Trouble with gcovr exclusions

Question

I am running gcovr (3.3) on an out of source build like:

gcovr --root=/path/to/source --object-directory=/path/to/build

Now I want to exclude two different things from the report:

1) Any .cpp files that have "Test" in their name

--exclude='.*Test.*' does not seem to work

2) All source files in a directory (say /path/to/source/MyModule/)

--exclude='/path/to/source/MyModule/.*' does not seem to work.

--exclude-directories='/path/to/source/MyModule' also does not seem to work.

My questions

a) what is --exclude-directories for since it seems like you (should) be able to exclude a directory with the right regex passed to --exclude?

b) Any suggestions about why the --excludes do not work as expected? Perhaps these are not the right kind/style of regular expressions?

Daphnedaphnis

Answer 1

Both of these options are not well documented, so the main source of knowledge is source code.

a) what is --exclude-directories for since it seems like you (should) be able to exclude a directory with the right regex passed to --exclude?

--exclude-directories option used by gcovr to skip directories by it's name, not fullpath. It can be verified if you check the gcovr's source code. Magic is done in def link_walker(path) function:

    for root, dirs, files in os.walk(
        os.path.abspath(path), followlinks=True
    ):
        for exc in options.exclude_dirs:
            for d in dirs:
                m = exc.search(d)

According to the os.walk documentation, dirs is a list of the names of the subdirectories. E.g. to skip all directories starts with MyMod use --exclude-directories='MyMod.*'.

b) Any suggestions about why the --excludes do not work as expected? Perhaps these are not the right kind/style of regular expressions?

Your regular expression is correct. It's typical Python's regex.

To understand what is going on at --exclude option it's useful to enable -v output. With this option enabled, output should have lots of lines:

currdir      /cygdrive/f/test/path/to/source
gcov_fname   myfile.cpp.gcov
           ['        -', '    0', 'Source', 'myfile.cpp\n']
source_fname /cygdrive/f/test/path/to/source/myfile.gcda
root         /cygdrive/f/test/path/to/source
fname        /cygdrive/f/test/path/to/source/myfile.cpp
Parsing coverage data for file /cygdrive/f/test/path/to/source/myfile.cpp

This output produced by def process_gcov_data(data_fname, covdata, source_fname, options) function. If you check the source code you will see the following:

for exc in options.exclude:
    if (filtered_fname is not None and exc.match(filtered_fname)) or \
            exc.match(fname) or \
            exc.match(os.path.abspath(fname))

Exclude filter applies to fname printed above. It's the absolute filepath. Also it applies to all files which have coverage data. If file was excluded the following line should be in output (-v option required):

Excluding coverage data for file /cygdrive/f/test/path/to/source/myfile.cpp

Bick

Thanks for the explanations. Two small follow ups: 1) I still don't understand the difference between --exclude='.*/MyMod.*' and --exclude-directories='MyMod.*'? 2) Can you explain the difference between --exclude and --gcov-exclude=? – Daphnedaphnis

2) --gcov-exclude excludes gcov data files. It applied against myfile.cpp.gcov files. --exclude excludes cpp files. – Bick

but isn't there exactly one .gcov file per .cpp file? – Daphnedaphnis

Right, but some times you need to process existent gcov data with --use-gcov-files option. In this case --gcov-exclude is the only option to exclude data files. – Bick

What would be the use case for specifying --use-gcov-files? Why would you not just use --root and --object-directory like I'm doing? – Daphnedaphnis

It's used in case you don't have cpp files and only gcov data files available. – Bick

1) --exclude-directories='MyMod.*' excludes all directories starts with MyMod. --exclude='.*/MyMod.*' excludes all the .cpp files which absolute path matches this regex. If you use the second one instead of the first it can skip path/file/MyModule.cpp instead of the folder MyModule. – Bick

Sure, but you could just craft the regex to match a folder (something like --exclude='.*/MyModule/.*'), right? So I guess this is just really a helper then? I just I'm just trying to make sure I'm correctly that everything you can do with --exclude-directory you can also do with --exclude and the appropriate regex. – Daphnedaphnis

Right, it's like a helper function – Bick

how to mention multiple directories under --exlude-directories option? seems this is not working for me --exclude-directories=test,thrift.* , here I am trying to exclude test and thrift directory. – Surroundings

@RamkumarD the --exclude flag can be used multiple times: github.com/gcovr/gcovr/issues/151#issuecomment-370941127 – Husain