Ruby

begin

# BSD

#

# If dlsym() is called with the special handle RTLD_NEXT, then the search

# for the symbol is limited to the shared objects which were loaded after

# the one issuing the call to dlsym(). Thus, if the function is called

# from the main program, all the shared libraries are searched. If it is

# called from a shared library, all subsequent shared libraries are

# searched. RTLD_NEXT is useful for implementing wrappers around library

# functions. For example, a wrapper function getpid() could access the

# "real" getpid() with dlsym(RTLD_NEXT, "getpid"). (Actually, the dlfunc()

# interface, below, should be used, since getpid() is a function and not a

# data object.)

# --- FreeBSD 8.0 dlsym(3)

require 'objspace'

handle = Handle::NEXT

refute_nil handle['Init_objspace']

rescue

# AIX

#

# The behavior of AIX for RTLD_NEXT is the same as that of BSD.

# However, the problem is that on AIX, Ruby's extension libraries do not

# export their symbols, because they are loaded not by dlopen(3)/dlsym(3)

# but by load(3) (See dln.c). This means 'Init_objspace' is not the search

# target of RTLD_NEXT and the test above results in nil.

# Fortunately, on AIX, helper.rb creates and loads a dummy shared library,

# libaixdltest.so, which contains 'strcpy' and some other functions,

# so we can take advantage of it for testing RTLD_NEXT.

handle = Handle::NEXT

refute_nil handle['strcpy']

end