[Lldb-commits] [lldb] [lldb][DWARFASTParserClang] Don't overwrite DW_AT_object_pointer of definition with that of a declaration (PR #123089)
Michael Buch via lldb-commits
lldb-commits at lists.llvm.org
Wed Jan 15 09:04:38 PST 2025
https://github.com/Michael137 created https://github.com/llvm/llvm-project/pull/123089
In https://github.com/llvm/llvm-project/pull/122742 we will start attaching DW_AT_object_pointer to method declarations (in addition to definitions).
Currently when LLDB parses a `DW_TAG_subprogram` definition, it will parse all the attributes of the declaration as well. If we have `DW_AT_object_pointer` on both, then we would overwrite the more specific attribute that we got from the defintion with the one from the specification. This is problematic because LLDB relies on getting the `DW_AT_name` from the `DW_AT_object_pointer`, which doesn't exist on the specification.
>From 3b83db4a912d01b6f416e8873f9fbe8fb598ff0c Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12 at gmail.com>
Date: Wed, 15 Jan 2025 16:58:53 +0000
Subject: [PATCH] [lldb][DWARFASTParserClang] Don't overwrite
DW_AT_object_pointer of definition with that of a declaration
In https://github.com/llvm/llvm-project/pull/122742 we will start attaching DW_AT_object_pointer to method declarations (in addition to definitions).
Currently when LLDB parses a `DW_TAG_subprogram` definition, it will
parse all the attributes of the declaration as well. If we have
`DW_AT_object_pointer` on both, then we would overwrite the more
specific attribute that we got from the defintion with the one from the
specification. This is problematic because LLDB relies on getting the
`DW_AT_name` from the `DW_AT_object_pointer`, which doesn't exist on the
specification.
---
.../SymbolFile/DWARF/DWARFASTParserClang.cpp | 7 +-
.../DWARF/DWARFASTParserClangTests.cpp | 161 ++++++++++++++++++
2 files changed, 167 insertions(+), 1 deletion(-)
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
index e2f76e88dd6f0f..fb3af44abfa8d4 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -377,7 +377,12 @@ ParsedDWARFTypeAttributes::ParsedDWARFTypeAttributes(const DWARFDIE &die) {
break;
case DW_AT_object_pointer:
- object_pointer = form_value.Reference();
+ // GetAttributes follows DW_AT_specification.
+ // DW_TAG_subprogram definitions and declarations may both
+ // have a DW_AT_object_pointer. Don't overwrite the one
+ // we parsed for the definition with the one from the declaration.
+ if (!object_pointer.IsValid())
+ object_pointer = form_value.Reference();
break;
case DW_AT_signature:
diff --git a/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp b/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp
index f22d76b3973e5f..b31f56aa372d58 100644
--- a/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp
+++ b/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp
@@ -741,3 +741,164 @@ TEST_F(DWARFASTParserClangTests, TestUniqueDWARFASTTypeMap_CppInsertMapFind) {
ASSERT_EQ(type_sp, reparsed_type_sp);
}
+
+TEST_F(DWARFASTParserClangTests, TestParseDWARFAttributes_ObjectPointer) {
+ // This tests the behaviour of ParsedDWARFTypeAttributes
+ // for DW_TAG_subprogram definitions which have a DW_AT_object_pointer
+ // *and* a DW_AT_specification that also has a DW_AT_object_pointer.
+ // We don't want the declaration DW_AT_object_pointer to overwrite the
+ // one from the more specific definition's.
