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[lldb][DWARFASTParserClang][NFCI] Extract DW_AT_data_member_location calculation logic #68231

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Oct 5, 2023
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[lldb][DWARFASTParserClang][NFCI] Extract DW_AT_data_member_location calculation logic #68231

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126 changes: 39 additions & 87 deletions lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -519,6 +519,33 @@ TypeSP DWARFASTParserClang::ParseTypeFromDWARF(const SymbolContext &sc,
return UpdateSymbolContextScopeForType(sc, die, type_sp);
}

static std::optional<uint32_t>
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@Michael137 Michael137 Oct 4, 2023 •
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The integer types are a bit inconsistent (but this didn't change with this patch).

  • ParseInheritance stores the value in an off_t. Then passes it to clang::CharUnits::fromQuantity which takes an int64_t
  • The Rust Variant support stores offsets as uint32_t, and so does MemberAttributes. But FormValue::Unsigned() returns a uint64_t.

ExtractDataMemberLocation(DWARFDIE const &die, DWARFFormValue const &form_value,
ModuleSP module_sp) {
// With DWARF 3 and later, if the value is an integer constant,
// this form value is the offset in bytes from the beginning of
// the containing entity.
if (!form_value.BlockData())
return form_value.Unsigned();

Value initialValue(0);
Value memberOffset(0);
const DWARFDataExtractor &debug_info_data = die.GetData();
uint32_t block_length = form_value.Unsigned();
uint32_t block_offset =
form_value.BlockData() - debug_info_data.GetDataStart();
if (!DWARFExpression::Evaluate(
nullptr, // ExecutionContext *
nullptr, // RegisterContext *
module_sp, DataExtractor(debug_info_data, block_offset, block_length),
die.GetCU(), eRegisterKindDWARF, &initialValue, nullptr, memberOffset,
nullptr)) {
return {};
}

return memberOffset.ResolveValue(nullptr).UInt();
}

lldb::TypeSP
DWARFASTParserClang::ParseTypeModifier(const SymbolContext &sc,
const DWARFDIE &die,
Expand Down Expand Up @@ -1406,26 +1433,9 @@ void DWARFASTParserClang::ParseInheritance(
encoding_form = form_value;
break;
case DW_AT_data_member_location:
if (form_value.BlockData()) {
Value initialValue(0);
Value memberOffset(0);
const DWARFDataExtractor &debug_info_data = die.GetData();
uint32_t block_length = form_value.Unsigned();
uint32_t block_offset =
form_value.BlockData() - debug_info_data.GetDataStart();
if (DWARFExpression::Evaluate(
nullptr, nullptr, module_sp,
DataExtractor(debug_info_data, block_offset, block_length),
die.GetCU(), eRegisterKindDWARF, &initialValue, nullptr,
memberOffset, nullptr)) {
member_byte_offset = memberOffset.ResolveValue(nullptr).UInt();
}
} else {
// With DWARF 3 and later, if the value is an integer constant,
// this form value is the offset in bytes from the beginning of
// the containing entity.
member_byte_offset = form_value.Unsigned();
}
if (auto maybe_offset =
ExtractDataMemberLocation(die, form_value, module_sp))
member_byte_offset = *maybe_offset;
break;

case DW_AT_accessibility:
Expand Down Expand Up @@ -2557,29 +2567,9 @@ VariantMember::VariantMember(DWARFDIE &die, lldb::ModuleSP module_sp) {
break;

case DW_AT_data_member_location:
if (form_value.BlockData()) {
Value initialValue(0);
Value memberOffset(0);
const DWARFDataExtractor &debug_info_data = die.GetData();
uint32_t block_length = form_value.Unsigned();
uint32_t block_offset =
form_value.BlockData() - debug_info_data.GetDataStart();
if (DWARFExpression::Evaluate(
nullptr, // ExecutionContext *
nullptr, // RegisterContext *
module_sp,
DataExtractor(debug_info_data, block_offset,
block_length),
die.GetCU(), eRegisterKindDWARF, &initialValue, nullptr,
memberOffset, nullptr)) {
byte_offset = memberOffset.ResolveValue(nullptr).UInt();
}
} else {
// With DWARF 3 and later, if the value is an integer constant,
// this form value is the offset in bytes from the beginning of
// the containing entity.
byte_offset = form_value.Unsigned();
}
if (auto maybe_offset =
ExtractDataMemberLocation(die, form_value, module_sp))
byte_offset = *maybe_offset;
break;

default:
Expand Down Expand Up @@ -2608,28 +2598,9 @@ DiscriminantValue::DiscriminantValue(const DWARFDIE &die, ModuleSP module_sp) {
type_ref = form_value;
break;
case DW_AT_data_member_location:
if (form_value.BlockData()) {
Value initialValue(0);
Value memberOffset(0);
const DWARFDataExtractor &debug_info_data = die.GetData();
uint32_t block_length = form_value.Unsigned();
uint32_t block_offset =
form_value.BlockData() - debug_info_data.GetDataStart();
if (DWARFExpression::Evaluate(
nullptr, // ExecutionContext *
nullptr, // RegisterContext *
module_sp,
DataExtractor(debug_info_data, block_offset, block_length),
die.GetCU(), eRegisterKindDWARF, &initialValue, nullptr,
memberOffset, nullptr)) {
byte_offset = memberOffset.ResolveValue(nullptr).UInt();
}
} else {
// With DWARF 3 and later, if the value is an integer constant,
// this form value is the offset in bytes from the beginning of
// the containing entity.
byte_offset = form_value.Unsigned();
}
if (auto maybe_offset =
ExtractDataMemberLocation(die, form_value, module_sp))
byte_offset = *maybe_offset;
break;
default:
break;
Expand Down Expand Up @@ -2686,28 +2657,9 @@ MemberAttributes::MemberAttributes(const DWARFDIE &die,
data_bit_offset = form_value.Unsigned();
break;
case DW_AT_data_member_location:
if (form_value.BlockData()) {
Value initialValue(0);
Value memberOffset(0);
const DWARFDataExtractor &debug_info_data = die.GetData();
uint32_t block_length = form_value.Unsigned();
uint32_t block_offset =
form_value.BlockData() - debug_info_data.GetDataStart();
if (DWARFExpression::Evaluate(
nullptr, // ExecutionContext *
nullptr, // RegisterContext *
module_sp,
DataExtractor(debug_info_data, block_offset, block_length),
die.GetCU(), eRegisterKindDWARF, &initialValue, nullptr,
memberOffset, nullptr)) {
member_byte_offset = memberOffset.ResolveValue(nullptr).UInt();
}
} else {
// With DWARF 3 and later, if the value is an integer constant,
// this form value is the offset in bytes from the beginning of
// the containing entity.
member_byte_offset = form_value.Unsigned();
}
if (auto maybe_offset =
ExtractDataMemberLocation(die, form_value, module_sp))
member_byte_offset = *maybe_offset;
break;

case DW_AT_accessibility:
Expand Down