Date: Fri, 30 Nov 2007 16:40:33 -0300 From: Alejandro Pulver <alepulver@FreeBSD.org> To: Kostik Belousov <kostikbel@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: dlopen: resolving external library symbols to calling program Message-ID: <20071130164033.24b430c9@deimos.mars.bsd> In-Reply-To: <20071130170201.GK83121@deviant.kiev.zoral.com.ua> References: <20071130132858.1e4290a0@deimos.mars.bsd> <20071130170201.GK83121@deviant.kiev.zoral.com.ua>
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[-- Attachment #1 --] On Fri, 30 Nov 2007 19:02:01 +0200 Kostik Belousov <kostikbel@gmail.com> wrote: > On Fri, Nov 30, 2007 at 01:28:58PM -0300, Alejandro Pulver wrote: > > Hello. > > > > When I was updating the games/deng port, I found it failed at runtime > > with the following error: > > > > % doomsday > > While opening dynamic library > > /usr/local/lib/libdropengl.so: > > /usr/local/lib/libdropengl.so: Undefined symbol "ArgExists" > > DD_InitDGL: Loading of libdropengl.so failed. > > (null). > > > > The function is defined in m_args.c which is included in both > > "doomsday" and "libdropengl.so". But nm(1) reports it as undefined for > > "libdropengl.so". Also, it is loaded with RTLD_NOW. > > > > % nm `which doomsday` | grep ArgExists > > 080d9ef0 T ArgExists > You are looking at the wrong symbol table. ELF objects have the dynamic > symbol table that is used during run-time linking, and symbol table used > by the static linker ld. The former table is shown by nm -D. > > I suspect that you need to link the doomsday binary with the > --export-dynamic flag. See the info ld for details. > > It worked, thank you very much. I am reading some books that explain the basics of COFF/ELF formats (like Write Great Code Volume 2: Thinking Low-Level, Writing High-Level), but didn't know about the dynamic symbol table. I found the following article which briefly describes it (though it's for Solaris): http://blogs.sun.com/ali/entry/inside_elf_symbol_tables Now that I remember, the games/quakeforge port had the same problem. But someone fixed it by referencing the symbol (it was only one function) with a function pointer so it got exported in the dynamic table. In this case, could that be done with "-u symbol" when linking the executable, or it isn't possible to export a symbol with linker parameters? Thanks and Best Regards, Ale [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (FreeBSD) iD8DBQFHUGcxiV05EpRcP2ERAhp0AJ9xulMK3Df79nNM4JuAbbHmCqUkRACeNJvH KO36PTc0tFLarVJ09ivNAmw= =Er4l -----END PGP SIGNATURE-----help
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