[clang] 76fa953 - [clang] add support for -Wpadded on Windows (#130182)
via cfe-commits
cfe-commits at lists.llvm.org
Wed Apr 2 14:47:01 PDT 2025
Author: Theo de Magalhaes
Date: 2025-04-02T14:46:58-07:00
New Revision: 76fa9530c9ac7f81a49b840556f51f4838efbfe1
URL: https://github.com/llvm/llvm-project/commit/76fa9530c9ac7f81a49b840556f51f4838efbfe1
DIFF: https://github.com/llvm/llvm-project/commit/76fa9530c9ac7f81a49b840556f51f4838efbfe1.diff
LOG: [clang] add support for -Wpadded on Windows (#130182)
Implements the -Wpadded warning for --target=x86_64-windows-msvc etc.
Fixes #61702 .
Added:
clang/test/SemaCXX/windows-Wpadded-bitfield.cpp
clang/test/SemaCXX/windows-Wpadded.cpp
Modified:
clang/docs/ReleaseNotes.rst
clang/lib/AST/RecordLayoutBuilder.cpp
Removed:
################################################################################
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 3f7f723bc96ce..7fb6b0baae16b 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -190,6 +190,8 @@ Modified Compiler Flags
- The compiler flag `-fbracket-depth` default value is increased from 256 to 2048. (#GH94728)
+- `-Wpadded` option implemented for the `x86_64-windows-msvc` target. Fixes #61702
+
Removed Compiler Flags
-------------------------
diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 3e756ab9b9bfe..41e7198cb7581 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -2274,9 +2274,9 @@ static unsigned getPaddingDiagFromTagKind(TagTypeKind Tag) {
}
}
-void ItaniumRecordLayoutBuilder::CheckFieldPadding(
- uint64_t Offset, uint64_t UnpaddedOffset, uint64_t UnpackedOffset,
- unsigned UnpackedAlign, bool isPacked, const FieldDecl *D) {
+static void CheckFieldPadding(const ASTContext &Context, bool IsUnion,
+ uint64_t Offset, uint64_t UnpaddedOffset,
+ const FieldDecl *D) {
// We let objc ivars without warning, objc interfaces generally are not used
// for padding tricks.
if (isa<ObjCIvarDecl>(D))
@@ -2300,7 +2300,8 @@ void ItaniumRecordLayoutBuilder::CheckFieldPadding(
if (D->getIdentifier()) {
auto Diagnostic = D->isBitField() ? diag::warn_padded_struct_bitfield
: diag::warn_padded_struct_field;
- Diag(D->getLocation(), Diagnostic)
+ Context.getDiagnostics().Report(D->getLocation(),
+ Diagnostic)
<< getPaddingDiagFromTagKind(D->getParent()->getTagKind())
<< Context.getTypeDeclType(D->getParent()) << PadSize
<< (InBits ? 1 : 0) // (byte|bit)
@@ -2308,15 +2309,22 @@ void ItaniumRecordLayoutBuilder::CheckFieldPadding(
} else {
auto Diagnostic = D->isBitField() ? diag::warn_padded_struct_anon_bitfield
: diag::warn_padded_struct_anon_field;
- Diag(D->getLocation(), Diagnostic)
+ Context.getDiagnostics().Report(D->getLocation(),
+ Diagnostic)
<< getPaddingDiagFromTagKind(D->getParent()->getTagKind())
<< Context.getTypeDeclType(D->getParent()) << PadSize
<< (InBits ? 1 : 0); // (byte|bit)
}
- }
- if (isPacked && Offset != UnpackedOffset) {
- HasPackedField = true;
- }
+ }
+}
+
+void ItaniumRecordLayoutBuilder::CheckFieldPadding(
+ uint64_t Offset, uint64_t UnpaddedOffset, uint64_t UnpackedOffset,
+ unsigned UnpackedAlign, bool isPacked, const FieldDecl *D) {
+ ::CheckFieldPadding(Context, IsUnion, Offset, UnpaddedOffset, D);
+ if (isPacked && Offset != UnpackedOffset) {
+ HasPackedField = true;
+ }
}
static const CXXMethodDecl *computeKeyFunction(ASTContext &Context,
@@ -2642,8 +2650,6 @@ struct MicrosoftRecordLayoutBuilder {
/// virtual base classes and their offsets in the record.
