https://github.com/ojhunt updated
https://github.com/llvm/llvm-project/pull/117428
>From 3e25d7ef2e223942298078dace8979905956d05c Mon Sep 17 00:00:00 2001
From: Oliver Hunt <oli...@apple.com>
Date: Fri, 22 Nov 2024 17:53:24 +0100
Subject: [PATCH 1/4] Add an off-by-default warning to complain about MSVC
bitfield padding
---
clang/include/clang/Basic/DiagnosticGroups.td | 1 +
.../clang/Basic/DiagnosticSemaKinds.td | 6 +
clang/lib/Sema/SemaDecl.cpp | 27 ++-
.../SemaCXX/ms_struct-bitfield-padding.cpp | 180 ++++++++++++++++++
4 files changed, 212 insertions(+), 2 deletions(-)
create mode 100644 clang/test/SemaCXX/ms_struct-bitfield-padding.cpp
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td
b/clang/include/clang/Basic/DiagnosticGroups.td
index df9bf94b5d0398..57bdda4b8f8b47 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -631,6 +631,7 @@ def Packed : DiagGroup<"packed", [PackedNonPod]>;
def PaddedBitField : DiagGroup<"padded-bitfield">;
def Padded : DiagGroup<"padded", [PaddedBitField]>;
def UnalignedAccess : DiagGroup<"unaligned-access">;
+def MSBitfieldCompatibility : DiagGroup<"ms-bitfield-packing-compatibility">;
def PessimizingMove : DiagGroup<"pessimizing-move">;
def ReturnStdMove : DiagGroup<"return-std-move">;
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index eb05a6a77978af..aa13e3438d3739 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -6418,6 +6418,12 @@ def warn_signed_bitfield_enum_conversion : Warning<
InGroup<BitFieldEnumConversion>, DefaultIgnore;
def note_change_bitfield_sign : Note<
"consider making the bitfield type %select{unsigned|signed}0">;
+def warn_ms_bitfield_mismatched_storage_packing : Warning<
+ "bit-field %0 of type %1 has a different storage size (%2 vs %3 bytes) than
the "
+ "preceding bit-field and may not be packed under MSVC ABI">,
+ InGroup<MSBitfieldCompatibility>, DefaultIgnore;
+def note_ms_bitfield_mismatched_storage_size_previous : Note<
+ "preceding bit-field %0 declared here with type %1">;
def warn_missing_braces : Warning<
"suggest braces around initialization of subobject">,
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 74b0e5ad23bd48..18aeca3b34f659 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -19001,9 +19001,9 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc,
Decl *EnclosingDecl,
// Verify that all the fields are okay.
SmallVector<FieldDecl*, 32> RecFields;
-
+ std::optional<const FieldDecl *> PreviousField;
for (ArrayRef<Decl *>::iterator i = Fields.begin(), end = Fields.end();
- i != end; ++i) {
+ i != end; PreviousField = cast<FieldDecl>(*i), ++i) {
FieldDecl *FD = cast<FieldDecl>(*i);
// Get the type for the field.
@@ -19213,6 +19213,29 @@ void Sema::ActOnFields(Scope *S, SourceLocation
RecLoc, Decl *EnclosingDecl,
if (Record && FD->getType().isVolatileQualified())
Record->setHasVolatileMember(true);
+ auto IsNonDependentBitField = [](const FieldDecl *FD) {
+ if (!FD->isBitField())
+ return false;
+ if (FD->getType()->isDependentType())
+ return false;
+ return true;
+ };
+
+ if (Record && PreviousField && IsNonDependentBitField(FD) &&
+ IsNonDependentBitField(*PreviousField)) {
+ unsigned FDStorageSize =
+ Context.getTypeSizeInChars(FD->getType()).getQuantity();
+ unsigned PreviousFieldStorageSize =
+
Context.getTypeSizeInChars((*PreviousField)->getType()).getQuantity();
+ if (FDStorageSize != PreviousFieldStorageSize) {
+ Diag(FD->getLocation(),
+ diag::warn_ms_bitfield_mismatched_storage_packing)
+ << FD << FD->getType() << FDStorageSize <<
PreviousFieldStorageSize;
+ Diag((*PreviousField)->getLocation(),
+ diag::note_ms_bitfield_mismatched_storage_size_previous)
+ << *PreviousField << (*PreviousField)->getType();
+ }
+ }
// Keep track of the number of named members.
