On Sun, Feb 15, 2015 at 1:14 PM, Alexander Monakov <amona...@ispras.ru> wrote:
>
>
> On Sun, 15 Feb 2015, Cyd Haselton wrote:
>
>> On Sun, Feb 15, 2015 at 11:53 AM, Alexander Monakov <amona...@ispras.ru>
>> wrote:
>> >> Given that info...and in spite of my aforementioned limited knowledge I
>> >> went back to take another look at the source and found this in
>> >> libfakechroot.c
>> >>
>> >> /bld/fakechrt/fakechroot-2.16 $ grep -C 4 dlsym src/libfakechroot.c
>> >> /* Lazily load function */
>> >> LOCAL fakechroot_wrapperfn_t fakechroot_loadfunc (struct
>> >> fakechroot_wrapper * w)
>> >> {
>> >> char *msg;
>> >> if (!(w->nextfunc = dlsym(RTLD_NEXT, w->name))) {;
>> >> msg = dlerror();
>> >> fprintf(stderr, "%s: %s: %s\n", PACKAGE, w->name, msg != NULL ?
>> >> msg : "unresolved symbol");
>> >> exit(EXIT_FAILURE);
>> >> }
>> >>
>> >> I'm fairly certain I remember reading something about Android and lazy
>> >> function loading....how it doesn't handle it well or does so differently
>> >> from standard Linux builds. At any rate, I believe the above code is
>> >> responsible for those annoying 'fakechroot: undefined reference to dlopen'
>> >> errors, so I'll see if I can fix that.
>> >
>> > In Android's Bionic libc, the implementation of dlopen() resides in the
>> > dynamic loader, and not present in libdl.so.
>>
>> Yet in Android's NDK documentation, they state that in order to use
>> dlopen() functionality in native code you must link against libdl and
>> include dlfcn.h. Why would this be the case if the dlopen()
>> implementation is not in libdl?
>> (documentation link: http://www.kandroid.org/ndk/docs/STABLE-APIS.html)
>
> That's the standard way of using dlopen, i.e. same as you would do it on Linux
> with glibc for example. So the link merely says that you can get dlopen the
> same way as usual.
>
> The difference is that Android's libdl only contains stub symbols for
> dlopen&co, and the real symbols can be looked up in the dynamic loader. That
> RTLD_NEXT does not work for obtaining a pointer for dlopen, as it works on
> glibc, is quite unfortunate, and probably a bug in Bionic.
>
> Alexander
Would it have anything to do with Android's symbol searching method?
I.e. a library must be explicitly linked and loaded if needed; on load
a library won't look to already loaded libraries to resolve symbols?
