Re: Generating code coverage reports

[Ludovic Courtès]

Hi,

Simon Josefsson <address@hidden> writes:

> build-coverage:
>       make CFLAGS=$(COVERAGE_OPTS) CXXFLAGS=$(COVERAGE_OPTS) VALGRIND=
>       make CFLAGS=$(COVERAGE_OPTS) CXXFLAGS=$(COVERAGE_OPTS) VALGRIND= check
>       mkdir -p doc/coverage
>       lcov --directory . --output-file doc/coverage/$(PACKAGE).info --capture

I'm not sure this is correct, because the `.gcda' files that are used as
input in the end do not summarize the code covered by every single test.
Concretely, this means that lcov's output slightly underestimates code
coverage.

Let me explain this.  Suppose you have tests T1 and T2:

  * T1 uses code from foo.c and t1.c;
  * T2 uses code from foo.c and t2.c.

Running "make check" runs T1, then T2:

  * T1 is run, producing foo.gcda and t1.gcda;
  * T2 is run, *overriding* foo.gcda and producing t2.gcda.

In the end, `lcov' is fed with foo.gcda from the T2 run, whereas what we
really want to have is the code covered in foo.c by T1 *and* T2.

Thus, after each test run, all GCDA files produced should be fed to
`lcov' (thereby producing a `.info' file) and removed; once all tests
run, all `.info' files should be aggregated (using "lcov -a"), and
finally fed to `genhtml'.

Does that make sense?

Thanks,
Ludo'.