dwz - DWARF optimization and duplicate removal tool
dwz [OPTION...] [FILES]
dwz is a program that attempts to optimize DWARF debugging information contained in ELF
shared libraries and ELF executables for size, by replacing DWARF information representa-
tion with equivalent smaller representation where possible and by reducing the amount of
duplication using techniques from DWARF standard appendix E - creating DW_TAG_partial_unit
compilation units (CUs) for duplicated information and using DW_TAG_imported_unit to
import it into each CU that needs it.
The tool handles DWARF 32-bit format debugging sections of versions 2, 3 and 4 and GNU
extensions on top of those, though using DWARF 4 or worst case DWARF 3 is strongly recom-
The tool has two main modes of operation, without the -m option it attempts to optimize
DWARF debugging information in each given object (executable or shared library) individu-
ally, with the -m option it afterwards attempts to optimize even more by moving DWARF
debugging information entries (DIEs), strings and macro descriptions duplicated in more
than one object into a newly created ELF ET_REL object whose filename is given as -m
option argument. The debug sections in the executables and shared libraries specified on
the command line are then modified again, referring to the entities in the newly created
-m FILE --multifile FILE
Multifile mode. After processing all named executables and shared libraries,
attempt to create ELF object FILE and put debugging information duplicated in more
than one object there, afterwards optimize each named executable or shared library
even further if possible.
Look for executables or shared libraries hardlinked together, instead of rewriting
them individually rewrite just one of them and hardlink the rest to the first one
-M NAME --multifile-name NAME
Specify the name of the common file that should be put into the .gnu_debugaltlink
section alongside with its build ID. By default dwz puts there the argument of the
Specify that the name of the common file to be put into the .gnu_debugaltlink sec-
tion is supposed to be relative path from the directory containing the executable
or shared library to the file named in the argument of the -m option. Either -M or
-r option can be specified, but not both.
Silence up some of the most common messages.
-o FILE --output FILE
This option instructs dwz not to overwrite the specified file, but instead store
the new content into FILE. Nothing is written if dwz exits with non-zero exit
code. Can be used only with a single executable or shared library (if there are no
arguments at all, a.out is assumed).
-l COUNT --low-mem-die-limit COUNT
Handle executables or shared libraries containing more than COUNT debugging infor-
mation entries in their .debug_info section using a slower and more memory usage
friendly mode and don't attempt to optimize that object in multifile mode. The
default is 10 million DIEs. There is a risk that for very large amounts of debug-
ging information in a single shared library or executable there might not be enough
memory (especially when dwz tool is 32-bit binary, it might run out of available
virtual address space even sooner).
-L COUNT --max-die-limit COUNT
Don't attempt to optimize executables or shared libraries containing more than
COUNT DIEs at all. The default is 50 million DIEs.
Print short help and exit.
Print version number and short licensing notice and exit.
Command-line arguments should be the executables, shared libraries or their stripped to
file separate debug information objects.
$ dwz -m .dwz/foobar-1.2.debug -rh \
bin/foo.debug bin/foo2.debug foo/lib/libbar.so.debug
will attempt to optimize debugging information in bin/foo.debug, bin/foo2.debug and
lib/libbar.so.debug (by modifying the files in place) and when beneficial also will create
.dwz/foobar-1.2.debug file. .gnu_debugaltlink section in the first two files will refer
to ../.dwz/foobar-1.2.debug and in the last file to ../../.dwz/foobar-1.2.debug. If e.g.
bin/foo.debug and bin/foo2.debug were hardlinked together initially, they will be
hardlinked again and for multifile optimizations considered just as a single file rather
$ dwz -o foo.dwz foo
will not modify foo but instead store the ELF object with optimized debugging information
if successful into foo.dwz file it creates.
$ dwz *.debug foo/*.debug
will attempt to optimize debugging information in *.debug and foo/*.debug files, optimiz-
ing each file individually in place.
is equivalent to dwz a.out command.
http://dwarfstd.org/doc/DWARF4.pdf , gdb(1).
Jakub Jelinek <email@example.com>.
15 June 2012 dwz(1)