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[lldb/DWARF] Respect member layout for types parsed through declarations #110648

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Oct 2, 2024
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[lldb/DWARF] Respect member layout for types parsed through declarations #110648

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12 changes: 4 additions & 8 deletions lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2128,14 +2128,10 @@ bool DWARFASTParserClang::CompleteRecordType(const DWARFDIE &die,
TypeSystemClang::BuildIndirectFields(clang_type);
TypeSystemClang::CompleteTagDeclarationDefinition(clang_type);

if (type)
layout_info.bit_size = type->GetByteSize(nullptr).value_or(0) * 8;
if (layout_info.bit_size == 0)
layout_info.bit_size =
die.GetAttributeValueAsUnsigned(DW_AT_byte_size, 0) * 8;
if (layout_info.alignment == 0)
layout_info.alignment =
die.GetAttributeValueAsUnsigned(llvm::dwarf::DW_AT_alignment, 0) * 8;
layout_info.bit_size =
die.GetAttributeValueAsUnsigned(DW_AT_byte_size, 0) * 8;
layout_info.alignment =
die.GetAttributeValueAsUnsigned(llvm::dwarf::DW_AT_alignment, 0) * 8;

clang::CXXRecordDecl *record_decl =
m_ast.GetAsCXXRecordDecl(clang_type.GetOpaqueQualType());
Expand Down
132 changes: 132 additions & 0 deletions lldb/test/Shell/SymbolFile/DWARF/x86/DW_AT_declaration-unusual-layout.s
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Original file line number Diff line number Diff line change
@@ -0,0 +1,132 @@
## Test that lldb respects the layout defined in DWARF even when starting out
## with a declaration of the class.

# RUN: split-file %s %t
# RUN: llvm-mc --triple x86_64-pc-linux %t/asm --filetype=obj -o %t.o
# RUN: %lldb -s %t/commands -o exit %t.o 2>&1 | FileCheck %s

#--- commands
target var a -fx
# CHECK-LABEL: target var a
# CHECK: (A) a = (i = 0xbaadf00d)

#--- asm
.data
.p2align 4
.long 0
a:
.long 0xdeadbeef
.long 0xbaadf00d

.section .debug_abbrev,"",@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 0 # EOM(1)
.byte 0 # EOM(2)
.byte 2 # Abbreviation Code
.byte 52 # DW_TAG_variable
.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 2 # DW_AT_location
.byte 24 # DW_FORM_exprloc
.byte 0 # EOM(1)
.byte 0 # EOM(2)
.byte 3 # Abbreviation Code
.byte 19 # DW_TAG_structure_type
.byte 0 # DW_CHILDREN_no
.byte 3 # DW_AT_name
.byte 8 # DW_FORM_string
.byte 60 # DW_AT_declaration
.byte 25 # DW_FORM_flag_present
.byte 0 # EOM(1)
.byte 0 # EOM(2)
.byte 4 # 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 5 # 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 56 # DW_AT_data_member_location
.byte 11 # DW_FORM_data1
.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 0 # EOM(3)

.section .debug_info,"",@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 [1] DW_TAG_compile_unit
.asciz "Hand-written DWARF" # DW_AT_producer

.byte 2 # Abbrev [2] DW_TAG_variable
.asciz "a" # DW_AT_name
.long .LA_decl-.Lcu_begin0 # DW_AT_type
.byte 9 # DW_AT_location
.byte 3
.quad a
.LA_decl:
.byte 3 # Abbrev [3] DW_TAG_structure_type
.asciz "A" # DW_AT_name
# DW_AT_declaration
.byte 0 # End Of Children Mark
.Ldebug_info_end0:

.Lcu_begin1:
.long .Ldebug_info_end1-.Ldebug_info_start1 # Length of Unit
.Ldebug_info_start1:
.short 4 # DWARF version number
.long .debug_abbrev # Offset Into Abbrev. Section
.byte 8 # Address Size (in bytes)
.byte 1 # Abbrev [1] DW_TAG_compile_unit
.asciz "Hand-written DWARF" # DW_AT_producer

.byte 4 # Abbrev [4] DW_TAG_structure_type
.asciz "A" # DW_AT_name
# DW_AT_declaration
.byte 8 # DW_AT_byte_size
.byte 5 # Abbrev [5] DW_TAG_member
.asciz "i" # DW_AT_name
.long .Lint-.Lcu_begin1 # DW_AT_type
## NB: empty padding before this member
.byte 4 # DW_AT_data_member_location
.byte 0 # End Of Children Mark

.Lint:
.byte 6 # Abbrev [6] 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_end1:
3 changes: 3 additions & 0 deletions lldb/test/Shell/SymbolFile/DWARF/x86/DW_AT_declaration-with-children.s
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Original file line number Diff line number Diff line change
Expand Up @@ -105,6 +105,8 @@ c1:
.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 7 # Abbreviation Code
Expand Down Expand Up @@ -251,6 +253,7 @@ c1:
.LB1:
.byte 6 # Abbrev [6] DW_TAG_class_type
.asciz "B1" # DW_AT_name
.byte 8 # DW_AT_byte_size
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Adding this was necessary because lldb crashed without it (in llvm record layout code). Removal of the check was hiding this problem by recomputing the size without lldb's input. While this is something that we may to fix, I don't think we're likely to run into this situation (structure definition without a size attribute) outside of hyper-reduced test cases.

.byte 7 # Abbrev [5] 0x58:0xc DW_TAG_member
.asciz "ptr" # DW_AT_name
.long .LAptr # DW_AT_type
Expand Down
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