ASTRecordLayout::VBaseOffsetsMapTy VBases;
/// The number of remaining bits in our last bitfield allocation.
- /// This value isn't meaningful unless LastFieldIsNonZeroWidthBitfield is
- /// true.
unsigned RemainingBitsInField;
bool IsUnion : 1;
/// True if the last field laid out was a bitfield and was not 0
@@ -3004,6 +3010,15 @@ void MicrosoftRecordLayoutBuilder::layoutField(const FieldDecl *FD) {
} else {
FieldOffset = Size.alignTo(Info.Alignment);
}
+
+ uint64_t UnpaddedFielddOffsetInBits =
+ Context.toBits(DataSize) - RemainingBitsInField;
+
+ ::CheckFieldPadding(Context, IsUnion, Context.toBits(FieldOffset),
+ UnpaddedFielddOffsetInBits, FD);
+
+ RemainingBitsInField = 0;
+
placeFieldAtOffset(FieldOffset);
if (!IsOverlappingEmptyField)
@@ -3049,10 +3064,14 @@ void MicrosoftRecordLayoutBuilder::layoutBitField(const FieldDecl *FD) {
} else {
// Allocate a new block of memory and place the bitfield in it.
CharUnits FieldOffset = Size.alignTo(Info.Alignment);
+ uint64_t UnpaddedFieldOffsetInBits =
+ Context.toBits(DataSize) - RemainingBitsInField;
placeFieldAtOffset(FieldOffset);
Size = FieldOffset + Info.Size;
Alignment = std::max(Alignment, Info.Alignment);
RemainingBitsInField = Context.toBits(Info.Size) - Width;
+ ::CheckFieldPadding(Context, IsUnion, Context.toBits(FieldOffset),
+ UnpaddedFieldOffsetInBits, FD);
}
DataSize = Size;
}
@@ -3076,9 +3095,14 @@ MicrosoftRecordLayoutBuilder::layoutZeroWidthBitField(const FieldDecl *FD) {
} else {
// Round up the current record size to the field's alignment boundary.
CharUnits FieldOffset = Size.alignTo(Info.Alignment);
+ uint64_t UnpaddedFieldOffsetInBits =
+ Context.toBits(DataSize) - RemainingBitsInField;
placeFieldAtOffset(FieldOffset);
+ RemainingBitsInField = 0;
Size = FieldOffset;
Alignment = std::max(Alignment, Info.Alignment);
+ ::CheckFieldPadding(Context, IsUnion, Context.toBits(FieldOffset),
+ UnpaddedFieldOffsetInBits, FD);
}
DataSize = Size;
}
@@ -3203,6 +3227,9 @@ void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {
}
void MicrosoftRecordLayoutBuilder::finalizeLayout(const RecordDecl *RD) {
+ uint64_t UnpaddedSizeInBits = Context.toBits(DataSize);
+ UnpaddedSizeInBits -= RemainingBitsInField;
+
// Respect required alignment. Note that in 32-bit mode Required alignment
// may be 0 and cause size not to be updated.
