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DWARF 5 Standard

By DWARF Standards Committee

February 20, 2017

The DWARF Version 5 Debugging Format Standard is based on the DWARF Version 4 Standard. It is an upward compatible extension to the previous version of the standard.

The major enhancements in DWARF Version 5 are

  • Description of the objectives and rationale for the design and evolution of the DWARF Standard.
  • Merge .debug_types into .debug_info section.
  • Support collecting common debug information into a single supplementary object file.
  • Replace the line number program header allowing better data compression and source validation.
  • Support split object file and package representations to allow DWARF info to be kept separate from executable files.
  • Replace .debug_macinfo with .debug_macro representation allowing much more compact representation of C/C++ macros.
  • Replace .debug_pubnames and .debug_pubtypes with much more functional .debug_names section.
  • Replace location list (.debug_loc) and range list (.debug_ranges) sections with new sections (.debug_loclists and .debug_rnglists) allowing more compact representation and eliminating relocations.
  • Add new TAG to describe call site information, including tail call and tail recursion.
  • Improve support for FORTRAN assumend rank arrays, dynamic rank arrays, and co-arrays.
  • Add new operators which support a DWARF expression stack containing typed values.
  • Add support for C++ auto return type, deleted member functions, and defaulted constructors and destructors.
  • Add new attribute to identify a subprogram which does not return to its caller.
  • Add language codes for C 2011, C++ 2003, C++ 2011, C++ 2014, Dylan, Fortran 2003, Fortran 2008, Go, Haskell, Julia, Modula 3, Ocaml, OpenCL, Rust, Swift, and BLISS.
  • Numerous minor additions to improve functionality and performance.
The DWARF Version 5 Standard is compatible with DWARF Version 4 except as follows:
  • The compilation unit header (in the .debug_info section) has a new unit_type field.
  • New operand forms for attribute values are defined (DW_FORM_addrx*, DW_FORM_data16, DW_FORM_implicit_const, DW_FORM_line_strp, DW_FORM_loclistx, DW_FORM_rnglistx, DW_FORM_ref_sup*, DW_FORM_strp_sup and DW_FORM_strx*).
  • The line number table header is substantially revised.
  • A location list entry with the address range (0, maximum-address) is defined as the new default location list entry.
  • In a string type, the DW_AT_byte_size attribute is re-defined to always describe the size of the string type. (Previously it described the size of the optional string length data field if the DW_AT_string_length attribute was also present.)
  • New representations for macro definitions, symbol lookup, location lists and range lists.

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