https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98716
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- So, seems when asan alloca_big_alignment test is built with -gdwarf-4 -flto, we have: Offset: 0x57 Length: 214 DWARF Version: 4 Prologue Length: 105 Minimum Instruction Length: 1 Maximum Ops per Instruction: 1 Initial value of 'is_stmt': 1 Line Base: -5 Line Range: 14 Opcode Base: 13 Opcodes: Opcode 1 has 0 args Opcode 2 has 1 arg Opcode 3 has 1 arg Opcode 4 has 1 arg Opcode 5 has 1 arg Opcode 6 has 0 args Opcode 7 has 0 args Opcode 8 has 0 args Opcode 9 has 1 arg Opcode 10 has 0 args Opcode 11 has 0 args Opcode 12 has 1 arg The Directory Table (offset 0x73): 1 /usr/src/gcc/gcc/testsuite/c-c++-common/asan The File Name Table (offset 0xa1): Entry Dir Time Size Name 1 1 0 0 alloca_big_alignment.c 2 0 0 0 <built-in> Line Number Statements: [0x000000ca] Set column to 56 [0x000000cc] Extended opcode 2: set Address to 0x4011f0 [0x000000d7] Special opcode 12: advance Address by 0 to 0x4011f0 and Line by 7 to 8 [0x000000d8] Set is_stmt to 0 [0x000000d9] Copy (view 1) [0x000000da] Set column to 17 [0x000000dc] Special opcode 20: advance Address by 1 to 0x4011f1 and Line by 1 to 9 [0x000000dd] Special opcode 89: advance Address by 6 to 0x4011f7 and Line by 0 to 9 [0x000000de] Set column to 56 [0x000000e0] Special opcode 130: advance Address by 9 to 0x401200 and Line by -1 to 8 [0x000000e1] Advance PC by constant 17 to 0x401211 [0x000000e2] Special opcode 47: advance Address by 3 to 0x401214 and Line by 0 to 8 [0x000000e3] Set column to 3 [0x000000e5] Set is_stmt to 1 [0x000000e6] Special opcode 90: advance Address by 6 to 0x40121a and Line by 1 to 9 [0x000000e7] Set is_stmt to 0 This is for a TU created by LTO, which in .debug_info has: <565> DW_AT_name : (indirect string, offset: 0x676): <artificial> <569> DW_AT_comp_dir : (indirect string, offset: 0x652): /usr/src/gcc/obj2/gcc/testsuite/gcc Now, with -gdwarf-5 -flto, is still has: <566> DW_AT_name : (indirect line string, offset: 0x11d): <artificial> <56a> DW_AT_comp_dir : (indirect line string, offset: 0x12a): /usr/src/gcc/obj2/gcc/testsuite/gcc but the .debug_lines part starts with: Offset: 0x57 Length: 162 DWARF Version: 5 Address size (bytes): 8 Segment selector (bytes): 0 Prologue Length: 51 Minimum Instruction Length: 1 Maximum Ops per Instruction: 1 Initial value of 'is_stmt': 1 Line Base: -5 Line Range: 14 Opcode Base: 13 Opcodes: Opcode 1 has 0 args Opcode 2 has 1 arg Opcode 3 has 1 arg Opcode 4 has 1 arg Opcode 5 has 1 arg Opcode 6 has 0 args Opcode 7 has 0 args Opcode 8 has 0 args Opcode 9 has 1 arg Opcode 10 has 0 args Opcode 11 has 0 args Opcode 12 has 1 arg The Directory Table (offset 0x79, lines 2, columns 1): Entry Name 0 (indirect line string, offset: 0x12a): /usr/src/gcc/obj2/gcc/testsuite/gcc 1 (indirect line string, offset: 0x14e): /usr/src/gcc/gcc/testsuite/c-c++-common/asan The File Name Table (offset 0x87, lines 3, columns 2): Entry Dir Name 0 0 (indirect line string, offset: 0x11d): <artificial> 1 1 (indirect line string, offset: 0x1b3): alloca_big_alignment.c 2 0 (indirect line string, offset: 0x17b): <built-in> Line Number Statements: [0x00000096] Set column to 56 [0x00000098] Extended opcode 2: set Address to 0x4011f0 [0x000000a3] Special opcode 12: advance Address by 0 to 0x4011f0 and Line by 7 to 8 [0x000000a4] Set is_stmt to 0 [0x000000a5] Copy (view 1) [0x000000a6] Set column to 17 [0x000000a8] Special opcode 20: advance Address by 1 to 0x4011f1 and Line by 1 to 9 [0x000000a9] Special opcode 89: advance Address by 6 to 0x4011f7 and Line by 0 to 9 [0x000000aa] Set column to 56 [0x000000ac] Special opcode 130: advance Address by 9 to 0x401200 and Line by -1 to 8 [0x000000ad] Advance PC by constant 17 to 0x401211 [0x000000ae] Special opcode 47: advance Address by 3 to 0x401214 and Line by 0 to 8 [0x000000af] Set column to 3 [0x000000b1] Set is_stmt to 1 [0x000000b2] Special opcode 90: advance Address by 6 to 0x40121a and Line by 1 to 9 [0x000000b3] Set is_stmt to 0 So the important difference is in that DWARF5 has the 0 entry in the filename table while DWARF4 does not. DWARF5 Table 6.4: Line number program initial state says that the initial file is 1, which means I think read_line_program in libbacktrace is incorrect for DWARF5.