Fix non-standard implementation of DWARF 5 DW_FORM_line_strp (7.5.5)

[zadewg]

The current implementation of DW_FORM_line_strp reads into .debug_str. This form was added in DWARF 5, and the standard specifies that the string is included in the .debug_line_str section instead.

This PR fixes #348.

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[haberman]

Thanks very much for the fix. Would you be able to add a yaml2obj unit test for this in https://github.com/google/bloaty/tree/main/tests/dwarf/debug_info?

[zadewg]

Done. Interestingly, yaml2obj (at least Ubuntu LLVM version 15.0.7 ) is not happy with:

DWARF:
  debug_str:
    - fizz
  debug_line_str:        # <---- yaml2obj-15 "unknown key" error.
    - foo.c
  debug_abbrev:

I have not tried a trunk build. The alternative way of adding the section is borrowed from LLVM's own tests for DW_FORM_line_strp.

[haberman]

As of #354 we are now using a much newer yaml2obj. Want to give it another try?

[zadewg]

Sure, just did - yaml2obj from llvmorg-17.0.0-rc3 still fails to recognize debug_line_str as a valid key, the test should remain as is.