+
+ const char *yamldata = R"(
+--- !ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_EXEC
+ Machine: EM_AARCH64
+DWARF:
+ debug_str:
+ - Context
+ - func
+ - this
+ debug_abbrev:
+ - ID: 0
+ Table:
+ - Code: 0x1
+ Tag: DW_TAG_compile_unit
+ Children: DW_CHILDREN_yes
+ Attributes:
+ - Attribute: DW_AT_language
+ Form: DW_FORM_data2
+ - Code: 0x2
+ Tag: DW_TAG_structure_type
+ Children: DW_CHILDREN_yes
+ Attributes:
+ - Attribute: DW_AT_name
+ Form: DW_FORM_strp
+ - Code: 0x3
+ Tag: DW_TAG_subprogram
+ Children: DW_CHILDREN_yes
+ Attributes:
+ - Attribute: DW_AT_name
+ Form: DW_FORM_strp
+ - Attribute: DW_AT_declaration
+ Form: DW_FORM_flag_present
+ - Attribute: DW_AT_object_pointer
+ Form: DW_FORM_ref4
+ - Attribute: DW_AT_artificial
+ Form: DW_FORM_flag_present
+ - Attribute: DW_AT_external
+ Form: DW_FORM_flag_present
+ - Code: 0x4
+ Tag: DW_TAG_formal_parameter
+ Children: DW_CHILDREN_no
+ Attributes:
+ - Attribute: DW_AT_artificial
+ Form: DW_FORM_flag_present
+ - Code: 0x5
+ Tag: DW_TAG_subprogram
+ Children: DW_CHILDREN_yes
+ Attributes:
+ - Attribute: DW_AT_object_pointer
+ Form: DW_FORM_ref4
+ - Attribute: DW_AT_specification
+ Form: DW_FORM_ref4
+ - Code: 0x6
+ Tag: DW_TAG_formal_parameter
+ Children: DW_CHILDREN_no
+ Attributes:
+ - Attribute: DW_AT_name
+ Form: DW_FORM_strp
+ - Attribute: DW_AT_artificial
+ Form: DW_FORM_flag_present
+ debug_info:
+ - Version: 5
+ UnitType: DW_UT_compile
+ AddrSize: 8
+ Entries:
+
+# DW_TAG_compile_unit
+# DW_AT_language [DW_FORM_data2] (DW_LANG_C_plus_plus)
+
+ - AbbrCode: 0x1
+ Values:
+ - Value: 0x04
+
+# DW_TAG_structure_type
+# DW_AT_name [DW_FORM_strp] ("Context")
+
+ - AbbrCode: 0x2
+ Values:
+ - Value: 0x0
+
+# DW_TAG_subprogram
+# DW_AT_name [DW_FORM_strp] ("func")
+# DW_AT_object_pointer [DW_FORM_ref4]
+ - AbbrCode: 0x3
+ Values:
+ - Value: 0x8
+ - Value: 0x1
+ - Value: 0x1d
+ - Value: 0x1
+ - Value: 0x1
+
+# DW_TAG_formal_parameter
+# DW_AT_artificial
+ - AbbrCode: 0x4
+ Values:
+ - Value: 0x1
+
+ - AbbrCode: 0x0
+ - AbbrCode: 0x0
+
+# DW_TAG_subprogram
+# DW_AT_object_pointer [DW_FORM_ref4] ("this")
+# DW_AT_specification [DW_FORM_ref4] ("func")
+ - AbbrCode: 0x5
+ Values:
+ - Value: 0x29
+ - Value: 0x14
+
+# DW_TAG_formal_parameter
+# DW_AT_name [DW_FORM_strp] ("this")
+# DW_AT_artificial
+ - AbbrCode: 0x6
+ Values:
+ - Value: 0xd
+ - Value: 0x1
+
+ - AbbrCode: 0x0
+ - AbbrCode: 0x0
+...
+)";
+ YAMLModuleTester t(yamldata);
+
+ DWARFUnit *unit = t.GetDwarfUnit();
+ ASSERT_NE(unit, nullptr);
+ const DWARFDebugInfoEntry *cu_entry = unit->DIE().GetDIE();
+ ASSERT_EQ(cu_entry->Tag(), DW_TAG_compile_unit);
+ ASSERT_EQ(unit->GetDWARFLanguageType(), DW_LANG_C_plus_plus);
+ DWARFDIE cu_die(unit, cu_entry);
+
+ auto holder = std::make_unique<clang_utils::TypeSystemClangHolder>("ast");
+ auto &ast_ctx = *holder->GetAST();
+ DWARFASTParserClangStub ast_parser(ast_ctx);
+
+ auto context_die = cu_die.GetFirstChild();
+ ASSERT_TRUE(context_die.IsValid());
+ ASSERT_EQ(context_die.Tag(), DW_TAG_structure_type);
+
+ auto subprogram_definition = context_die.GetSibling();
+ ASSERT_TRUE(subprogram_definition.IsValid());
+ ASSERT_EQ(subprogram_definition.Tag(), DW_TAG_subprogram);
+ ASSERT_FALSE(subprogram_definition.GetAttributeValueAsOptionalUnsigned(
+ DW_AT_external));
+
+ auto param_die = subprogram_definition.GetFirstChild();
+ ASSERT_TRUE(param_die.IsValid());
+
+ ParsedDWARFTypeAttributes attrs(subprogram_definition);
+ EXPECT_TRUE(attrs.object_pointer.IsValid());
+ EXPECT_EQ(attrs.object_pointer, param_die);
+}
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