[Lldb-commits] [lldb] 9f5927e - [lldb/DWARF] Fix handling of variables with both location and const_value attributes
Pavel Labath via lldb-commits
lldb-commits at lists.llvm.org
Thu Aug 27 06:05:59 PDT 2020
Author: Pavel Labath
Date: 2020-08-27T15:05:47+02:00
New Revision: 9f5927e42bf4a7448dc9dd3a1550d1126c595dad
URL: https://github.com/llvm/llvm-project/commit/9f5927e42bf4a7448dc9dd3a1550d1126c595dad
DIFF: https://github.com/llvm/llvm-project/commit/9f5927e42bf4a7448dc9dd3a1550d1126c595dad.diff
LOG: [lldb/DWARF] Fix handling of variables with both location and const_value attributes
Class-level static constexpr variables can have both DW_AT_const_value
(in the "declaration") and a DW_AT_location (in the "definition")
attributes. Our code was trying to handle this, but it was brittle and
hard to follow (and broken) because it was processing the attributes in
the order in which they were found.
Refactor the code to make the intent clearer -- DW_AT_location trumps
DW_AT_const_value, and fix the bug which meant that we were not
displaying these variables properly (the culprit was the delayed parsing
of the const_value attribute due to a need to fetch the variable type.
Differential Revision: https://reviews.llvm.org/D86615
Added:
lldb/test/Shell/SymbolFile/DWARF/DW_AT_location-DW_AT_const_value.s
Modified:
lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.h
lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
Removed:
################################################################################
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.h
index b401352c693d..fe6a55520978 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.h
@@ -42,6 +42,7 @@ class DWARFFormValue {
DWARFFormValue(const DWARFUnit *unit) : m_unit(unit) {}
DWARFFormValue(const DWARFUnit *unit, dw_form_t form)
: m_unit(unit), m_form(form) {}
+ const DWARFUnit *GetUnit() const { return m_unit; }
void SetUnit(const DWARFUnit *unit) { m_unit = unit; }
dw_form_t Form() const { return m_form; }
dw_form_t& FormRef() { return m_form; }
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
index 500d7567536e..271821b24517 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -3111,18 +3111,15 @@ VariableSP SymbolFileDWARF::ParseVariableDIE(const SymbolContext &sc,
const char *name = nullptr;
const char *mangled = nullptr;
Declaration decl;
- uint32_t i;
DWARFFormValue type_die_form;
DWARFExpression location;
bool is_external = false;
bool is_artificial = false;
- bool location_is_const_value_data = false;
- bool has_explicit_location = false;
- DWARFFormValue const_value;
+ DWARFFormValue const_value_form, location_form;
Variable::RangeList scope_ranges;
// AccessType accessibility = eAccessNone;
- for (i = 0; i < num_attributes; ++i) {
+ for (size_t i = 0; i < num_attributes; ++i) {
dw_attr_t attr = attributes.AttributeAtIndex(i);
DWARFFormValue form_value;
@@ -3152,65 +3149,11 @@ VariableSP SymbolFileDWARF::ParseVariableDIE(const SymbolContext &sc,
is_external = form_value.Boolean();
break;
case DW_AT_const_value:
- // If we have already found a DW_AT_location attribute, ignore this
- // attribute.
- if (!has_explicit_location) {
- location_is_const_value_data = true;
- // The constant value will be either a block, a data value or a
- // string.
- auto debug_info_data = die.GetData();
- if (DWARFFormValue::IsBlockForm(form_value.Form())) {
- // Retrieve the value as a block expression.
- uint32_t block_offset =
- form_value.BlockData() - debug_info_data.GetDataStart();
- uint32_t block_length = form_value.Unsigned();
- location = DWARFExpression(
- module,
- DataExtractor(debug_info_data, block_offset, block_length),
- die.GetCU());
- } else if (DWARFFormValue::IsDataForm(form_value.Form())) {
- // Constant value size does not have to match the size of the
- // variable. We will fetch the size of the type after we create
- // it.