if (FD->getIdentifier())
++NumNamedMembers;
diff --git a/clang/test/SemaCXX/ms_struct-bitfield-padding.cpp
b/clang/test/SemaCXX/ms_struct-bitfield-padding.cpp
new file mode 100644
index 00000000000000..001086de5bbd10
--- /dev/null
+++ b/clang/test/SemaCXX/ms_struct-bitfield-padding.cpp
@@ -0,0 +1,180 @@
+
+// RUN: %clang_cc1 -fsyntax-only -Wms-bitfield-packing-compatibility -verify
-triple armv8 -std=c++23 %s
+// RUN: %clang_cc1 -fsyntax-only -DMS_BITFIELDS -mms-bitfields
-verify=msbitfields -triple armv8-apple-macos10.15 -std=c++23 %s
+
+// msbitfields-no-diagnostics
+
+enum Enum1 { Enum1_A, Enum1_B };
+enum Enum2 { Enum2_A, Enum2_B };
+
+enum class EnumU32_1 : unsigned { A, B };
+enum class EnumU32_2 : unsigned { A, B };
+enum class EnumU64 : unsigned long long { A, B };
+enum class EnumI32 : int { A, B };
+enum class EnumU8 : unsigned char { A, B };
+enum class EnumI8 : char { A, B };
+enum class EnumU16 : unsigned short { A, B };
+enum class EnumI16 : short { A, B };
+
+struct A {
+ unsigned int a : 15;
+ unsigned int b : 15;
+};
+static_assert(sizeof(A) == 4);
+
+struct B {
+ unsigned int a : 15;
+ int b : 15;
+};
+static_assert(sizeof(B) == 4);
+
+struct C {
+ unsigned int a : 15;
+ int b : 15;
+};
+static_assert(sizeof(C) == 4);
+
+struct D {
+ Enum1 a : 15;
+ Enum1 b : 15;
+};
+static_assert(sizeof(D) == 4);
+
+struct E {
+ Enum1 a : 15;
+ Enum2 b : 15;
+};
+static_assert(sizeof(E) == 4);
+
+struct F {
+ EnumU32_1 a : 15;
+ EnumU32_2 b : 15;
+};
+static_assert(sizeof(F) == 4);
+
+struct G {
+ EnumU32_1 a : 15;
+ EnumU64 b : 15;
+ // expected-warning@-1 {{bit-field 'b' of type 'EnumU64' has a different
storage size (8 vs 4 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-note@-3 {{preceding bit-field 'a' declared here with type
'EnumU32_1'}}
+};
+
+#ifdef MS_BITFIELDS
+ static_assert(sizeof(G) == 16);
+#else
+ static_assert(sizeof(G) == 8);
+#endif
+
+struct H {
+ EnumU32_1 a : 10;
+ EnumI32 b : 10;
+ EnumU32_1 c : 10;
+};
+static_assert(sizeof(H) == 4);
+
+struct I {
+ EnumU8 a : 3;
+ EnumI8 b : 5;
+ EnumU32_1 c : 10;
+ // expected-warning@-1 {{bit-field 'c' of type 'EnumU32_1' has a different
storage size (4 vs 1 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-note@-3 {{preceding bit-field 'b' declared here with type
'EnumI8'}}
+};
+#ifdef MS_BITFIELDS
+static_assert(sizeof(I) == 8);
+#else
+static_assert(sizeof(I) == 4);
+#endif
+
+struct J {
+ EnumU8 : 0;
+ EnumU8 b : 4;
+};
+static_assert(sizeof(J) == 1);
+
+struct K {
+ EnumU8 a : 4;
+ EnumU8 : 0;
+};
+static_assert(sizeof(K) == 1);
+
+struct L {
+ EnumU32_1 a : 10;
+ EnumU32_2 b : 10;
+ EnumU32_1 c : 10;
+};
+
+static_assert(sizeof(L) == 4);
+
+struct M {
+ EnumU32_1 a : 10;
+ EnumI32 b : 10;
+ EnumU32_1 c : 10;
+};
+
+static_assert(sizeof(M) == 4);
+
+struct N {
+ EnumU32_1 a : 10;
+ EnumU64 b : 10;
+ // expected-warning@-1 {{bit-field 'b' of type 'EnumU64' has a different
storage size (8 vs 4 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-note@-3 {{preceding bit-field 'a' declared here with type
'EnumU32_1'}}
+ EnumU32_1 c : 10;
+ // expected-warning@-1 {{bit-field 'c' of type 'EnumU32_1' has a different
storage size (4 vs 8 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-note@-5 {{preceding bit-field 'b' declared here with type
