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[LLDB] Re-land: Use path relative to binary for finding .dwo files.
DWARF allows .dwo file paths to be relative rather than absolute. When they are relative, DWARF uses DW_AT_comp_dir to find the .dwo file. DW_AT_comp_dir can also be relative, making the entire search patch for the .dwo file relative. In this case, LLDB currently searches relative to its current working directory, i.e. the directory from which the debugger was launched. This is not right, as the compiler, which generated the relative paths, can have no idea where the debugger will be launched. The correct thing is to search relative to the location of the executable binary. That is what this patch does. Differential Revision: https://reviews.llvm.org/D97786
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‎lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

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@@ -1651,6 +1651,13 @@ SymbolFileDWARF::GetDwoSymbolFileForCompileUnit(
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return nullptr;
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dwo_file.SetFile(comp_dir, FileSpec::Style::native);
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if (dwo_file.IsRelative()) {
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// if DW_AT_comp_dir is relative, it should be relative to the location
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// of the executable, not to the location from which the debugger was
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// launched.
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dwo_file.PrependPathComponent(
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m_objfile_sp->GetFileSpec().GetDirectory().GetStringRef());
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}
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FileSystem::Instance().Resolve(dwo_file);
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dwo_file.AppendPathComponent(dwo_name);
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}

‎lldb/test/Shell/SymbolFile/DWARF/dwo-relative-path.s

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# Test to verify LLDB searches for dwos with relative paths relative to the
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# binary location, not relative to LLDB's launch location.
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# RUN: llvm-mc --filetype=obj --triple x86_64-pc-linux %s -o %t.o
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# RUN: llvm-objcopy --split-dwo=%T/dwo-relative-path.dwo %t.o
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# RUN: cd ../..
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# RUN: %lldb %t.o -o "target var x" -b 2>&1 | FileCheck %s
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# CHECK: x = 10
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.file "dwo-relative-path.cpp"
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.file 0 "." "dwo-relative-path.cpp" md5 0xadc61d242247514c5d402d62db34b825
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.type x,@object # @x
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.data
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.globl x
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.p2align 2
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x:
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.long 10 # 0xa
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.size x, 4
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.section .debug_abbrev,"",@progbits
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.byte 1 # Abbreviation Code
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.byte 74 # DW_TAG_skeleton_unit
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.byte 0 # DW_CHILDREN_no
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.byte 16 # DW_AT_stmt_list
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.byte 23 # DW_FORM_sec_offset
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.byte 114 # DW_AT_str_offsets_base
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.byte 23 # DW_FORM_sec_offset
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.byte 27 # DW_AT_comp_dir
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.byte 37 # DW_FORM_strx1
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.ascii "\264B" # DW_AT_GNU_pubnames
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.byte 25 # DW_FORM_flag_present
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.byte 118 # DW_AT_dwo_name
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.byte 37 # DW_FORM_strx1
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.byte 115 # DW_AT_addr_base
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.byte 23 # DW_FORM_sec_offset
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.byte 0 # EOM(1)
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.byte 0 # EOM(2)
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.byte 0 # EOM(3)
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.section .debug_info,"",@progbits
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.Lcu_begin0:
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.long .Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
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.Ldebug_info_start0:
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.short 5 # DWARF version number
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.byte 4 # DWARF Unit Type
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.byte 8 # Address Size (in bytes)
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.long .debug_abbrev # Offset Into Abbrev. Section
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.quad 3752513468363206953
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.byte 1 # Abbrev [1] 0x14:0x14 DW_TAG_skeleton_unit
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.long .Lline_table_start0 # DW_AT_stmt_list
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.long .Lstr_offsets_base0 # DW_AT_str_offsets_base
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.byte 0 # DW_AT_comp_dir
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# DW_AT_GNU_pubnames
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.byte 1 # DW_AT_dwo_name
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.long .Laddr_table_base0 # DW_AT_addr_base
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.Ldebug_info_end0:
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.section .debug_str_offsets,"",@progbits
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.long 12 # Length of String Offsets Set
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.short 5
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.short 0
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.Lstr_offsets_base0:
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.section .debug_str,"MS",@progbits,1
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.Lskel_string0:
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.asciz "." # string offset=0
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.Lskel_string1:
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.asciz "dwo-relative-path.dwo" # string offset=2
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.section .debug_str_offsets,"",@progbits
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.long .Lskel_string0
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.long .Lskel_string1
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.section .debug_str_offsets.dwo,"e",@progbits
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.long 24 # Length of String Offsets Set
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.short 5
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.short 0
