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Osm2pgsql contribution guidelines


We operate the "Fork & Pull" model explained at

You should fork the project into your own repo, create a topic branch there and then make one or more pull requests back to the openstreetmap repository. Your pull requests will then be reviewed and discussed.


To understand the osm2pgsql code, it helps to know some history on it. Osm2pgsql was written in C in 2007 as a port of an older Python utility. In 2014 it was ported to C++ by MapQuest and the last C version was released as 0.86.0. In it's time, it has had varying contribution activity, including times with no maintainer or active developers.

Parts of the codebase still clearly show their C origin and could use rewriting in modern C++, making use of data structures in the standard library.


Osm2pgsql uses semantic versioning.

Bugs and known issues are fixed on the main branch only. Exceptions may be made for severe bugs.

Code style

Code must be written in the K&R 1TBS style with 4 spaces indentation. Tabs should never be used in the C++ code. Braces must always be used for code blocks, even one-liners.

Names should use underscores, not camel case, with class/struct names ending in _t. Template parameters must use all upper case.

Headers should be included in the order C++ standard library headers, C library headers, Boost headers, and last osm2pgsql files.

There is a .clang-format configuration available and all code must be run through clang-format before submitting. You can use git-clang-format after staging all your changes:

git-clang-format src/*pp tests/*pp

clang-format 7 or later is required.

Comments in code should follow the Doxygen convention using backslashes (not @-signs) for commands.


User documentation is available on the website, some is stored in docs/. Pages on the OpenStreetMap wiki are known to be unreliable and outdated.

The man pages for osm2pgsql and osm2pgsql-replication can be built from source with make man.

They need pandoc and argparse-manpage for the conversion. These tools can be installed with:

sudo apt-get install pandoc python3-argparse-manpage

Results should be checked into the repository.

Platforms targeted

Ideally osm2pgsql should compile on Linux, OS X, FreeBSD and Windows. It is actively tested on Debian, Ubuntu and FreeBSD by the maintainers.


The code comes with a suite of tests. They are only compiled and run when BUILD_TESTS=ON is set in the CMake config.

Tests are executed by calling ctest. You can call ctest with -L NoDB to only run tests that don't need a database.

Most of these tests depend on being able to set up a database and run osm2pgsql against it. This is most easily done using pg_virtualenv. Just run

pg_virtualenv ctest

pg_virtualenv creates a separate postgres server instance. The test databases are created in this instance and the complete server is destroyed after the tests are finished. ctest also calls appropriate fixtures that create the separate tablespace required for some tests.

When running without pg_virtualenv, you need to ensure that PostgreSQL is running and that your user is a superuser of that system. You also need to create an appropriate test tablespace manually. To do that, run:

sudo -u postgres createuser -s $USER
sudo mkdir -p /tmp/psql-tablespace
sudo chown postgres.postgres /tmp/psql-tablespace
psql -c "CREATE TABLESPACE tablespacetest LOCATION '/tmp/psql-tablespace'" postgres

Once this is all set up, all the tests should run (no SKIPs), and pass (no FAILs). If you find something which seems to be a bug, please check to see if it is a known issue at and, if it's not already known, report it there.

If you have failing tests and want to look at the test database to figure out what's happening, you can set the environment variable OSM2PGSQL_KEEP_TEST_DB to anything. This will disable the database cleanup at the end of the test. This will often be used together with the -s option of pg_virtualenv which drops you into a shell after a failed test where you can still access the database created by pg_virtualenv.

Performance testing

If performance testing with a full planet import is required, indicate what needs testing in a pull request.

BDD testing

Tests in the tests/bdd directory use behave, a Python implementation of a behaviour-driven test framework. To run the BDD tests you need to have behave and psycopg2 installed. On Ubuntu run:

sudo apt-get install python3-psycopg2 python3-behave

There are ctest directives to run the tests. If you want to run the tests manually, for example to run single tests during development, you can switch to the bdd test directory and run behave directly from there:

cd osm2pgsql/tests/bdd
behave -DBINARY=<your build directory>/osm2pgsql

Per default, behave assumes that the build directory is under osm2pgsql/build. If your setup works like that, you can leave out the -D parameter.

To make this a bit easier a shell script run-behave is provided in your build directory which sets those correct paths and calls behave. If run with -p as first option it will wrap the call to behave in a call to pg_virtualenv for your convenience. All other command line parameters of run-behave will be passed through to behave.

To run a single test, simply add the name of the test file, followed by a column and the line number of the test:

behave flex/area.feature:71

If you need to inspect the database that a test produces, you can add -DKEEP_TEST_DB and behave won't remove the database after the test is finished. This makes of course only sense, when running a single test. When running under pg_virtualenv, don't forget to keep the virtual environment as well. You can use the handy -s switch:

pg_virtualenv -s behave -DKEEP_TEST_DB flex/area.feature:71

It drops you into a shell when the behave test fails, where you can use psql to look at the database. Or start a shell in the virtual environment with pg_virtualenv bash and run behave from there.

The BDDs automatically detect if osm2pgsql was compiled with Lua and proj support and skip tests accordingly. They also check for the test tablespace tablespacetest for tests that need tablespaces.

Coverage reports

To create coverage reports, set BUILD_COVERAGE in the CMake config to ON, compile and run the tests. Then run make coverage. This will generate a coverage report in coverage/index.html in the build directory.

For this to work you need a coverage tool installed. For GCC this is gcov, for Clang this is llvm-cov in the right version. CMake will automatically try to find the correct tool. In any case the tool gcovr is used to create the report.

Releasing a new version

  • Decide on a new version. (See semantic versioning.)
  • Update version in CMakeLists.txt, look for project function.
  • Build man page (make man) and copy it to docs/osm2pgsql.1.
  • Tag release with release notes in commit message and upload the tag to Github.
  • Fill out release notes on Github.
  • Copy Windows binaries and source tarball to
  • Add release info to
  • Publish release notes as News article on


The current maintainers of osm2pgsql are Sarah Hoffmann and Paul Norman.