
-enum alignas(4) F : char; // expected-note {{previous declaration is here}}
-enum alignas(2) F : char; // expected-error {{redeclaration has
diff erent alignment requirement (2 vs 4)}}
-
-enum G : char;
-enum alignas(8) G : char {};
-enum G : char;
-
-enum H : char {}; // expected-error {{'alignas' must be specified on definition if it is specified on any declaration}}
-enum alignas(1) H : char; // expected-note {{declared with 'alignas' attribute here}}
-
-
struct S;
struct alignas(16) S; // expected-note {{declared with 'alignas' attribute here}}
struct S;
@@ -73,14 +58,5 @@ alignas(O) alignas(P) char X<M, N, O, P>::Buffer[32]; // expected-error {{redecl
char *x1848 = X<1,8,4,8>::Buffer; // ok
char *x1248 = X<1,2,4,8>::Buffer; // expected-note {{in instantiation of}}
-template<int M, int N, int O, int P> struct Y {
- enum alignas(M) alignas(N) E : char;
-};
-template<int M, int N, int O, int P>
-enum alignas(O) alignas(P) Y<M,N,O,P>::E : char { e };
-int y1848 = Y<1,8,4,8>::e;
-// FIXME: We should reject this.
-int y1248 = Y<1,2,4,8>::e;
-
// Don't crash here.
alignas(4) struct Incomplete incomplete; // expected-error {{incomplete type}} expected-note {{forward declaration}}
diff --git a/clang/test/CXX/drs/dr2354.cpp b/clang/test/CXX/drs/dr2354.cpp
new file mode 100644
index 0000000000000..3efb0ba555669
--- /dev/null
+++ b/clang/test/CXX/drs/dr2354.cpp
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -x c++ -verify %s
+
+// dr2354: 15
+
+namespace DR2354 {
+
+enum alignas(64) A {}; // expected-error {{'alignas' attribute cannot be applied to an enumeration}}
+enum struct alignas(64) B {}; // expected-error {{'alignas' attribute cannot be applied to an enumeration}}
+
+} // namespace DR2354
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index 62ccfc518d456..4734e9fd89253 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -13938,7 +13938,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
<td><a href="https://wg21.link/cwg2354">2354</a></td>
<td>CD5</td>
<td>Extended alignment and object representation</td>
- <td class="none" align="center">Unknown</td>
+ <td class="unreleased" align="center">Clang 15</td>
</tr>
<tr class="open" id="2355">
<td><a href="https://wg21.link/cwg2355">2355</a></td>
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