DataSize = Size;
@@ -3231,6 +3258,22 @@ void MicrosoftRecordLayoutBuilder::finalizeLayout(const RecordDecl *RD) {
Size = Context.toCharUnitsFromBits(External.Size);
if (External.Align)
Alignment = Context.toCharUnitsFromBits(External.Align);
+ return;
+ }
+ unsigned CharBitNum = Context.getTargetInfo().getCharWidth();
+ uint64_t SizeInBits = Context.toBits(Size);
+ if (SizeInBits > UnpaddedSizeInBits) {
+ unsigned int PadSize = SizeInBits - UnpaddedSizeInBits;
+ bool InBits = true;
+ if (PadSize % CharBitNum == 0) {
+ PadSize = PadSize / CharBitNum;
+ InBits = false;
+ }
+
+ Context.getDiagnostics().Report(RD->getLocation(),
+ diag::warn_padded_struct_size)
+ << Context.getTypeDeclType(RD) << PadSize
+ << (InBits ? 1 : 0); // (byte|bit)
}
}
diff --git a/clang/test/SemaCXX/windows-Wpadded-bitfield.cpp b/clang/test/SemaCXX/windows-Wpadded-bitfield.cpp
new file mode 100644
index 0000000000000..ee5a57124eca5
--- /dev/null
+++ b/clang/test/SemaCXX/windows-Wpadded-bitfield.cpp
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -fsyntax-only -verify -Wpadded %s
+
+struct __attribute__((ms_struct)) BitfieldStruct { // expected-warning {{padding size of 'BitfieldStruct' with 3 bytes to alignment boundary}}
+ char c : 1;
+ int : 0; // expected-warning {{padding struct 'BitfieldStruct' with 31 bits to align anonymous bit-field}}
+ char i;
+};
+
+struct __attribute__((ms_struct)) SevenBitfieldStruct { // expected-warning {{padding size of 'SevenBitfieldStruct' with 3 bytes to alignment boundary}}
+ char c : 7;
+ int : 0; // expected-warning {{padding struct 'SevenBitfieldStruct' with 25 bits to align anonymous bit-field}}
+ char i;
+};
+
+struct __attribute__((ms_struct)) SameUnitSizeBitfield {
+ char c : 7;
+ char : 1; // Same unit size attributes fall in the same unit + they fill the unit -> no padding
+ char i;
+};
+
+struct __attribute__((ms_struct)) DifferentUnitSizeBitfield { // expected-warning {{padding size of 'DifferentUnitSizeBitfield' with 3 bytes to alignment boundary}}
+ char c : 7;
+ int : 1; // expected-warning {{padding struct 'DifferentUnitSizeBitfield' with 25 bits to align anonymous bit-field}}
+ char i; // expected-warning {{padding struct 'DifferentUnitSizeBitfield' with 31 bits to align 'i'}}
+};
+
+int main() {
+ BitfieldStruct b;
+ SevenBitfieldStruct s;
+ SameUnitSizeBitfield su;
+ DifferentUnitSizeBitfield du;
+}
diff --git a/clang/test/SemaCXX/windows-Wpadded.cpp b/clang/test/SemaCXX/windows-Wpadded.cpp
new file mode 100644
index 0000000000000..da3f2bf08c6b8
--- /dev/null
+++ b/clang/test/SemaCXX/windows-Wpadded.cpp
@@ -0,0 +1,40 @@
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -fsyntax-only -verify -Wpadded %s
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -fsyntax-only -verify -Wpadded %s
+
+struct __attribute__((ms_struct)) Foo { // expected-warning {{padding size of 'Foo' with 3 bytes to alignment boundary}}
+ int b : 1;
+ char a; // expected-warning {{padding struct 'Foo' with 31 bits to align 'a'}}
+};
+
+struct __attribute__((ms_struct)) AlignedStruct { // expected-warning {{padding size of 'AlignedStruct' with 4 bytes to alignment boundary}}
+ char c;
+ alignas(8) int i; // expected-warning {{padding struct 'AlignedStruct' with 7 bytes to align 'i'}}
+};
+
+
+struct Base {
+ int b;
+};
+
+struct Derived : public Base { // expected-warning {{padding size of 'Derived' with 3 bytes to alignment boundary}}
+ char c;
+};
+
+union __attribute__((ms_struct)) Union {
+ char c;
+ long long u;
+};
+
+struct __attribute__((ms_struct)) StructWithUnion { // expected-warning {{padding size of 'StructWithUnion' with 6 bytes to alignment boundary}}
+ char c;
+ int : 0;
+ Union t; // expected-warning {{padding struct 'StructWithUnion' with 7 bytes to align 't'}}
+ short i;
+};
+
+int main() {
+ Foo f;
+ AlignedStruct a;
+ Derived d;
+ StructWithUnion swu;
+}
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