- const_value = form_value;
- } else if (const char *str = form_value.AsCString()) {
- uint32_t string_length = strlen(str) + 1;
- location = DWARFExpression(
- module,
- DataExtractor(str, string_length,
- die.GetCU()->GetByteOrder(),
- die.GetCU()->GetAddressByteSize()),
- die.GetCU());
- }
- }
+ const_value_form = form_value;
+ break;
+ case DW_AT_location:
+ location_form = form_value;
break;
- case DW_AT_location: {
- location_is_const_value_data = false;
- has_explicit_location = true;
- if (DWARFFormValue::IsBlockForm(form_value.Form())) {
- auto data = die.GetData();
-
- uint32_t block_offset =
- form_value.BlockData() - data.GetDataStart();
- uint32_t block_length = form_value.Unsigned();
- location = DWARFExpression(
- module, DataExtractor(data, block_offset, block_length),
- die.GetCU());
- } else {
- DataExtractor data = die.GetCU()->GetLocationData();
- dw_offset_t offset = form_value.Unsigned();
- if (form_value.Form() == DW_FORM_loclistx)
- offset = die.GetCU()->GetLoclistOffset(offset).getValueOr(-1);
- if (data.ValidOffset(offset)) {
- data = DataExtractor(data, offset, data.GetByteSize() - offset);
- location = DWARFExpression(module, data, die.GetCU());
- assert(func_low_pc != LLDB_INVALID_ADDRESS);
- location.SetLocationListAddresses(
- attributes.CompileUnitAtIndex(i)->GetBaseAddress(),
- func_low_pc);
- }
- }
- } break;
case DW_AT_specification:
spec_die = form_value.Reference();
break;
@@ -3236,6 +3179,66 @@ VariableSP SymbolFileDWARF::ParseVariableDIE(const SymbolContext &sc,
}
}
+ // Prefer DW_AT_location over DW_AT_const_value. Both can be emitted e.g.
+ // for static constexpr member variables -- DW_AT_const_value will be
+ // present in the class declaration and DW_AT_location in the DIE defining
+ // the member.
+ bool location_is_const_value_data = false;
+ bool has_explicit_location = false;
+ bool use_type_size_for_value = false;
+ if (location_form.IsValid()) {
+ has_explicit_location = true;
+ if (DWARFFormValue::IsBlockForm(location_form.Form())) {
+ const DWARFDataExtractor &data = die.GetData();
+
+ uint32_t block_offset =
+ location_form.BlockData() - data.GetDataStart();
+ uint32_t block_length = location_form.Unsigned();
+ location = DWARFExpression(
+ module, DataExtractor(data, block_offset, block_length),
+ die.GetCU());
+ } else {
+ DataExtractor data = die.GetCU()->GetLocationData();
+ dw_offset_t offset = location_form.Unsigned();
+ if (location_form.Form() == DW_FORM_loclistx)
+ offset = die.GetCU()->GetLoclistOffset(offset).getValueOr(-1);
+ if (data.ValidOffset(offset)) {
+ data = DataExtractor(data, offset, data.GetByteSize() - offset);
+ location = DWARFExpression(module, data, die.GetCU());
+ assert(func_low_pc != LLDB_INVALID_ADDRESS);
+ location.SetLocationListAddresses(
+ location_form.GetUnit()->GetBaseAddress(), func_low_pc);
+ }
+ }
+ } else if (const_value_form.IsValid()) {
+ location_is_const_value_data = true;
+ // The constant value will be either a block, a data value or a
+ // string.
+ const DWARFDataExtractor &debug_info_data = die.GetData();
+ if (DWARFFormValue::IsBlockForm(const_value_form.Form())) {
+ // Retrieve the value as a block expression.