'EnumU64'}}
+};
+
+#ifdef MS_BITFIELDS
+static_assert(sizeof(N) == 24);
+#else
+static_assert(sizeof(N) == 8);
+#endif
+
+struct O {
+ EnumU16 a : 10;
+ EnumU32_1 b : 10;
+ // expected-warning@-1 {{bit-field 'b' of type 'EnumU32_1' has a different
storage size (4 vs 2 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-note@-3 {{preceding bit-field 'a' declared here with type
'EnumU16'}}
+};
+#ifdef MS_BITFIELDS
+static_assert(sizeof(O) == 8);
+#else
+static_assert(sizeof(O) == 4);
+#endif
+
+struct P {
+ EnumU32_1 a : 10;
+ EnumU16 b : 10;
+ // expected-warning@-1 {{bit-field 'b' of type 'EnumU16' has a different
storage size (2 vs 4 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-note@-3 {{preceding bit-field 'a' declared here with type
'EnumU32_1'}}
+};
+#ifdef MS_BITFIELDS
+static_assert(sizeof(P) == 8);
+#else
+static_assert(sizeof(P) == 4);
+#endif
+
+struct Q {
+ EnumU8 a : 6;
+ EnumU16 b : 6;
+ // expected-warning@-1 {{bit-field 'b' of type 'EnumU16' has a different
storage size (2 vs 1 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-note@-3 {{preceding bit-field 'a' declared here with type
'EnumU8'}}
+};
+#ifdef MS_BITFIELDS
+static_assert(sizeof(Q) == 4);
+#else
+static_assert(sizeof(Q) == 2);
+#endif
+
+struct R {
+ EnumU16 a : 9;
+ EnumU16 b : 9;
+ EnumU8 c : 6;
+ // expected-warning@-1 {{bit-field 'c' of type 'EnumU8' has a different
storage size (1 vs 2 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-note@-3 {{preceding bit-field 'b' declared here with type
'EnumU16'}}
+};
+
+#ifdef MS_BITFIELDS
+static_assert(sizeof(R) == 6);
+#else
+static_assert(sizeof(R) == 4);
+#endif
>From 11447fea7197a0902c0b1c23071b35de3b782f13 Mon Sep 17 00:00:00 2001
From: Oliver Hunt <oli...@apple.com>
Date: Sat, 30 Nov 2024 19:36:33 -0800
Subject: [PATCH 2/4] Address feedback
---
.../clang/Basic/DiagnosticSemaKinds.td | 5 ++--
clang/lib/Sema/SemaDecl.cpp | 24 ++++++++-----------
.../SemaCXX/ms_struct-bitfield-padding.cpp | 16 ++++++-------
3 files changed, 21 insertions(+), 24 deletions(-)
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 98ed070e398a50..ce4f68bbb8bfc0 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -6423,8 +6423,9 @@ def warn_signed_bitfield_enum_conversion : Warning<
def note_change_bitfield_sign : Note<
"consider making the bit-field type %select{unsigned|signed}0">;
def warn_ms_bitfield_mismatched_storage_packing : Warning<
- "bit-field %0 of type %1 has a different storage size (%2 vs %3 bytes) than
the "
- "preceding bit-field and may not be packed under MSVC ABI">,
+ "bit-field %0 of type %1 has a different storage size than the "
+ "preceding bit-field (%2 vs %3 bytes) and will not be packed under "
+ "the MSVC ABI">,
InGroup<MSBitfieldCompatibility>, DefaultIgnore;
def note_ms_bitfield_mismatched_storage_size_previous : Note<
"preceding bit-field %0 declared here with type %1">;
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 123e061404add0..a71c31b0a5ae36 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -19016,7 +19016,7 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc,
Decl *EnclosingDecl,
// Verify that all the fields are okay.
