[lldb-dev] DWZ 0.14 released

[Tom de Vries via lldb-dev]

[ Resubmitted ]

-------- Forwarded Message --------
Subject: DWZ 0.14 released
Date: Mon, 8 Mar 2021 13:43:11 +0100
From: Tom de Vries <tdevries at suse.de>
To: Jakub Jelinek <jakub at redhat.com>, Mark Wielaard <mark at klomp.org>,
Tom de Vries <tdevries at suse.de>, dwz at sourceware.org, gcc at gcc.gnu.org,
gdb at sourceware.org, lldb-dev at lists.llvm.org,
dwarf-discuss at lists.dwarfstd.org

Hi,

DWZ 0.14 has been released.

You can download dwz from the sourceware FTP server here:

        https://sourceware.org/ftp/dwz/releases/
        ftp://sourceware.org/pub/dwz/releases/

The vital stats:

  Size    md5sum                            Name
  184KiB  cf60e4a65d9cc38c7cdb366e9a29ca8e  dwz-0.14.tar.gz
  144KiB  1f1225898bd40d63041d54454fcda5b6  dwz-0.14.tar.xz

There is a web page for DWZ at:

        https://sourceware.org/dwz/

DWZ 0.14 includes the following changes and enhancements:

* DWARF 5 support. The tool now handles most of DWARF version 5
  (at least everything emitted by GCC when using -gdwarf-5).

  Not yet supported are DW_UT_type units (DWARF 4 .debug_types
  are supported), .debug_names (.gdb_index is supported) and some
  forms and sections that are only emitted by GCC when
  generating Split DWARF (DW_FORM_strx and .debug_str_offsets,
  DW_FORM_addrx and .debug_addr, DW_FORM_rnglistx and
  DW_FORM_loclistsx). https://sourceware.org/PR24726

* .debug_sup support. DWARF Supplementary Object Files
  (DWARF 5, section 7.3.6) can now be generated when using
  the --dwarf-5 option. To keep compatibility with existing DWARF
  consumers this isn't the default yet.

  Without the --dwarf-5 option instead of a .debug_sup section dwz
  will generate a .gnu_debugaltlink section and will use
  DW_FORM_GNU_strp_alt and DW_FORM_GNU_reg_alt, instead of
  DW_FORM_strp_sup and DW_FORM_ref_sup

* An experimental optimization has been added that exploits the
  One-Definition-Rule of C++.  It's enabled using the --odr option, and
  off by default.  This optimization causes struct/union/class DIEs with
  the same name to be considered equal.  The optimization can be set to
  a lower aggressiveness level using --odr-mode=basic, to possibly be
  able to workaround problems without having to switch off the
  optimization altogether.

* The clean-up of temporary files in hardlink mode has been fixed.

* The DIE limits --low-mem-die-limit <n> / -l <n> and
  --max-die-limit <n> / -L <n> can now be disabled using respectively
  -l none and -L none.  Note that -l none disables the limit, whereas
  -l 0 sets the limit to zero.

* The usage message has been:
  - updated to show that -r and -M are exclusive.
  - updated to show at -v and -? cannot be combined with other options.
  - extended to list all options in detail.
  - restyled to wrap at 80 chars.

* An option --no-import-optimize was added that switches off an
  optimization that attempts to reduce the number of
  DW_TAG_imported_unit DIEs.  This can be used f.i. in case the
  optimization takes too long.

* A heuristic has been added that claims more memory earlier (without
  increasing the peak memory usage) to improve compression time.

* A heuristic has been added that estimates whether one of the two DIE
  limits will be hit.  If so, it will do an exact DIE count to verify
  this.  If the exact DIE count finds that the low-mem DIE limit is
  indeed hit, processing is done in low-mem mode from the start, rather
  than processing in regular mode first.  If the exact DIE count finds
  that the max DIE limit is indeed hit, processing is skipped
  altogether.

* Various other performance improvements.

* A case where previously we would either hit the assertion
  "dwz: dwz.c:9461: write_die: Assertion `refd != NULL' failed" (in
  regular mode) or a segmentation fault (in low-mem mode), now is
  handled by "dwz: Couldn't find DIE at DW_FORM_ref_addr offset 0x<n>".

* A case where a reference from a partial unit to a compile unit was
  generated has been fixed.  This could happen if a DIE was referenced
  using a CU-relative DWARF operator.

* A case has been fixed for low-mem mode where instead of issuing
  "dwz: Couldn't find DIE referenced by  DW_OP_GNU_implicit_pointer" dwz
  would run into a segfault instead.

* A multi-file case where we run into ".debug_line reference above end
  of section" has been fixed.

* The following assertion failures were fixed:
  - dwz: dwz.c:9310: write_die: Assertion `
      value && refdcu->cu_kind != CU_ALT
    ' failed.
  - dwz: dwz.c:9920: recompute_abbrevs: Assertion `
      off == cu_size
    ' failed.

* The assert condition of this assertion has been fixed:
  - write_types: Assertion `ref && ref->die_dup == NULL'.