get_target_property of INCLUDE_DIRECTORIES on CGAL::CGAL is not set

[VincentRouvreau]

Issue Details

It would be nice if get_target_property(CGAL_TARGET_INCLUDE_DIRECTORIES CGAL::CGAL INCLUDE_DIRECTORIES) was returning the CGAL include directory.

Source Code

Here is a CMake file to reproduce the behaviour:

cmake_minimum_required(VERSION 3.8)
project(minimal_cgal_dependency)

find_package(CGAL QUIET)

get_target_property(CGAL_TARGET_INTERFACE_INCLUDE_DIRECTORIES CGAL::CGAL INTERFACE_INCLUDE_DIRECTORIES)
message("*** CGAL_TARGET_INTERFACE_INCLUDE_DIRECTORIES = ${CGAL_TARGET_INTERFACE_INCLUDE_DIRECTORIES}")
# This seems OK, but not convenient
# *** CGAL_TARGET_INTERFACE_INCLUDE_DIRECTORIES = /miniconda3/envs/custom-cgal/include;/miniconda3/envs/custom-cgal/include;/miniconda3/envs/custom-cgal/include;$<BUILD_INTERFACE:/workspace/contrib/CGAL-5.5.3/include>;$<INSTALL_INTERFACE:include>

get_target_property(CGAL_TARGET_INCLUDE_DIRECTORIES CGAL::CGAL INCLUDE_DIRECTORIES)
message("*** CGAL_TARGET_INCLUDE_DIRECTORIES = ${CGAL_TARGET_INCLUDE_DIRECTORIES}")
# This behaviour would be convenient
# *** CGAL_TARGET_INCLUDE_DIRECTORIES = CGAL_TARGET_INCLUDE_DIRECTORIES-NOTFOUND

message("*** CGAL_INCLUDE_DIRS = ${CGAL_INCLUDE_DIRS}")
# The 'old' behaviour is still ok
# *** CGAL_INCLUDE_DIRS = /workspace/contrib/CGAL-5.5.3/include

...

Environment

• Operating system (Windows/Mac/Linux, 32/64 bits): Linux 64 bits
• Compiler: g++ (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
• Release or debug mode: Release mode
• Specific flags used (if any):
• CGAL version: Same behaviour with CGAL 5.1.5, 5.5.3 and 6.0-I-207 (master from some days ago)
• Boost version: 1.84.0
• Other libraries versions if used (Eigen, TBB, etc.):
  cmake 3.29.0 hcfe8598_0 conda-forge
  eigen 3.4.0 h00ab1b0_0 conda-forge
  gmp 6.3.0 h59595ed_1 conda-forge
  mpfr 4.2.1 h9458935_0 conda-forge

[lrineau]

I do not get it. Target properties like INCLUDE_DIRECTORIES or INTERFACE_INCLUDE_DIRECTORIES are not meant to be consumed by users of the target. They are set by CMake.

CGAL::CGAL should actually have INTERFACE_INCLUDE_DIRECTORIES empty, in favor of INTERFACE_SYSTEM_INCLUDE_DIRECTORIES.

${CGAL_INCLUDE_DIRS} is the contract we have with CGAL users, and should stay stable over versions of CGAL. Why does it not fit your needs? What are you trying to do?

[VincentRouvreau]

Sorry if I am out of topic, I am far to be a CMake expert...
But if I read this stackoverflow, it seems to be the modern way to get include/lib directory for a target.

And yes, for sure, you can keep ${CGAL_INCLUDE_DIRS} for backward compatibility, I do not have any issue with this (and I will keep using it).

[lrineau]

In modern CMake, you usually link with imported targets like CGAL::CGAL, and do not deal with include dirs, libraries, definitions, compiler options...

Vincent, if you explain why you need the include directory of CGAL, I might help you with that.

[VincentRouvreau]

Yes, for sure. As you may know, gudhi is using some nice cgal features. So for the c++ part, it is quite easy with cmake:

...
find_package(Boost REQUIRED)
find_package(CGAL)

if (CGAL_FOUND)
  add_executable ( some_gudhi_program some_gudhi_program.cpp )
  target_link_libraries(some_gudhi_program  CGAL::CGAL)
endif()

(I tried also scikit-build which seems a good and modern candidate, but I was having issues regarding third parties installation with msvc)
But when we do the python bindings, we need to construct a setup.py file with all the user setup. To do so (maybe not the best idea, but this is the design we have chosen), we ask cmake to build this setup.py file.

