Static linking using Cmake

[amitibo]

Hi,

I am trying to (cmake) compile a binding to a library that uses a another library (dlib). This library is compiled for static linking. Is it possible to set pybind11 to use static linking?

Thanks,
Amit

[wjakob]

Python extension modules have to be dynamic. However, you can have a dynamic pybind11 module that links to a static library.

Best,
Wenzel

On Oct 26, 2016, at 3:04 PM, Amit Aides notifications@github.com wrote:

Hi,

I am trying to (cmake) compile a binding to a library that uses a another library (dlib). This library is compiled for static linking. Is it possible to set pybind11 to use static linking?

Thanks,
Amit

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[amitibo]

I am linking using CMake, following the docs example:

ADD_SUBDIRECTORY(pybind11)
PYBIND11_ADD_MODULE(pyface pyface.cpp dummy.cpp)
TARGET_LINK_LIBRARIES(pyface dlib ${OpenCV_LIBS})

When running make, I get the following error:

Linking CXX shared module pyface.so
/usr/bin/ld: dlib_build/libdlib.a(threads_kernel_shared.o): relocation R_X86_64_32 against `_ZN4dlib21threads_kernel_shared14thread_starterEPv' can not be used when making a shared object; recompile with -fPIC
dlib_build/libdlib.a: could not read symbols: Bad value

If I understand correctly, it tries to do dynamic linking with the dlib library which is compiled for static linking. How can I request static linking with the dlib library when creating the pyface module?

Thanks,
Amit

[dean0x7d]

Add the following line to enable -fPIC for your dependency:

set_target_properties(dlib PROPERTIES POSITION_INDEPENDENT_CODE TRUE)

Note that this really isn't specific to pybind11. It's general build system and linking for any dynamic library.

[surabhi96]

How to link pybind11 module that links to a static library? I tried TARGET_LINK_LIBRARIES but I seem to be using it wrongly.
Thanks!

[Sberm]

Add the following line to enable -fPIC for your dependency:

set_target_properties(dlib PROPERTIES POSITION_INDEPENDENT_CODE TRUE)

Note that this really isn't specific to pybind11. It's general build system and linking for any dynamic library.

Thank you so much sir