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libdwarf README.md

This is libdwarf README[.md]

Updated 6 November 2022

ci runs builds on Linux, Freebsd, msys2, and MacOS using configure,cmake, and meson.

ci

Version 0.4.2 released 13 September 2022 Versions before 0.4.2 had problems in the test suite so make check or ninja test might fail on some tests (sorry).

Version 0.5.0 is not released.

REQUIREMENTS from a libdwarf.tar.xz

Mentioning some that might not be automatically in your base OS release. Restricting attention here to just building libdwarf and dwarfdump.

If the objects you work with do not have section content compressed with zlib(libz) or libzstd neither those libraries nor their header files are required for building/using libdwarf/dwarfdump.

Ubuntu: 
sudo apt install pkgconf zlib1g zlib1g-dev libzstd1
# Use of libzstd1 is new in 0.4.3
# zlib1g zlib1g-dev libzstd1 are all optional but
# are required to read any DWARF data in compressed
# sections.
optional add: cmake meson ninja doxygen 

FreeBSD:
pkg install bash python3 gmake binutils pkgconf lzlib zstd 
# libzstd is likely in /usr/local/lib and zstd.h
# in /usr/local/include and the compiler will not look there
# by default. All will still build fine without it and
# without lzib too, though compressed DWARF sections
# may not be readable.
# lzlib zstd all optional, but needed to read compressed
# DWARF sections. 
optional add: cmake meson ninja doxygen

Ensure that all the needed programs are in $PATH,
including python3.

BUILDING from a libdwarf.tar.xz

This is always recommended as it's not necessary to have GNU autotools installed. These examples show doing a build in a directory different than the source as that is generally recommended practice.

GNU configure/autotools build

Note: if you get a build failure that mentions something about test/ and missing .Po object files add --disable-dependency-tracking to the configure command.

rm -rf /tmp/build
mkdir /tmp/build
cd /tmp
tar xf <path to>/libdwarf-0.4.2.tar.xz
cd  /tmp/build
/tmp/libdwarf-0.4.2/configure
make
make check

cmake build

README.cmake has details on the available cmake options.

We suggest that you will find meson a more satisfactory tool.

meson build

meson 0.45.1  on Ubuntu 18.04 fails.
meson 0.55.2  on Ubuntu 20.04 works.
meson 0.60.3  on Freebsd 12.2 and Freebsd 13.0 works.

See README.cmake for the mingw64 msys2 packages to install and the command(s) to do that in msys2. The tools listed there are also for msys2 meson and autotools/configure.

The msys2 meson ninja install not only installs libdwarf-0.dll and dwarfdump.exe it updates the executables in the build tree linking to that dll so all such executables in the build tree work too.

For example (all build environments):

meson /tmp/libdwarf-0.4.2
ninja
ninja install
ninja test

For a faster build, adding additional checks:

export CFLAGS="-g -pipe"
export CXXFLAGS="-g -pipe"
meson /tmp/libdwarf-0.4.2 -Ddwarfexample=true 
ninja -j8
ninja install
ninja test

BUILDING on linux from a git clone with configure/autotools

Ignore this section if using meson (or cmake).

This is not recommended as it requires you have GNU autotools and pkg-config installed. Here we assume the source is in a directory named /path/to/code

For example, on Ubuntu 20.04 sudo apt-get install autoconf libtool pkg-config

Note: if you get a build failure that mentions something about test/ and missing .Po object files add --disable-dependency-tracking to the configure command.

Using the source/build directories from above as examples, do :

# Standard Linux Build
cd /path/to/code
sh autogen.sh
cd /tmp/build
/path/to/code/configure
make
make check

BUILDING on MacOS from a git clone configure

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
brew install autoconf automake libtool
# Then use the  Standard Linux Build lines above.

Options to meson on Linux/Unix

For the basic configuration options list , do: meson configure /path/to/code

To set options and show the resulting actual options:

# Here  just setting one option.
meson setup  -Ddwarfexample=true  .  /home/davea/dwarf/code 
meson configure .

The meson configure output is very wide (just letting you know).

Options to configure/autotools on Linux/Unix

For the full options list , do:

/path/to/code/configure --help

By default configure compiles and uses libdwarf.a. With --enable-shared appended to the configure step, both libdwarf.a and libdwarf.so are built and the runtimes built will reference libdwarf.so.

If you get a build failure that mentions something about test/ and missing .Po object files add --disable-dependency-tracking to the configure command. With that option do not assume you can alter source files and have make rebuild all necessary.

See: https://www.gnu.org/savannah-checkouts/gnu/automake/history/automake-history.html#Dependency-Tracking-Evolution

With

--enable-shared --disable-static

appended to the configure command libdwarf.so is built and used but libdwarf.a is not built.

Other options of possible interest:

--enable-wall to turn on compiler diagnostics 
--enable-dwarfexample to compile the example programs.

configure -h     shows the options available.

Sanity checking:

gcc has some checks that can be done at runtime. -fsanitize=undefined is turned on by --enable-sanitize

Options to meson on Windows (Msys2)

All libdwarf builds are automatically shared object (dll) builds. No static library libdwarf.a for installation is supported.

Has the same meson setup reporting as on Linux (above).

Options to configure on Windows (Msys2)

All libdwarf builds are automatically shared object (dll) builds. No static libdwarf.a can be installed.

Has the same meson setup reporting as on Linux (above).

Distributing via configure/autotools

When ready to create a new source distribution do a build and then

make distcheck

INCOMPATIBILITIES. Changes to interfaces

Comparing libdwarf-0.5.0 to libdwarf-0.4.2

Not released. dwarf_get_globals() is compatible but it now returns data from .debug_names in addition to .debug_pubnames (either or both could be in an object file). New function dwarf_global_tag_number() makes the data from .debug_names a bit more useful (if a library user wants it).

Comparing libdwarf-0.4.2 to libdwarf-0.4.1

No incompatibilities.

Comparing libdwarf-0.4.1 to libdwarf-0.4.0

Added a new function dwarf_suppress_debuglink_crc() which speeds up gnu debuglink (only use it if you are sure the debuglink name-check alone is sufficient).

Comparing libdwarf-0.4.0 to libdwarf-0.3.4

A few dealloc() functions changed name to have a consistent pattern for all such. Access to the DWARF5 .debug_names section is now fully implemented.

See the Recent Changes section in libdwarf.pdf (in the release).

Or see the latest online html version [dwhtml] for the details.. Or see (via download) the latest pdf html version [dwpdf].

Notice the table of contents at the right edge of the html page.

Reading DWARF from memory

If one has DWARF bytes in memory or in a kind of file system libdwarf cannot understand one should use

dwarf_object_init_b()
...call libdwarf functions...
dwarf_finish()

and create source to provide functions and data for the three struct types:

struct Dwarf_Obj_Access_Interface_a_s
struct Dwarf_Obj_Access_Methods_a_s
struct Dwarf_Obj_Access_Section_a_s

These functions and structs now seem complete (unlike the earlier libdwarf versions), hence the name and content changes.

For a worked out example of reading DWARF direct from memory with no file system involved see

src/bin/dwarfexample/jitreader.c

and see the html [dwhtml] (www.prevanders.net/libdwarfdoc/index.html).

The latest pdf is [dwpdf] (www.prevanders.net/libdwarf.pdf)

David Anderson.