Specifying Exact Library to Link with In Automake

Question

I am having extreme trouble cross compiling a project related to gstreamer. I am trying to link it to a library on my cross compile machine's /usr/lib

If I do the standard linker flags -L{FILESYS_DIR}/usr/lib -lGLESv2 I get pthread complaints from my cross compile toolchain. Thus, I am trying to link to this library without using the -L flag.

No matter what I do, I am getting undefined symbol glFramebuffer2D. However a quick readelf -Wc $FILESYS_DIR/usr/lib/libGLESv2.so | glFrame shows me a glFramebuffer2D symbol.

I'm pulling my hair out because no matter what flags I specify to autoconf, something called libtool throws away my link request unless I use the -L -l approach...

Edit: I had another idea, I tried -Wl, $FILESYS_DIR/usr/lib/libGLESv2.so which worked in compiling and linking but not during runtime... Obvious to me (now) because the host machine root is $FILESYS_DIR. Anyways, this is on the right approach, but I guess I need relative names.

libtool: link:  arm-none-linux-gnueabi-gcc -shared  .libs/libgstbla_la-gstblaoverlay.o
  .libs/libgstbla_la-gstblastabilize.o .libs/libgstbla_la-gles2_utilities.o   -Wl,-
  rpath -Wl,/home/z3/z3-netra/filesys/fs//opt/gstreamer-0.4/lib -Wl,-rpath -
  Wl,/home/z3/z3-netra/filesys/fs//opt/gstreamer-0.4/lib -L/home/z3/z3-
  netra/filesys/fs/opt/gstreamer/lib /home/z3/z3-netra/filesys/fs//opt/gstreamer-
  0.4/lib/libgstbase-0.10.so /home/z3/z3-netra/filesys/fs//opt/gstreamer-
  0.4/lib/libgstreamer-0.10.so /home/z3/z3-netra/filesys/fs//opt/gstreamer-
  0.4/lib/libgstvideo-0.10.so /home/z3/z3-netra/filesys/fs//opt/gstreamer-
  0.4/lib/libgobject-2.0.so /home/z3/z3-netra/filesys/fs//opt/gstreamer-
  0.4/lib/libgmodule-2.0.so /home/z3/z3-netra/filesys/fs//opt/gstreamer-
  0.4/lib/libgthread-2.0.so -lrt /home/z3/z3-netra/filesys/fs//opt/gstreamer-
  0.4/lib/libglib-2.0.so    -pthread -Wl,-soname -Wl,libgstbla.so -Wl,-version-script -
  Wl,.libs/libgstbla.ver -o .libs/libgstbla.so

If needed, in one line as well:

libtool: link:  arm-none-linux-gnueabi-gcc -shared  .libs/libgstbla_la-gstblaoverlay.o .libs/libgstbla_la-gstblastabilize.o .libs/libgstbla_la-gles2_utilities.o   -Wl,-rpath -Wl,/home/z3/z3-netra/filesys/fs//opt/gstreamer-0.4/lib -Wl,-rpath -Wl,/home/z3/z3-netra/filesys/fs//opt/gstreamer-0.4/lib -L/home/z3/z3-netra/filesys/fs/opt/gstreamer/lib /home/z3/z3-netra/filesys/fs//opt/gstreamer-0.4/lib/libgstbase-0.10.so /home/z3/z3-netra/filesys/fs//opt/gstreamer-0.4/lib/libgstreamer-0.10.so /home/z3/z3-netra/filesys/fs//opt/gstreamer-0.4/lib/libgstvideo-0.10.so /home/z3/z3-netra/filesys/fs//opt/gstreamer-0.4/lib/libgobject-2.0.so /home/z3/z3-netra/filesys/fs//opt/gstreamer-0.4/lib/libgmodule-2.0.so /home/z3/z3-netra/filesys/fs//opt/gstreamer-0.4/lib/libgthread-2.0.so -lrt /home/z3/z3-netra/filesys/fs//opt/gstreamer-0.4/lib/libglib-2.0.so    -pthread -Wl,-soname -Wl,libgstbla.so -Wl,-version-script -Wl,.libs/libgstbla.ver -o .libs/libgstbla.so

You use `-Wl,-rpath`, twice, without actually setting a run-time path. Set those to valid library paths on the target system and it should hopefully work better. — Some programmer dude, Sep 05 '12 at 06:05
Interesting, note that is link call is generated for me by Automake. I will look around and see if I can fix that specific issue. — Constantin, Sep 05 '12 at 14:22
When you say "no matter what flags I specify to autoconf", are you referring to flags that you specify to the configure script? — William Pursell, Sep 05 '12 at 16:34
@JoachimPileborg there is a run-time path: it's set in the following -Wl argument: `-Wl,/home/z3/z3-netra/filesys/fs//opt/gstreamer-0.4/lib` — Bernd Jendrissek, Sep 08 '12 at 00:51

score 0 · Answer 1 · answered Sep 08 '12 at 01:07

/usr/lib should already be on the library search path, so you shouldn't need to specify an RPATH. What you do need to do though, is to tell your (cross-)linker where to find the libraries. I think that includes transitively dependencies, such as libpthread. Do you have $FILESYS_DIR/usr/lib/libpthread.so? Does it point to /lib/libpthread.so.N? Oh wait, I see something now that I wrote it out: notice the (likely) absence of $FILESYS_DIR there: so it's possible that your linker is looking for libpthread transitively needed by libGLESv2, but not finding it, since $FILESYS_DIR/lib is not on the library include path. Add -L $FILESYS_DIR/lib to your linker flags and try again.

score 0 · Accepted Answer · edited May 23 '17 at 12:27

All, this was related to the following question: set global gcc default search paths

The problem here is related to the pthread.so (also glib.so). /usr/lib/pthread.so on a lot of systems is an ASCII script which then further links to the system's /lib/pthread.so.0 (which is a soft link). When compiling, my $(FILESYS_DIR) was correct, however the the libpthread.so there pointed to the host systems pthread.so

I made a HUGE mistake here which could have been easily avoided with correct cross compilation management. When compiling for a target system, do not use files on the target system filesystem (if it's a NFS as mine was.) Use local libraries compiled for that target system. FURTHERMORE, specify -Wl,-rpath-link=/[local location where your *.so reside]

That compiler/linker flag allows for the runtime path to be on the local system during compile and link, but maintain the standard runtime path during runtime.... Hope that made sense.

Specifying Exact Library to Link with In Automake

2 Answers2