The documentation says:
o If the environment variable LD_LIBRARY_PATH is
defined to contain a colon-separated list of direc‐
tories, then these are searched. (As a security
measure this variable is ignored for set-user-ID
and set-group-ID programs.)
However, this is not (completely) the case, as demonstrable by:
Tuesday, 2008-Oct-21 at 16:50:55 - mbt@zest - Linux v2.6.27
Ubuntu Intrepid:[1-59/7133-0]:dl-test> ./dlc dl1.so
LD_LIBRARY_PATH=(null)
LD_LIBRARY_PATH=.
dlc: dl-caller.c:46: main: Assertion `module != ((void *)0)' failed.
zsh: abort (core dumped) ./dlc dl1.so
Tuesday, 2008-Oct-21 at 16:50:57 - mbt@zest - Linux v2.6.27
Ubuntu Intrepid:[1-60/7134-134]:dl-test> LD_LIBRARY_PATH=. ./dlc dl1.so
LD_LIBRARY_PATH=.
LD_LIBRARY_PATH=.
entrypoint_1() has been called.
entrypoint_2() has been called.
1
It would appear that dlopen(3) only considers LD_LIBRARY_PATH at the
time the executable was run, not after the executable alters its own
environment. Either that, or it uses the LD_LIBRARY_PATH from the
process' parent, not its own environment. Not sure which, but the
documentation should probably be updated to reflect this fact. The way
it is written now would indicate that you could modify LD_LIBRARY_PATH
from within the program and load libraries in different locations. I
suspect this is done for reasons of security, but it'd still be good to
be documented.
Thanks,
Mike
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