Undefined characters in the erlang nif shared library

Question

I'm having trouble trying to link my shared library (erlang nif) to another shared library (libpurple) that loads other shared libraries (plugins) using dlopen.

The problem is that mylib.so links to libpurple.so, libpurple.so loads plugins.so using dlopen, and plugins.so cannot find characters from libpurple.so

1> mylib:init(). ok 2> /usr/lib/erlang/erts-6.3/bin/beam.smp: symbol lookup error: /usr/lib/purple-2/libmyspace.so: undefined symbol: purple_account_option_string_new 

I compile as:

 gcc -fPIC -shared `pkg-config --cflags --libs purple` -I /usr/lib/erlang/erts-6.3/include -o priv/mylib.so c_src/mylib.c 

It looks like the problem is with dlopen caused by erlang: load_nif, this code has the same problem as erlang nif, RTLD_NOW | RTLD_GLOBAL fixes this, but I cannot change how erlang calls dlopen ...

 #include <dlfcn.h> #include <stdio.h> #include <glib.h> void (*purple_util_set_user_dir)(const char *dir); void (*purple_debug_set_enabled)(gboolean enabled); gboolean (*purple_core_init)(const char *ui); int main() { void* lib = dlopen("/usr/lib/libpurple.so", RTLD_LAZY); purple_util_set_user_dir = dlsym(lib, "purple_util_set_user_dir"); purple_debug_set_enabled = dlsym(lib, "purple_debug_set_enabled"); purple_core_init = dlsym(lib, "purple_core_init"); purple_util_set_user_dir("/tmp/purpletest"); purple_debug_set_enabled(TRUE); purple_core_init("test"); return 0; } 

The only workaround I get is to call erlang as LD_PRELOAD=/usr/lib/libpurple.so erl , but is far from ideal.

Looks like the same problem that was solved with RTLD_GLOBAL, https://developer.pidgin.im/ticket/7872

Answer 1

Erlang VM does not load NIF libraries with publicly accessible global characters - it will permanently pollute the global namespace.

Theoretically, and I do not know if this will always be true, plugins should be able to dynamically load their parent library in order to search for its characters, without forcing the OS to load another library image.