With gcov, is it possible to merge to .gcda files?

See UPDATE below.

I think the intended way to do this is not to combine the .gcda files directly but to create independent coverage data files using

lcov -o unittests.coverage -c -d unittests
lcov -o integrationtests.coverage -c -d integrationtests

Each coverage data then represents one "run". You can of course create separate graphs or html views. But you can also combine the data using --add-tracefile, -a for short

lcov -o total.coverage -a unittests.coverage -a integrationtests.coverage

From the total.coverage you can generate the total report, using genhtml for example.

UPDATE: I found that it is actually possible to merge .gcda files directly using gcov-tool, which unfortunately are not easily available on the Mac, so this update doesn't answer the original question.

But with gcov-tool you can even incrementally merge many set together into one:

gcov-tool merge dir1 dir -o dir
gcov-tool merge dir2 dir -o dir
gcov-tool merge dir3 dir -o dir

Although that is not documented and might be risky to rely on.

This is really fast and avoids the round-about way over lcov, which is much slower when merging many sets. Merging some 80 sets of 70 files takes under .5 second on my machine. And you can still do an lcov on the aggregated set, which also is very much faster, should you need it. I use Emacs cov-mode which uses the .gcov files directly.

See this answer for details.

Finally I managed to solve my problem by means of lcov.

Basically what I did is the following:

• Compile the application with the flags -fprofile-arcs -ftest-coverage --coverage
• Distribute the copy of the application to each node.
• Execute the application in each node in parallel. (This step generates into the application directory in the access host the coverage information)
• Let lcov make his work:
  • lcov --directory src/ --capture --output-file coverage_reports/app.info
• Generate the html output:
  • genhtml -o coverage_reports/ coverage_reports/app.info

I hope this can be of help to someone.

Since you're using lcov, you should be able to convert the gcov .gcda files into lcov files and merge them with lcov --add-tracefile.

From manpage: Add contents of tracefile. Specify several tracefiles using the -a switch to combine the coverage data contained in these files by adding up execution counts for matching test and filename combinations.