On Wed, Sep 23, 2009 at 06:48:29PM +0200, Holger Blasum wrote: > > You must note that the parent process and the child processes have the > > exact same code. In fact, the parent process is just forked. > > Ah now I understand. Well then one has a classical race condition: > the same infrastructure for storing coverage data (*.gcda files) is > used by both parent and child, and who terminates last will get the > overwrite I guess. Let me stress: I'm not sure at the moment whether that race condition is necessary or just accidental (and no-one has ever bothered to fix it). Study the gcov sources (not long and documented in the paper I linked to in yesterday's mail) - don't have patience atm to do that myself. Special things to look at is e.g. atexit() and how this is used in a forking context. > > I did not yet resolve the problem. I hope I will be able with your help. > > Fixing ideas: > (1) try renaming functions in your child (ugly, I agree, but could be automated). > Maybe first try out whether this works with a very small example. > (2) modify gcov so that that the gcda files are written in a way that if > a child with say process ID (pid) 2 has a main.c > and a parent with say pid 1 has main.c, then the data is dumped into > main.1.gcda, main.2.gcda, and modify gcov.c to sum up both > > BTW, anyone else is encouraged to comment on too (I had just been a user > of gcov too - no contributions to development). There is also a list > with gcov knowledge at the lcov project > http://ltp.sourceforge.net/coverage/lcov.php Oops, https://lists.sourceforge.net/lists/listinfo/ltp-coverage to give a more useful pointer. -- Holger
