[clang] [lldb] [clang][lldb] Don't assert structure layout correctness for layouts provided by LLDB (PR #93809)
Michael Buch via cfe-commits
cfe-commits at lists.llvm.org
Thu May 30 04:56:30 PDT 2024
https://github.com/Michael137 updated https://github.com/llvm/llvm-project/pull/93809
>From 91276f5b2dc05032a285b465c0c8a69541bb25c4 Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12 at gmail.com>
Date: Thu, 2 May 2024 09:05:01 +0100
Subject: [PATCH 1/2] [clang][lldb] Don't assert structure layout correctness
for layouts provided by LLDB
This is the outcome of the discussions we had in
https://discourse.llvm.org/t/rfc-lldb-handling-no-unique-address-in-lldb/77483
To summarize, LLDB creates AST nodes by parsing debug-info and hands
those off to Clang for codegen. There are certain Clang attributes
that affect structure layout which are not encoded in DWARF, one of
which is `[[no_unique_address]]`. But the affects of such attributes
*is* encoded in DWARF in terms of member offsets and sizes. So some
of the correctness checks that the `RecordLayoutBuilder` performs
aren't really necessary for layouts provided by LLDB since we know that
the offsets we get from DWARF are correct (modulo corrupt DWARF).
Hence this patch guards those asserts behind the `DebuggerSupport` flag.
---
clang/lib/CodeGen/CGRecordLayoutBuilder.cpp | 18 ++++---
.../API/lang/cpp/no_unique_address/Makefile | 3 ++
.../no_unique_address/TestNoUniqueAddress.py | 50 +++++++++++++++++++
.../API/lang/cpp/no_unique_address/main.cpp | 35 +++++++++++++
4 files changed, 100 insertions(+), 6 deletions(-)
create mode 100644 lldb/test/API/lang/cpp/no_unique_address/Makefile
create mode 100644 lldb/test/API/lang/cpp/no_unique_address/TestNoUniqueAddress.py
create mode 100644 lldb/test/API/lang/cpp/no_unique_address/main.cpp
diff --git a/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp b/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
index 5169be204c14d..32fb032214e28 100644
--- a/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
+++ b/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
@@ -950,6 +950,9 @@ void CGRecordLowering::calculateZeroInit() {
// Verify accumulateBitfields computed the correct storage representations.
void CGRecordLowering::checkBitfieldClipping(bool IsNonVirtualBaseType) const {
#ifndef NDEBUG
+ if (Context.getLangOpts().DebuggerSupport)
+ return;
+
auto ScissorOffset = calculateTailClippingOffset(IsNonVirtualBaseType);
auto Tail = CharUnits::Zero();
for (const auto &M : Members) {
@@ -1008,7 +1011,8 @@ void CGRecordLowering::insertPadding() {
if (!Member->Data)
continue;
CharUnits Offset = Member->Offset;
- assert(Offset >= Size);
+ if (!Context.getLangOpts().DebuggerSupport)
+ assert(Offset >= Size);
// Insert padding if we need to.
if (Offset !=
Size.alignTo(Packed ? CharUnits::One() : getAlignment(Member->Data)))
@@ -1138,8 +1142,9 @@ CodeGenTypes::ComputeRecordLayout(const RecordDecl *D, llvm::StructType *Ty) {
const ASTRecordLayout &Layout = getContext().getASTRecordLayout(D);
uint64_t TypeSizeInBits = getContext().toBits(Layout.getSize());
- assert(TypeSizeInBits == getDataLayout().getTypeAllocSizeInBits(Ty) &&
- "Type size mismatch!");
+ if (!Context.getLangOpts().DebuggerSupport)
+ assert(TypeSizeInBits == getDataLayout().getTypeAllocSizeInBits(Ty) &&
+ "Type size mismatch!");
if (BaseTy) {
CharUnits NonVirtualSize = Layout.getNonVirtualSize();
@@ -1147,9 +1152,10 @@ CodeGenTypes::ComputeRecordLayout(const RecordDecl *D, llvm::StructType *Ty) {
uint64_t AlignedNonVirtualTypeSizeInBits =
getContext().toBits(NonVirtualSize);
- assert(AlignedNonVirtualTypeSizeInBits ==
- getDataLayout().getTypeAllocSizeInBits(BaseTy) &&
- "Type size mismatch!");
+ if (!Context.getLangOpts().DebuggerSupport)
+ assert(AlignedNonVirtualTypeSizeInBits ==
+ getDataLayout().getTypeAllocSizeInBits(BaseTy) &&
+ "Type size mismatch!");
}
// Verify that the LLVM and AST field offsets agree.
