On Wed, Jun 25, 2014 at 11:32 AM, Cristian Rodríguez <crrodrig...@opensuse.org> wrote: > El 25/06/14 13:00, Luis R. Rodriguez escribió: >> On Wed, Jun 25, 2014 at 9:45 AM, Cristian Rodríguez >> <crrodrig...@opensuse.org> wrote: >>> El 12/06/14 21:04, Luis R. Rodriguez escribió: >>> >>>> - If you want to use the dynamic link loader you should use >>>> AX_AVAILABLE_SYSTEMD() but must then ensure to use -rdynamic -ldl >>>> when linking, if using automake autotools will deal with this for >>>> you, >>>> otherwise you must ensure this is in place on your Makefile. >>> >>> I urge you not to do that, this is unsuitable for distributions in a >>> number of ways. >>> >>> - RPM does not handle this kind of dependencies. >>> >>> - Applications must only dlopen stuff they have control of, like..the X >>> server loading its drivers, PHP loading its modules, apache loading >>> mod_ssl.. etc.. dlopening system libraries like libsystemd-whatever is a >>> no-no.. applications that do this constantly break, are a pain in the >>> ass to maintain. I have been fighting with this madness for years. >> >> Thanks for the details! When I looked into this I didn't find any of >> the issues you have laid out, any chance you have pointers to a full >> fledged rant and technical details? I'd like to include it on my code >> and documentation :) > > As usual, there is no documentation, this is my experience while dealing > moutains of build failures and dependency issues in openSUSE.
A really nice public rant can help :) but so can editing the upstream dlopen() man pages: https://www.kernel.org/doc/man-pages/download.html If I would have found some good technical information on issues with dlopen() I wouldn't have even bothered, but I do think it can help prevent more folks from even considering it seriously. > About the first point, rpm does not add dlopen() libraries as > "Requires", packagers must either add an explicit recommends or requires > on a versioned shared library to the rpm spec, this fails in a number of > ways: > > - Adding explicit Requires to libraries is forbidden by policy, rpmlint > may warn and in some cases error out. > > - Even if you go ahead with that, there is no warranty that the library > version will stay the same from product to product..requiring frequent > adjustments, ifs and buts in the spec file. > > - Everytime the library major version changes, your code will fail, even > in the case the library provides the same interface. > > _ Unless you use an specific glibc facility, DL_CALL_FCT() you cannot > LD_PROFILE the application correctly.. > > There are other less obvious ways things can go wrong..such as obscure > initialization order bugs when dependencies down the chain use GCC > constructors/destructors but that's all in the top of my head for now. Fun :) yeah this would be good to have well documented somewhere. Luis _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