SmallVector<FieldDecl*, 32> RecFields;
- std::optional<const FieldDecl *> PreviousField;
+ const FieldDecl *PreviousField = nullptr;
for (ArrayRef<Decl *>::iterator i = Fields.begin(), end = Fields.end();
i != end; PreviousField = cast<FieldDecl>(*i), ++i) {
FieldDecl *FD = cast<FieldDecl>(*i);
@@ -19229,26 +19229,22 @@ void Sema::ActOnFields(Scope *S, SourceLocation
RecLoc, Decl *EnclosingDecl,
if (Record && FD->getType().isVolatileQualified())
Record->setHasVolatileMember(true);
auto IsNonDependentBitField = [](const FieldDecl *FD) {
- if (!FD->isBitField())
- return false;
- if (FD->getType()->isDependentType())
- return false;
- return true;
+ return FD->isBitField() && !FD->getType()->isDependentType();
};
if (Record && PreviousField && IsNonDependentBitField(FD) &&
- IsNonDependentBitField(*PreviousField)) {
- unsigned FDStorageSize =
- Context.getTypeSizeInChars(FD->getType()).getQuantity();
- unsigned PreviousFieldStorageSize =
-
Context.getTypeSizeInChars((*PreviousField)->getType()).getQuantity();
+ IsNonDependentBitField(PreviousField)) {
+ CharUnits FDStorageSize = Context.getTypeSizeInChars(FD->getType());
+ CharUnits PreviousFieldStorageSize =
+ Context.getTypeSizeInChars(PreviousField->getType());
if (FDStorageSize != PreviousFieldStorageSize) {
Diag(FD->getLocation(),
diag::warn_ms_bitfield_mismatched_storage_packing)
- << FD << FD->getType() << FDStorageSize <<
PreviousFieldStorageSize;
- Diag((*PreviousField)->getLocation(),
+ << FD << FD->getType() << FDStorageSize.getQuantity()
+ << PreviousFieldStorageSize.getQuantity();
+ Diag(PreviousField->getLocation(),
diag::note_ms_bitfield_mismatched_storage_size_previous)
- << *PreviousField << (*PreviousField)->getType();
+ << PreviousField << PreviousField->getType();
}
}
// Keep track of the number of named members.
diff --git a/clang/test/SemaCXX/ms_struct-bitfield-padding.cpp
b/clang/test/SemaCXX/ms_struct-bitfield-padding.cpp
index 001086de5bbd10..11a786d47dd0ac 100644
--- a/clang/test/SemaCXX/ms_struct-bitfield-padding.cpp
+++ b/clang/test/SemaCXX/ms_struct-bitfield-padding.cpp
@@ -55,7 +55,7 @@ static_assert(sizeof(F) == 4);
struct G {
EnumU32_1 a : 15;
EnumU64 b : 15;
- // expected-warning@-1 {{bit-field 'b' of type 'EnumU64' has a different
storage size (8 vs 4 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-warning@-1 {{bit-field 'b' of type 'EnumU64' has a different
storage size than the preceding bit-field (8 vs 4 bytes) and will not be packed
under the MSVC ABI}}
// expected-note@-3 {{preceding bit-field 'a' declared here with type
'EnumU32_1'}}
};
@@ -76,7 +76,7 @@ struct I {
EnumU8 a : 3;
EnumI8 b : 5;
EnumU32_1 c : 10;
- // expected-warning@-1 {{bit-field 'c' of type 'EnumU32_1' has a different
storage size (4 vs 1 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-warning@-1 {{bit-field 'c' of type 'EnumU32_1' has a different
storage size than the preceding bit-field (4 vs 1 bytes) and will not be packed
under the MSVC ABI}}
// expected-note@-3 {{preceding bit-field 'b' declared here with type
'EnumI8'}}
};
#ifdef MS_BITFIELDS
@@ -116,10 +116,10 @@ static_assert(sizeof(M) == 4);
struct N {
EnumU32_1 a : 10;
EnumU64 b : 10;
- // expected-warning@-1 {{bit-field 'b' of type 'EnumU64' has a different
storage size (8 vs 4 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-warning@-1 {{bit-field 'b' of type 'EnumU64' has a different
storage size than the preceding bit-field (8 vs 4 bytes) and will not be packed
under the MSVC ABI}}
// expected-note@-3 {{preceding bit-field 'a' declared here with type
'EnumU32_1'}}
EnumU32_1 c : 10;
