.. program is needed to resolve option links
.. program::  gcovr

.. _merging_coverage:

Merging Coverage Data
=====================

You can merge coverage data from multiple runs with
:option:`-a/--json-add-tracefile/--add-tracefile<gcovr --json-add-tracefile>`.

For each run, generate :ref:`JSON output <json_output>`:

.. code-block:: bash

    ...  # compile and run first test case
    gcovr ... --json run-1.json
    ...  # compile and run second test case
    gcovr ... --json run-2.json


Next, merge the json files and generate the desired report::

    gcovr --json-add-tracefile run-1.json --json-add-tracefile run-2.json --html-details coverage.html

You can also use unix style wildcards to merge the json files without
duplicating :option:`-a/--json-add-tracefile/--add-tracefile<gcovr --json-add-tracefile>`. With this option
you have to place your pathnames with wildcards in double quotation marks::

    gcovr --json-add-tracefile "run-*.json" --html-details coverage.html

If you want to merge coverage reports generated in different `--root` directories you
can use the :option:`--json-base` to get the same root directory for all reports.

If you have same function names defined on different line the default behavior is to abort.
With the :option:`--merge-mode-functions` you can change this:

- ``strict``: Abort if same function is defined on a different line (old behavior).
- ``merge-use-line-0``: Allow same function on different lines, in this case use line 0.
- ``merge-use-line-min``: Allow same function on different lines, in this case the minimum line.
- ``merge-use-line-max``: Allow same function on different lines, in this case use maximum line.
- ``separate``: Allow same function on different lines. Instead of merging keep the functions separate.

If you have differing number of conditions on the same line, the default behavior is to abort.
With the :option:`--merge-mode-conditions` you can change this:

- ``strict``: Abort if condition count differs for the same line (default).
- ``fold``: Narrow the conditions to match the lowest count between the two coverage counts.

.. versionadded:: 6.0

   The :option:`gcovr --json-base` option.
   The :option:`gcovr --merge-mode-functions` option.

.. versionadded:: 8.3

    The :option:`gcovr --merge-mode-conditions` option.