This is why we need cmake to know from CGAL installation if it is a header only version or if we have to link with some dynamic libraries (here we need its path too), and where are the CGAL header files. This gives us a setup.py file that looks like (simplified version):

from setuptools import setup, Extension, find_packages
from Cython.Build import cythonize

cython_modules = ['simplex_tree', 'alpha_complex', ]

source_dir='/workspace/gudhi/gudhi-devel/src/python/gudhi/'
extra_compile_args=['-DBOOST_RESULT_OF_USE_DECLTYPE', '-DBOOST_ALL_NO_LIB', '-DBOOST_SYSTEM_NO_DEPRECATED', '-std=c++17', '-frounding-math', '-DCGAL_EIGEN3_ENABLED', '-DCGAL_HEADER_ONLY', '-DCGAL_USE_GMP', '-DCGAL_USE_GMPXX', '-DCGAL_USE_MPFR', '-DGUDHI_USE_TBB', ]
extra_link_args=['-s', ]
libraries=['gmp', 'gmpxx', 'mpfr', 'tbb', 'tbbmalloc', ]
library_dirs=['/miniconda3/envs/gudhi-devel/lib', ]
include_dirs = ['/workspace/contrib/CGAL-5.1.5/include', '/miniconda3/envs/gudhi-devel/include', '/workspace/gudhi/gudhi-devel/src/python/gudhi/', '/workspace/gudhi/gudhi-devel/src/Alpha_complex/include', '/workspace/gudhi/gudhi-devel/src/Simplex_tree/include', ]
runtime_library_dirs=['/miniconda3/envs/gudhi-devel/lib', ]

# Create ext_modules list from module list
ext_modules = []
for module in cython_modules:
    ext_modules.append(Extension(
        'gudhi.' + module,
        sources = [source_dir + module + '.pyx',],
        language = 'c++',
        extra_compile_args=extra_compile_args,
        extra_link_args=extra_link_args,
        libraries=libraries,
        library_dirs=library_dirs,
        include_dirs=include_dirs,
        runtime_library_dirs=runtime_library_dirs,))

ext_modules = cythonize(ext_modules, compiler_directives={'language_level': '3'})

setup(
    name = 'gudhi',
    packages=find_packages(),
    author='GUDHI Editorial Board <https://gudhi.inria.fr/contact/>',
    version='3.10.0a1',
    ext_modules = ext_modules,
    python_requires='>=3.5.0',
    install_requires = ['numpy >= 1.15.0',],
    package_data={"": ["*.dll"], },
)

[VincentRouvreau]

Just a reminder that my initial question was to know if it is "normal" that the target property INCLUDE_DIRECTORIES of CGAL::CGAL was not set 😅

[VincentRouvreau]

CGAL::CGAL should actually have INTERFACE_INCLUDE_DIRECTORIES empty, in favor of INTERFACE_SYSTEM_INCLUDE_DIRECTORIES.

🤔 Interesting ! Maybe I was not asking for the correct target property... Here is what I have for CGAL in comparison with TBB and Eigen3, for instance:

get_target_property(EIGEN3_INTERFACE_SYSTEM_INCLUDE_DIRECTORIES Eigen3::Eigen INTERFACE_SYSTEM_INCLUDE_DIRECTORIES)
# EIGEN3_INTERFACE_SYSTEM_INCLUDE_DIRECTORIES=EIGEN3_INTERFACE_SYSTEM_INCLUDE_DIRECTORIES-NOTFOUND
get_target_property(EIGEN3_INTERFACE_INCLUDE_DIRECTORIES Eigen3::Eigen INTERFACE_INCLUDE_DIRECTORIES)
# EIGEN3_INTERFACE_INCLUDE_DIRECTORIES=/miniconda3/envs/custom-cgal/include/eigen3

get_target_property(TBB_INTERFACE_SYSTEM_INCLUDE_DIRECTORIES TBB::tbb INTERFACE_SYSTEM_INCLUDE_DIRECTORIES)
# TBB_INTERFACE_SYSTEM_INCLUDE_DIRECTORIES=TBB_INTERFACE_SYSTEM_INCLUDE_DIRECTORIES-NOTFOUND
get_target_property(TBB_INTERFACE_INCLUDE_DIRECTORIES TBB::tbb INTERFACE_INCLUDE_DIRECTORIES)
# TBB_INTERFACE_INCLUDE_DIRECTORIES=/miniconda3/envs/custom-cgal/include

get_target_property(CGAL_INTERFACE_SYSTEM_INCLUDE_DIRECTORIES CGAL::CGAL INTERFACE_SYSTEM_INCLUDE_DIRECTORIES)
# CGAL_INTERFACE_SYSTEM_INCLUDE_DIRECTORIES=/miniconda3/envs/custom-cgal/include/;/miniconda3/envs/custom-cgal/include/;/miniconda3/envs/custom-cgal/include
get_target_property(CGAL_INTERFACE_INCLUDE_DIRECTORIES CGAL::CGAL INTERFACE_INCLUDE_DIRECTORIES)
# CGAL_INTERFACE_INCLUDE_DIRECTORIES=$<BUILD_INTERFACE:/workspace/contrib/CGAL-6.0-I-207/include>$<INSTALL_INTERFACE:include>/miniconda3/envs/custom-cgal/include;/miniconda3/envs/custom-cgal/include;/miniconda3/envs/custom-cgal/include