- // expected-warning@-1 {{bit-field 'c' of type 'EnumU32_1' has a different
storage size (4 vs 8 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-warning@-1 {{bit-field 'c' of type 'EnumU32_1' has a different
storage size than the preceding bit-field (4 vs 8 bytes) and will not be packed
under the MSVC ABI}}
// expected-note@-5 {{preceding bit-field 'b' declared here with type
'EnumU64'}}
};
@@ -132,7 +132,7 @@ static_assert(sizeof(N) == 8);
struct O {
EnumU16 a : 10;
EnumU32_1 b : 10;
- // expected-warning@-1 {{bit-field 'b' of type 'EnumU32_1' has a different
storage size (4 vs 2 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-warning@-1 {{bit-field 'b' of type 'EnumU32_1' has a different
storage size than the preceding bit-field (4 vs 2 bytes) and will not be packed
under the MSVC ABI}}
// expected-note@-3 {{preceding bit-field 'a' declared here with type
'EnumU16'}}
};
#ifdef MS_BITFIELDS
@@ -144,7 +144,7 @@ static_assert(sizeof(O) == 4);
struct P {
EnumU32_1 a : 10;
EnumU16 b : 10;
- // expected-warning@-1 {{bit-field 'b' of type 'EnumU16' has a different
storage size (2 vs 4 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-warning@-1 {{bit-field 'b' of type 'EnumU16' has a different
storage size than the preceding bit-field (2 vs 4 bytes) and will not be packed
under the MSVC ABI}}
// expected-note@-3 {{preceding bit-field 'a' declared here with type
'EnumU32_1'}}
};
#ifdef MS_BITFIELDS
@@ -156,7 +156,7 @@ static_assert(sizeof(P) == 4);
struct Q {
EnumU8 a : 6;
EnumU16 b : 6;
- // expected-warning@-1 {{bit-field 'b' of type 'EnumU16' has a different
storage size (2 vs 1 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-warning@-1 {{bit-field 'b' of type 'EnumU16' has a different
storage size than the preceding bit-field (2 vs 1 bytes) and will not be packed
under the MSVC ABI}}
// expected-note@-3 {{preceding bit-field 'a' declared here with type
'EnumU8'}}
};
#ifdef MS_BITFIELDS
@@ -169,7 +169,7 @@ struct R {
EnumU16 a : 9;
EnumU16 b : 9;
EnumU8 c : 6;
- // expected-warning@-1 {{bit-field 'c' of type 'EnumU8' has a different
storage size (1 vs 2 bytes) than the preceding bit-field and may not be packed
under MSVC ABI}}
+ // expected-warning@-1 {{bit-field 'c' of type 'EnumU8' has a different
storage size than the preceding bit-field (1 vs 2 bytes) and will not be packed
under the MSVC ABI}}
// expected-note@-3 {{preceding bit-field 'b' declared here with type
'EnumU16'}}
};
>From a18c032c7b7b57be64d0f60aa7768b078adae992 Mon Sep 17 00:00:00 2001
From: Oliver Hunt <oli...@apple.com>
Date: Sun, 1 Dec 2024 23:23:47 -0800
Subject: [PATCH 3/4] Documentation and renaming
---
clang/include/clang/Basic/DiagnosticGroups.td | 45 ++++++++++++++++++-
.../SemaCXX/ms_struct-bitfield-padding.cpp | 2 +-
2 files changed, 45 insertions(+), 2 deletions(-)
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td
b/clang/include/clang/Basic/DiagnosticGroups.td
index 69fae8c650ec9c..7e679169302fbd 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -631,7 +631,50 @@ def Packed : DiagGroup<"packed", [PackedNonPod]>;
def PaddedBitField : DiagGroup<"padded-bitfield">;
def Padded : DiagGroup<"padded", [PaddedBitField]>;
def UnalignedAccess : DiagGroup<"unaligned-access">;
-def MSBitfieldCompatibility : DiagGroup<"ms-bitfield-packing-compatibility">;
+def MSBitfieldCompatibility : DiagGroup<"ms-bitfield-compatibility"> {
+ code Documentation = [{
+ Under the MSVC ABI adjacemt bit-fields are not packed if the underlying
type
+ has a different storage size. This warning indicates that a pair of
adjacent
+ bit-fields may not pack in the same way due to this behavioural difference.
