> Now that you mention it, turning on "-W -Wall -fstrict-aliasing" does > give a warning about "dereferencing type-punned pointer will break > strict-aliasing rules" (but not if I don't turn on -W -Wall) ... for > some reason I always thought "-W -Wall" warned about everything > regardless of optimiser settings ... chalk one up to experience I guess! You should be able to use -Wstrict-aliasing as well. > Yup ... I'm not sure what the alternative is though given at the end of > the day this has to go through htonl/ntohl in preparation for network > transmission and I'm not aware of any word-length-transparent way of > doing THAT ... of course, it's possibly more due to my ignorance than > there actually not being a way, if there is I'd be most happy to find > out! :-) Someone should correct me, but if you really have to go through a long generically, I don't see why you couldn't go through an unsigned int first. Then push the unsigned int into the lower 4-bytes of the unsigned long and then reverse it coming back. I don't know if your system allows for any such consistency. > I could and will probably end up doing that ultimately ... I just was of > the impression that the sort of casting I was using was reasonably > widely accepted and was a little confused when it worked fine up until > when I tried compiling it on a GCC 4.x system (at which point it gave me > random stack-corrupting segfaults - always a pain to debug!) ... ah well I don't know the changes there but the -fstrict-aliasing option has been enabled in -O2 for a while. If warnings were surpressed then the problem was just hidden for a while. > ... I notice this sort of casting in a few other libraries I use - and > I've just found that their autoconf'd makefiles all seem to have > -fno-strict-aliasing in them so I might just do that for now so I can > actually get some results! If you're developing a library with external headers, be careful about what type of aliasing you put into functoins defined in a header since they might not be used in a program compiled without strict aliasing. corey
