systemd/README-gcov_for_udev

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Using GCC's code coverage tool, gcov, with udev

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For more information on using gcov please see:

http://gcc.gnu.org/onlinedocs/gcc/Gcov.html

With that said, here is how to get code coverage analysis for udev files.
Note that this was developed with udev version 024.

- Make sure you've installed udev and that it is working properly.
  If you are having problems, refer to the README and HOWTO-udev_for_dev
  documents in udev tarball.  I've also compiled a udev_for_dev
  toubleshooting document for Red Hat which can be found in:

  docs/rh_udev_for_dev.txt

- execute make_gcov.sh from udev top level directory

    ./make_gcov.sh

  This will compile udev with gcov support.  Basically make_gcov.sh will
  run make but override the CFLAGS.  It strips any optimization from
  CFLAGS in order for gcov to get correct code coverage analysis.  It will
  also add the -fprofile-arcs and -ftest-coverage options which are the
  necessary flags needed to use gcov.

  make_gcov.sh will assume the same default parameters as the regular
  make but also accepts the same parameters.  For example if you want
  to get code coverage analysis for udev with the DEBUG flag turned
  on, you would just execute:

    ./make_gcov.sh DEBUG=true

  There is one exception, gcov will not work with klibc as it does not
  compile cleanly with the -fprofile-arcs and -ftest-coverage flags.
  With this said it is pretty much useless to set the KERNEL_DIR flag
  when using make_gcov.sh as well.

  Don't be alarmed if you look into your udev directory and see that it
  has been polluted with a bunch of *.bb, *.bbg, *.da, and *.gcov files.
  gcov creates and uses these files to extract the code coverage info.

- After running make_gcov.sh you need to install udev again.  So basically,

    su to root
    make install

- Then execute some udev tasks.  You can run some udev tests, reboot, or
  do anything your little udev heart desires.  Once you are satisfied, you
  can now see how much udev code was covered.  I personally recommend just
  running test/udev-test.pl for starters.

- To get the udev code coverage analysis, execute run_gcov.sh from udev top
  level directory.  You need to be root to do this.

    su to root
    ./run_gcov.sh

- This creates udev_gcov.txt in the udev top level directory which holds all
  the code coverage information. To see an example of the code coverage info
  after executing the udev-test.pl test, please see:

  http://developer.osdl.org/ogasawara/gcov_for_udev/udev_gcov.txt

- Also, after having executed gcov on udev (ie executing run_gcov.sh) a
  *.gcov file is created for every file which contained code that was
  used.  Looking at the *.gcov files, one will see what lines of code
  were hit, and what lines were missed.  For, example if code in udev-add.c
  were executed, gcov then created a file called udev-add.c.gcov.  And a
  portion of udev-add.c.gov might look like:

  static int get_major_minor(struct sysfs_class_device *class_dev, struct udevice *udev)
          95    {
          95    	struct sysfs_attribute *attr = NULL;
		
          95    	attr = sysfs_get_classdev_attr(class_dev, "dev");
          95    	if (attr == NULL)
      ######    		goto error;
			dbg("dev='%s'", attr->value);
		
          95    	if (sscanf(attr->value, "%u:%u", &udev->major, &udev->minor) != 2)
      ######    		goto error;
			dbg("found major=%d, minor=%d", udev->major, udev->minor);
		
          95    	return 0;
		error:
      ######    	return -1;
		}

  Any line of code that is preceded by a "######" implies that the code
  was never hit during execution.

- Once you are done with using gcov for udev and want to return to your
  normal use of udev.  Simply,

    ./make_gcov.sh clean

  This will clean out all the *.bb, *.bbg, *.da, *.gcov files produced by gcov.
  It will also run a regular make clean on your udev directory.  Then just run
  a regular make and make install and you are back to normal:

    make
    su to root
    make isntall