Hello Yves, On Tue, May 05, 2009 at 09:46:06PM +0000, Cadieux, Yves wrote: > I have a program multi-threaded Warning: for multi-threaded programs, while gcov may give you good heuristic guidance for most things you want to do, in theory it can give you misleading numbers which might matter in a safety-critical context (see below). > and that programs is invoked multi times for my application. My questions are > 1-Will I get a .gcda file for each invocation? No. Multiple gcda files fill up existing ones. New ones are only created the first time. > 2-How can I merge the .gcda ? The design is that you don't have to: if you invoke twice, the gcda counters are added up within the gcda file. (I agree I don't spot this info in http://gcc.gnu.org/onlinedocs/gcc/Gcov.html, if you have to, doing dirty things such as interim recompiles for whatever reason: http://www.nabble.com/merge-two-.gcda-files-td22575093.html) > 3-Also sometimes I do not get the .gcda for the program file but I do get the .gcda for the objects that make the program. What am I missing. ? Iirc, you get a .gcda for each source file that makes the program. (Maybe I misunderstood.) Multithreaded: the gcov infrastructure had not been designed for multithreaded use and while useful for explorative purposes cannot guarantee even conservative numbers (because subtraction is used to interpolate intermediate results). As discussed in [1] I guess it would be easy to modify gcc/gcov in a way to get at least rid of the interpolation feature, this would come at the price of less efficiency for non-multithreaded systems though. [1] http://sysrun.haifa.il.ibm.com/hrl/greps2007/papers/gcov-on-an-embedded-system.pdf Cheers, -- Holger Blasum SYSGO AG / www.sysgo.com
