Relax condition for DW_DLE_IMPROPER_DWO_ID

[jeremy-rifkin]

Hello,
Clang has added a flag called -gmodules where when using C++20 modules the compiler omits most DWARF info pertaining to types from object files and instead a debug fission-like link to a pcm file (used by clang for precompiled headers and modules) is used. The CU DIE looks like

0x00005309: Compile Unit: length = 0x00000021, format = DWARF32, version = 0x0005, unit_type = DW_UT_compile, abbr_offset = 0x0000, addr_size = 0x08 (next unit at 0x0000532e)

0x00005315: DW_TAG_compile_unit
              DW_AT_producer	("clang version 21.1.8 (https://github.com/conda-forge/clangdev-feedstock bd55c85b7753fc7bd9035ad4c72ca6ee803d158f)")
              DW_AT_language	(DW_LANG_C_plus_plus_14)
              DW_AT_name	("cpptrace")
              DW_AT_str_offsets_base	(0x00000008)
              DW_AT_stmt_list	(0x000007a5)
              DW_AT_comp_dir	("/path/to/my/dir")
              DW_AT_GNU_dwo_id	(0xe32a33107ad1afcc)
              DW_AT_dwo_name	("build/files/path/to/module.pcm")

There is a check in dwarf_die_deliv.c which errors when a DW_DLE_IMPROPER_DWO_ID attribute is present but dwarf 4 isn't used, or dwarf 5 and apple clang are used (this part was recently added in b0b8cea).

Since this isn't just an apple clang caveat, and I imagine gcc might do something similar in the future, I think the condition should be relaxed to just checking if the version is before dwarf 4.

[davea42]

Yes, this seems sensible.
Thanks!

[jeremy-rifkin]

Thanks so much for the quick reply and merge! This will be very helpful for enabling cpptrace to work with code compiled with -gmodules.

[davea42]

I really appreciate your thoughtful and meaningful insights. Thanks again.