+ uint32_t block_offset =
+ const_value_form.BlockData() - debug_info_data.GetDataStart();
+ uint32_t block_length = const_value_form.Unsigned();
+ location = DWARFExpression(
+ module,
+ DataExtractor(debug_info_data, block_offset, block_length),
+ die.GetCU());
+ } else if (DWARFFormValue::IsDataForm(const_value_form.Form())) {
+ // Constant value size does not have to match the size of the
+ // variable. We will fetch the size of the type after we create
+ // it.
+ use_type_size_for_value = true;
+ } else if (const char *str = const_value_form.AsCString()) {
+ uint32_t string_length = strlen(str) + 1;
+ location = DWARFExpression(
+ module,
+ DataExtractor(str, string_length, die.GetCU()->GetByteOrder(),
+ die.GetCU()->GetAddressByteSize()),
+ die.GetCU());
+ }
+ }
+
const DWARFDIE parent_context_die = GetDeclContextDIEContainingDIE(die);
const dw_tag_t parent_tag = die.GetParent().Tag();
bool is_static_member =
@@ -3415,12 +3418,12 @@ VariableSP SymbolFileDWARF::ParseVariableDIE(const SymbolContext &sc,
}
if (symbol_context_scope) {
- SymbolFileTypeSP type_sp(
- new SymbolFileType(*this, GetUID(type_die_form.Reference())));
+ auto type_sp = std::make_shared<SymbolFileType>(
+ *this, GetUID(type_die_form.Reference()));
- if (const_value.Form() && type_sp && type_sp->GetType())
+ if (use_type_size_for_value && type_sp->GetType())
location.UpdateValue(
- const_value.Unsigned(),
+ const_value_form.Unsigned(),
type_sp->GetType()->GetByteSize(nullptr).getValueOr(0),
die.GetCU()->GetAddressByteSize());
diff --git a/lldb/test/Shell/SymbolFile/DWARF/DW_AT_location-DW_AT_const_value.s b/lldb/test/Shell/SymbolFile/DWARF/DW_AT_location-DW_AT_const_value.s
new file mode 100644
index 000000000000..08ee77175f77
--- /dev/null
+++ b/lldb/test/Shell/SymbolFile/DWARF/DW_AT_location-DW_AT_const_value.s
@@ -0,0 +1,144 @@
+## Test that we don't get confused by variables with both location and
+## const_value attributes. Such values are produced in C++ for class-level
+## static constexpr variables.
+
+# REQUIRES: x86
+
+# RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux %s -o %t
+# RUN: %lldb %t -o "target variable A::x A::y" -o exit | FileCheck %s
+
+# CHECK-LABEL: target variable
+# CHECK: (const int) A::x = 142
+# CHECK: (const int) A::y = 242
+
+ .section .rodata,"a", at progbits
+ .p2align 2
+_ZN1A1xE:
+ .long 142
+_ZN1A1yE:
+ .long 242
+
+ .section .debug_abbrev,"", at progbits
+ .byte 1 # Abbreviation Code
+ .byte 17 # DW_TAG_compile_unit
+ .byte 1 # DW_CHILDREN_yes
+ .byte 37 # DW_AT_producer
+ .byte 8 # DW_FORM_string
+ .byte 3 # DW_AT_name
+ .byte 8 # DW_FORM_string
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 3 # Abbreviation Code
+ .byte 19 # DW_TAG_structure_type
+ .byte 1 # DW_CHILDREN_yes
+ .byte 3 # DW_AT_name
+ .byte 8 # DW_FORM_string
+ .byte 11 # DW_AT_byte_size
+ .byte 11 # DW_FORM_data1
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 4 # Abbreviation Code
+ .byte 13 # DW_TAG_member
+ .byte 0 # DW_CHILDREN_no
+ .byte 3 # DW_AT_name
+ .byte 8 # DW_FORM_string
+ .byte 73 # DW_AT_type
+ .byte 19 # DW_FORM_ref4
+ .byte 60 # DW_AT_declaration
+ .byte 25 # DW_FORM_flag_present
+ .byte 28 # DW_AT_const_value
+ .byte 13 # DW_FORM_sdata
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 5 # Abbreviation Code
+ .byte 38 # DW_TAG_const_type
+ .byte 0 # DW_CHILDREN_no
+ .byte 73 # DW_AT_type
+ .byte 19 # DW_FORM_ref4
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 6 # Abbreviation Code
+ .byte 36 # DW_TAG_base_type
+ .byte 0 # DW_CHILDREN_no
+ .byte 3 # DW_AT_name
+ .byte 8 # DW_FORM_string
+ .byte 62 # DW_AT_encoding
+ .byte 11 # DW_FORM_data1
+ .byte 11 # DW_AT_byte_size
+ .byte 11 # DW_FORM_data1
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 7 # Abbreviation Code
+ .byte 52 # DW_TAG_variable
+ .byte 0 # DW_CHILDREN_no
+ .byte 71 # DW_AT_specification
+ .byte 19 # DW_FORM_ref4
+ .byte 2 # DW_AT_location
+ .byte 24 # DW_FORM_exprloc
+ .byte 110 # DW_AT_linkage_name
+ .byte 8 # DW_FORM_string
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+## This deliberately inverts the order of the specification and location
+## attributes.
