DepOwl

A practical tool helping users prevent compatibility failures.

---

HOWTO

Prepare libraries

The directory library/ provides an example of how to organize the libraries, including zlib and glib (used in the motivating examples in the paper).

Generate json files

We need to generate json files to specify the available versions of the libraries. The files are further required by abi-tracker to perform backward incompatibility checking.

python py/generate_json.py -l zlib
python py/generate_json.py -l glib

The step will generate the directory json/, where each library has two json files, e.g., zlib-asc.json and zlib-desc.json for zlib. The two json files include the versions in an ascending and descending orders, respectively.

Build libraries

DepOwl provides a script to compile history versions of the libraries. This script successfully compiles the libraries in Ubuntu 18.04 with gcc-5.5.

python py/build_lib.py -l zlib
python py/build_lib.py -l glib

If the script fails, please manually compile the libraries with debug symbol, and install the binaries in the directory build/library/version (e.g. build/zlib/1.2.5.1).

Detect incompatible library changes

DepOwl uses abi-tracker to detect incompatible library changes. A convinent method to install the tool is to use the installer provided by the abi-tracker developers. Moreover, abi-tracker requires Universal Ctags. As abi-tracker reports results in webpages, it is a bit hard to parse the results. Thus, we change the output format into xml:

--- abi-tracker:2900    my $CompatOpt = "-bin -bin-report-path \"$BinReport\"";
+++ abi-tracker:2900    my $CompatOpt = "-xml -bin -bin-report-path \"$BinReport\"";

We may also need to escape the following left brace to let perl happy:

--- abi-dumper:3200    $N=~s/(\w){/$1 {/g;
+++ abi-dumper:3200    $N=~s/(\w)\{/$1 {/g;

Then, we can use abi-tracker:

abi-tracker -build json/zlib-asc.json
abi-tracker -build json/zlib-desc.json
abi-tracker -build json/glib-asc.json
abi-tracker -build json/glib-desc.json

abi-tracker outputs results in the directory compat_report/, DepOwl provides a script to parse the results:

python py/extract_report.py

This command will generate the excel file symbols.xlsx, which contains the interested library changes required by DepOwl.

Detect potential depbugs (the filtering phase)

In this step, DepOwl selects all packages (from the given repository) that may potentially be affected by the above library changes.

python py/match_pkg.py

This step will generate the directory packages/, which contains the packages (downloaded by DepOwl) that are depended on the libraries (e.g., zlib or glib). Also, DepOwl outputs the database file depbug.db, which contains the potential depbugs (in the table potential_depbug).

The above command works on a test repository. Make the following change to run on the real-word repository shipped with ubuntu-19.10 (unzip repository/ubuntu-19.10.zip first, it may takes a long time to download the packages):

--- py/match_pkg.py:159    for pkg_file_name in glob.glob('repository/test/*.txt'):
+++ py/match_pkg.py:159    for pkg_file_name in glob.glob('repository/ubuntu-19.10/*.txt'):

Confirm depbugs (the determining phase)

When analyzing application binaries (with debug symbols), extract API usages:

cd src

//Step 1: install clang, and compile the target file test.c
sudo apt install clang-9 llvm-9
clang-9 -S -emit-llvm -g -O -Xclang -femit-debug-entry-values -o test.ll test.c
llc-9 test.ll -o test.o -filetype=obj

//Step 2: install libdwarf, compile, and run the program
sudo apt install libdwarf-dev
gcc get_decl.c -ldwarf -o get_decl
./get_decl test.o

When taking source code as input, we need to get the source code:

python py/download_source.py

This command will generate the directory sources/, which contains the source code for each package.

Then, DepOwl analyze the source code by using srcML:

python py/src2srcml.py

This command transfers the source code to xml files located in the directory xml/.

Finally, DepOwl confirms depbugs by:

python py/confirm_symbol.py 2>/dev/null

The results are located in the table confirmed_depbug.

The depbugs may have duplicates. The follosing commands can deduplicate the results:

sqlite3 depbug.db

sqlite> .headers ON
sqlite> .mode column
sqlite> select distinct PkgName,PkgVer,Depname,DepVer,PostVer as BugVer
   ...> from confirmed_depbug;

PkgName     PkgVer      Depname     DepVer      BugVer    
----------  ----------  ----------  ----------  ----------
ccache      3.7.3-1     zlib1g      >= 1:1.1.4  1.2.5.2   
cockpit-br  202.1-1     libglib2.0  >= 2.37.6   2.39.1    
homebank    5.2.2-1     libglib2.0  >= 2.37.3   2.39.1    
mathgl      2.4.4-4     zlib1g      >= 1:1.2.0  1.2.5.2   

That's it, have fun.