dlib link failure

[takotakot]

I encountered a problem linking to dlib when compiling gazr (https://github.com/severin-lemaignan/gazr). I reported the issue to severin-lemaignan/gazr#21 but maybe it's dlib problem.

Expected Behavior

lib/libdlib.so or lib/libdlib.so.x.y.z is used for link.

Current Behavior

lib/libdlib.a is given.

Steps to Reproduce

# dlib
cmake -DCMAKE_INSTALL_PREFIX:PATH=/home/takotakot/dlib_install/ -DBUILD_SHARED_LIBS=ON ..
make
make install

# gazr
dlib_DIR=/home/takotakot/dlib_install/ cmake .. -DWITH_ROS=false
make

Got error: /usr/bin/ld: /home/takotakot/dlib_install/lib/libdlib.a(base64_kernel_1.cpp.o): relocation R_X86_64_32S against `_ZTVN4dlib6base64E' can not be used when making a shared object; recompile with -fPIC

When I changed the file path from /home/takotakot/dlib_install/lib/libdlib.a to /home/takotakot/dlib_install/lib/libdlib.so manually, I could comiple libgazr.so .

• Version: 23499b7
• Where did you get dlib: github
• Platform: x86_64
• Compiler: Ubuntu 5.4.0-6ubuntu1~16.04.5

[davisking]

If you changed libgazr's target_link_libraries call to link against dlib::dlib_shared it works.

[davisking]

For reference, there is some discussion of this here #923. I still don't think that changing the dlib cmake files to build either a shared or static library based on BUILD_SHARED_LIBS is a good idea. I'm open to arguments against this view, but they need to address all the use cases.

[takotakot]

Thank you very much. I'll try other options for dlib and change libgazr's target and report again.

[davisking]

You could also compile dlib with position independent code by setting CMAKE_POSITION_INDEPENDENT_CODE to true.