+ .byte 8 # Abbreviation Code
+ .byte 52 # DW_TAG_variable
+ .byte 0 # DW_CHILDREN_no
+ .byte 2 # DW_AT_location
+ .byte 24 # DW_FORM_exprloc
+ .byte 71 # DW_AT_specification
+ .byte 19 # DW_FORM_ref4
+ .byte 110 # DW_AT_linkage_name
+ .byte 8 # DW_FORM_string
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 0 # EOM(3)
+
+ .section .debug_info,"", at progbits
+.Lcu_begin0:
+ .long .Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
+.Ldebug_info_start0:
+ .short 4 # DWARF version number
+ .long .debug_abbrev # Offset Into Abbrev. Section
+ .byte 8 # Address Size (in bytes)
+ .byte 1 # Abbrev DW_TAG_compile_unit
+ .asciz "Hand-written DWARF" # DW_AT_producer
+ .asciz "a.cc" # DW_AT_name
+ .byte 7 # Abbrev DW_TAG_variable
+ .long .LA__x-.Lcu_begin0 # DW_AT_specification
+ .byte 9 # DW_AT_location
+ .byte 3
+ .quad _ZN1A1xE
+ .asciz "_ZN1A1xE" # DW_AT_linkage_name
+ .byte 8 # Abbrev DW_TAG_variable
+ .byte 9 # DW_AT_location
+ .byte 3
+ .quad _ZN1A1yE
+ .long .LA__y-.Lcu_begin0 # DW_AT_specification
+ .asciz "_ZN1A1yE" # DW_AT_linkage_name
+ .byte 3 # Abbrev DW_TAG_structure_type
+ .asciz "A" # DW_AT_name
+ .byte 1 # DW_AT_byte_size
+.LA__x:
+ .byte 4 # Abbrev DW_TAG_member
+ .asciz "x" # DW_AT_name
+ .long .Lconst_int-.Lcu_begin0 # DW_AT_type
+ # DW_AT_declaration
+ .sleb128 147 # DW_AT_const_value
+.LA__y:
+ .byte 4 # Abbrev DW_TAG_member
+ .asciz "y" # DW_AT_name
+ .long .Lconst_int-.Lcu_begin0 # DW_AT_type
+ # DW_AT_declaration
+ .sleb128 247 # DW_AT_const_value
+ .byte 0 # End Of Children Mark
+.Lconst_int:
+ .byte 5 # Abbrev DW_TAG_const_type
+ .long .Lint-.Lcu_begin0 # DW_AT_type
+.Lint:
+ .byte 6 # Abbrev DW_TAG_base_type
+ .asciz "int" # DW_AT_name
+ .byte 5 # DW_AT_encoding
+ .byte 4 # DW_AT_byte_size
+ .byte 0 # End Of Children Mark
+.Ldebug_info_end0:
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