On Thu, Nov 13, 2008 at 09:00:21AM +0100, Markus Hoenicka wrote: > Quoting Jeremy Chadwick <[EMAIL PROTECTED]>: > >> I know that the .so's you're loading with dlopen() need to be built a >> specific way/with certain arguments, otherwise they won't work (I >> believe what I saw was dlsym() returning NULL). My symbol names were >> getting stomped on, and there was a compiler flag that addressed that. > > Is that a BSD-specific problem? As mentioned previously, I don't run > into trouble on other platforms. Is there any documentation available > which tells me how to build a dlopen()'able object in a portable way?
I wouldn't classify is as a problem in any way, and I cannot imagine it's specific to BSD; I'm much more inclined to believe it's specific to gcc. When I looked at the resulting symbol names using nm or objdump, certain characters were prepended to them. There's a gcc or ld flag which disables this behaviour. I'll have to dig around to remind myself what it is. Once I read about it, it made perfect sense. Again, if you want me to write some code and provide some output of what I'm talking about, I can do so. >>> function_pointer = dlsym(RTLD_DEFAULT, "function_name"); >>> >>> Why is that? Or rather: what am I doing wrong? >> >> This code right here is *completely* wrong. RTLD_DEFAULT is a mode bit >> for dlopen(). I'm willing to bet a strict set of warnings would > > Citing the FreeBSD dlsym(3) man page: > > "If dlsym is called with the special handle RTLD_DEFAULT, the search > for the symbol follows the algorithm used for resolving undefined symbols > when objects are loaded." > > You probably had RTLD_LAZY and RTLD_NOW in mind which are dlopen() > flags. BTW RTLD_NEXT works just as well instead of RTLD_DEFAULT. You are right -- I missed that part of the man page, and I was most definitely thinking of RTLD_LAZY and RTLD_NOW. I cannot explain the behaviour using dlsym(RTLD_DEFAULT, ...). -- | Jeremy Chadwick jdc at parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB | _______________________________________________ email@example.com mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"