diff --git a/lldb/test/API/lang/cpp/no_unique_address/Makefile b/lldb/test/API/lang/cpp/no_unique_address/Makefile
new file mode 100644
index 0000000000000..99998b20bcb05
--- /dev/null
+++ b/lldb/test/API/lang/cpp/no_unique_address/Makefile
@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+
+include Makefile.rules
diff --git a/lldb/test/API/lang/cpp/no_unique_address/TestNoUniqueAddress.py b/lldb/test/API/lang/cpp/no_unique_address/TestNoUniqueAddress.py
new file mode 100644
index 0000000000000..373bcb9062cde
--- /dev/null
+++ b/lldb/test/API/lang/cpp/no_unique_address/TestNoUniqueAddress.py
@@ -0,0 +1,50 @@
+"""
+Test that LLDB correctly handles fields
+marked with [[no_unique_address]].
+"""
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+class NoUniqueAddressTestCase(TestBase):
+ def test(self):
+ self.build()
+ lldbutil.run_to_source_breakpoint(
+ self, "return 0", lldb.SBFileSpec("main.cpp", False)
+ )
+
+ # Qualified/unqualified lookup to templates in namespace
+ self.expect_expr("b1", result_type="basic::Foo", result_children=[ValueCheck(
+ name="a", type="Empty"
+ )])
+
+ self.expect_expr("b2", result_type="bases::Foo", result_children=[
+ ValueCheck(type="bases::B", children=[
+ ValueCheck(name="x", type="Empty")
+ ]),
+ ValueCheck(type="bases::A", children=[
+ ValueCheck(name="c", type="long", value="1"),
+ ValueCheck(name="d", type="long", value="2")
+ ]),
+ ValueCheck(type="bases::C", children=[
+ ValueCheck(name="x", type="Empty")
+ ]),
+ ])
+ self.expect_expr("b3", result_type="bases::Bar", result_children=[
+ ValueCheck(type="bases::B", children=[
+ ValueCheck(name="x", type="Empty")
+ ]),
+ ValueCheck(type="bases::C", children=[
+ ValueCheck(name="x", type="Empty")
+ ]),
+ ValueCheck(type="bases::A", children=[
+ ValueCheck(name="c", type="long", value="5"),
+ ValueCheck(name="d", type="long", value="6")
+ ]),
+ ])
+
+ self.expect("frame var b1")
+ self.expect("frame var b2")
+ self.expect("frame var b3")
diff --git a/lldb/test/API/lang/cpp/no_unique_address/main.cpp b/lldb/test/API/lang/cpp/no_unique_address/main.cpp
new file mode 100644
index 0000000000000..424fa90859cea
--- /dev/null
+++ b/lldb/test/API/lang/cpp/no_unique_address/main.cpp
@@ -0,0 +1,35 @@
+struct Empty {};
+
+namespace basic {
+struct Foo {
+ [[no_unique_address]] Empty a;
+};
+} // namespace basic
+
+namespace bases {
+struct A {
+ long c, d;
+};
+
+struct B {
+ [[no_unique_address]] Empty x;
+};
+
+struct C {
+ [[no_unique_address]] Empty x;
+};
+
+struct Foo : B, A, C {};
+struct Bar : B, C, A {};
+} // namespace bases
+
+int main() {
+ basic::Foo b1;
+ bases::Foo b2;
+ bases::Bar b3;
+ b2.c = 1;
+ b2.d = 2;
+ b3.c = 5;
+ b3.d = 6;
+ return 0;
+}
>From 882d231ac16ba635e9914900822b58f6ae9ced6d Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12 at gmail.com>
Date: Thu, 30 May 2024 12:56:19 +0100
Subject: [PATCH 2/2] fixup! clang-format
---
clang/lib/CodeGen/CGRecordLayoutBuilder.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp b/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
index 32fb032214e28..b7aab51660b5e 100644
--- a/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
+++ b/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
@@ -1154,7 +1154,7 @@ CodeGenTypes::ComputeRecordLayout(const RecordDecl *D, llvm::StructType *Ty) {
if (!Context.getLangOpts().DebuggerSupport)
assert(AlignedNonVirtualTypeSizeInBits ==
- getDataLayout().getTypeAllocSizeInBits(BaseTy) &&
+ getDataLayout().getTypeAllocSizeInBits(BaseTy) &&
"Type size mismatch!");
}
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