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.section .debug_str.dwo,"eMS",@progbits,1
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.Linfo_string0:
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.asciz "x"
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.Linfo_string1:
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.asciz "int"
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.Linfo_string2:
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.asciz "clang version 13.0.0 (https://chromium.googlesource.com/external/github.com/llvm/llvm-project 6666e0d7a29c639df7a1652b6d3bf16f28edd45a)"
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.Linfo_string3:
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.asciz "dwo-relative-path.cpp"
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.Linfo_string10:
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.asciz "dwo-relative-path.dwo"
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.section .debug_str_offsets.dwo,"e",@progbits
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.long .Linfo_string0-.debug_str.dwo
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.long .Linfo_string1-.debug_str.dwo
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.long .Linfo_string2-.debug_str.dwo
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.long .Linfo_string3-.debug_str.dwo
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.section .debug_info.dwo,"e",@progbits
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.long .Ldebug_info_dwo_end0-.Ldebug_info_dwo_start0 # Length of Unit
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.Ldebug_info_dwo_start0:
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.short 5 # DWARF version number
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.byte 5 # DWARF Unit Type
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.byte 8 # Address Size (in bytes)
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.long 0 # Offset Into Abbrev. Section
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.quad 3752513468363206953
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.byte 1 # Abbrev [1] 0x14:0x65 DW_TAG_compile_unit
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.byte 8 # DW_AT_producer
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.short 33 # DW_AT_language
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.byte 9 # DW_AT_name
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.byte 10 # DW_AT_dwo_name
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.byte 2 # Abbrev [2] 0x1a:0xb DW_TAG_variable
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.byte 0 # DW_AT_name
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.long 37 # DW_AT_type
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# DW_AT_external
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.byte 0 # DW_AT_decl_file
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.byte 11 # DW_AT_decl_line
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.byte 2 # DW_AT_location
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.byte 161
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.byte 0
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.byte 3 # Abbrev [3] 0x25:0x4 DW_TAG_base_type
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.byte 1 # DW_AT_name
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.byte 5 # DW_AT_encoding
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.byte 4 # DW_AT_byte_size
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.byte 0 # End Of Children Mark
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.Ldebug_info_dwo_end0:
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.section .debug_abbrev.dwo,"e",@progbits
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.byte 1 # Abbreviation Code
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.byte 17 # DW_TAG_compile_unit
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.byte 1 # DW_CHILDREN_yes
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.byte 37 # DW_AT_producer
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.byte 37 # DW_FORM_strx1
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.byte 19 # DW_AT_language
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.byte 5 # DW_FORM_data2
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.byte 3 # DW_AT_name
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.byte 37 # DW_FORM_strx1
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.byte 118 # DW_AT_dwo_name
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.byte 37 # DW_FORM_strx1
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.byte 0 # EOM(1)
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.byte 0 # EOM(2)
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.byte 2 # Abbreviation Code
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.byte 52 # DW_TAG_variable
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.byte 0 # DW_CHILDREN_no
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.byte 3 # DW_AT_name
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.byte 37 # DW_FORM_strx1
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.byte 73 # DW_AT_type
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.byte 19 # DW_FORM_ref4
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.byte 63 # DW_AT_external
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.byte 25 # DW_FORM_flag_present
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.byte 58 # DW_AT_decl_file
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.byte 11 # DW_FORM_data1
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.byte 59 # DW_AT_decl_line
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.byte 11 # DW_FORM_data1
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.byte 2 # DW_AT_location
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.byte 24 # DW_FORM_exprloc
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.byte 0 # EOM(1)
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.byte 0 # EOM(2)
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.byte 3 # Abbreviation Code
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.byte 36 # DW_TAG_base_type
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.byte 0 # DW_CHILDREN_no
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.byte 3 # DW_AT_name
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.byte 37 # DW_FORM_strx1
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.byte 62 # DW_AT_encoding
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.byte 11 # DW_FORM_data1
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.byte 11 # DW_AT_byte_size
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.byte 11 # DW_FORM_data1
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.byte 0 # EOM(1)
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.byte 0 # EOM(2)
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.byte 0 # EOM(3)
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.section .debug_addr,"",@progbits
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.long .Ldebug_addr_end0-.Ldebug_addr_start0 # Length of contribution
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.Ldebug_addr_start0:
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.short 5 # DWARF version number
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.byte 8 # Address size
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.byte 0 # Segment selector size
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.Laddr_table_base0:
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.quad x
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.Ldebug_addr_end0:
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.section .debug_line,"",@progbits
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.Lline_table_start0:

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