+
+ This can occur when mixing different types explicitly:
+
+ .. code-block:: c++
+
+ struct S {
+ uint16_t field1 : 1;
+ uint32_t field2 : 1;
+ };
+
+ or more subtly through enums
+
+ .. code-block:: c++
+
+ enum Enum1 { /* ... */ };
+ enum class Enum2 : unsigned char { /* ... */ };
+ struct S {
+ Enum1 field1 : 1;
+ Enum2 field2 : 1;
+ };
+
+ In each of these cases under the MSVC ABI the second bit-field will not be
+ packed with the preceding bit-field, and instead will be aligned as if the
+ fields were each separately defined integer fields of their respective
storage
+ size. For binary compatibility this is obviously and observably
incompatible,
+ however where bit-fields are being used solely for memory use reduction
this
+ incomplete packing may silently increase the size of objects vs what is
+ expected.
+
+ This issue can be addressed by ensuring the storage type of each bit-field
is
+ the same, either by explicitly using the same integer type, or in the case
of
+ enum types declaring the enum types with the same storage size. For enum
types
+ where you cannot specify the underlying type, the options are to either
switch
+ to int sized storage for all specifiers or to resort to declaring the
+ bit-fields with explicit integer storage types and cast in and out of the
field.
+ If such a solution is required the `preferred_type` attribute can be used
to
+ convey the actual field type to debuggers and other tooling.
+ }];
+}
def PessimizingMove : DiagGroup<"pessimizing-move">;
def ReturnStdMove : DiagGroup<"return-std-move">;
diff --git a/clang/test/SemaCXX/ms_struct-bitfield-padding.cpp
b/clang/test/SemaCXX/ms_struct-bitfield-padding.cpp
index 11a786d47dd0ac..fd1eb30bfe3769 100644
--- a/clang/test/SemaCXX/ms_struct-bitfield-padding.cpp
+++ b/clang/test/SemaCXX/ms_struct-bitfield-padding.cpp
@@ -1,5 +1,5 @@
-// RUN: %clang_cc1 -fsyntax-only -Wms-bitfield-packing-compatibility -verify
-triple armv8 -std=c++23 %s
+// RUN: %clang_cc1 -fsyntax-only -Wms-bitfield-compatibility -verify -triple
armv8 -std=c++23 %s
// RUN: %clang_cc1 -fsyntax-only -DMS_BITFIELDS -mms-bitfields
-verify=msbitfields -triple armv8-apple-macos10.15 -std=c++23 %s
// msbitfields-no-diagnostics
>From 75a46fe44b70f565bbe7f1ac0ee1ddf1bb0c171e Mon Sep 17 00:00:00 2001
From: Oliver Hunt <oli...@apple.com>
Date: Sun, 1 Dec 2024 23:30:16 -0800
Subject: [PATCH 4/4] Add release note
---
clang/docs/ReleaseNotes.rst | 3 +++
1 file changed, 3 insertions(+)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index e44aefa90ab386..5605656c3df485 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -629,6 +629,9 @@ Improvements to Clang's diagnostics
- Clang now diagnoses dangling references for C++20's parenthesized aggregate
initialization (#101957).
+- A new off-by-default warning ``-Wms-bitfield-compatibility`` has been added
to alert to cases where bit-field
+ packing may differ under the MS struct ABI (#GH117428).
+
Improvements to Clang's time-trace
----------------------------------
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
