Generate a pkgconf pc file from cmake

[harshula]

While adding pkgconf support to an old fork of FMS, built via Spack, I noticed that the upstream FMS' CMake was not generating the pkgconf pc file.

Testing output:

/opt/release/linux-rocky8-x86_64/intel-2021.2.0/fms-test-b6u4j7f37pf4m2sxontqprjm5wklfxlz/lib64/pkgconfig/FMS.pc:

prefix=/opt/release/linux-rocky8-x86_64/intel-2021.2.0/fms-test-b6u4j7f37pf4m2sxontqprjm5wklfxlz
exec_prefix=/opt/release/linux-rocky8-x86_64/intel-2021.2.0/fms-test-b6u4j7f37pf4m2sxontqprjm5wklfxlz
libdir=/opt/release/linux-rocky8-x86_64/intel-2021.2.0/fms-test-b6u4j7f37pf4m2sxontqprjm5wklfxlz/lib64
includedir=/opt/release/linux-rocky8-x86_64/intel-2021.2.0/fms-test-b6u4j7f37pf4m2sxontqprjm5wklfxlz/include

# Including the following, as they may be useful when building other components
# and as a way to better record how the library was built.
ccompiler=/opt/spack/lib/spack/env/intel/icc
fccompiler=/opt/spack/lib/spack/env/intel/ifort
cppflagss.compiled=
cflags.compiled= -sox -traceback
fcflags.compiled= -fpp -fno-alias -auto -safe-cray-ptr -ftz -assume byterecl -align array64byte -nowarn -sox -traceback
ldflags.compiled=

Name: FMS
Description: The Flexible Modeling System Infrastructure Library
URL: https://www.gfdl.noaa.gov/fms
Version: 2024.2.0
Libs: -L${libdir} -lFMS
Libs.private:
Cflags: -I${includedir}
Fflags: -I${includedir}

What are the relevant CMake variables that should go in Libs.private? Also, ${CMAKE_INSTALL_LIBDIR} is lib64 whereas the FMS library is installed in lib.

[rem1776]

What are the relevant CMake variables that should go in Libs.private? Also, ${CMAKE_INSTALL_LIBDIR} is lib64 whereas the FMS library is installed in lib.

@harshula Sorry for the delay, didn't notice that question in there initially. The required flags would be for netcdf and mpi. libyaml is also used optionally. I think the relevant CMake variables would be here:

FMS/cmake/FindNetCDF.cmake

Lines 34 to 36 in 53c55b4

	# - NetCDF_<comp>_LIBRARIES - the libraries for the component
	# - NetCDF_<comp>_LIBRARY_SHARED - Boolean is true if libraries for component are shared
	# - NetCDF_<comp>_INCLUDE_DIRS - the include directories for specified component

FMS/cmake/Findlibyaml.cmake

Lines 3 to 4 in 53c55b4

	# LIBYAML_INCLUDE_DIR
	# LIBYAML_LIBRARIES

I think MPI_C/Fortran_INCLUDE_DIRS and MPI_C/Fortran_LINK_FLAGS would be the ones for MPI, but I'm not 100% sure on that.

@climbfuji Do you know why there would be the difference in the install directory locations? Since we mainly utilize the autotools build I figure you may have more insight than me.

[climbfuji]

What are the relevant CMake variables that should go in Libs.private? Also, ${CMAKE_INSTALL_LIBDIR} is lib64 whereas the FMS library is installed in lib.

@harshula Sorry for the delay, didn't notice that question in there initially. The required flags would be for netcdf and mpi. libyaml is also used optionally. I think the relevant CMake variables would be here:

FMS/cmake/FindNetCDF.cmake

Lines 34 to 36 in 53c55b4

	# - NetCDF_<comp>_LIBRARIES - the libraries for the component
	# - NetCDF_<comp>_LIBRARY_SHARED - Boolean is true if libraries for component are shared
	# - NetCDF_<comp>_INCLUDE_DIRS - the include directories for specified component

FMS/cmake/Findlibyaml.cmake

Lines 3 to 4 in 53c55b4

	# LIBYAML_INCLUDE_DIR
	# LIBYAML_LIBRARIES

I think MPI_C/Fortran_INCLUDE_DIRS and MPI_C/Fortran_LINK_FLAGS would be the ones for MPI, but I'm not 100% sure on that.

@climbfuji Do you know why there would be the difference in the install directory locations? Since we mainly utilize the autotools build I figure you may have more insight than me.

Are you referring to the comment above that libfms goes into lib instead of lib64? As far as I know, you can use GNUInstallDirs https://cmake.org/cmake/help/latest/module/GNUInstallDirs.html in cmake, which sets the install directories correctly for whatever system you are on?

[rem1776]

@climbfuji Yeah that's what I was referring to, thanks for the info.

It seems like this line should be updated to use whichever lib directory is set by GNUInstallDirs.

FMS/CMakeLists.txt

Line 438 in d13c129

set(CONFIG_INSTALL_DESTINATION lib/cmake/fms)

[harshula]

Notes
https://people.freedesktop.org/~dbn/pkg-config-guide.html#writing
https://people.freedesktop.org/~dbn/pkg-config-guide.html#faq

[climbfuji]

@climbfuji Yeah that's what I was referring to, thanks for the info.

It seems like this line should be updated to use whichever lib directory is set by GNUInstallDirs.

FMS/CMakeLists.txt

Line 438 in d13c129

set(CONFIG_INSTALL_DESTINATION lib/cmake/fms)

Is that line needed at all? Shouldn't cmake place those cmake files in the correct place w/o it?

[rem1776]

Is that line needed at all? Shouldn't cmake place those cmake files in the correct place w/o it?

I think it might be needed as a required argument for configure_package_config_file.

[harshula]

Hi @rem1776 & @climbfuji , I've created a separate PR, #1589 , to decide on ${CMAKE_INSTALL_LIBDIR} Vs lib. After that decision is made, I will update this PR accordingly.

[harshula]

Hi @rem1776 & @climbfuji , I did an FMS 2024.03.tar.gz autotools build while using Spack built dependencies. I built netcdf as static libraries, using Spack ( spack install --only dependencies fms %intel@2021.2.0 target=x86_64 ^netcdf-c~shared ^netcdf-fortran~shared).

The FMS.pc file looks like:

#***********************************************************************
#*                   GNU Lesser General Public License
#*
#* This file is part of the GFDL Flexible Modeling System (FMS).
#*
#* FMS is free software: you can redistribute it and/or modify it under
#* the terms of the GNU Lesser General Public License as published by
#* the Free Software Foundation, either version 3 of the License, or (at
#* your option) any later version.
#*
#* FMS is distributed in the hope that it will be useful, but WITHOUT
#* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
#* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
#* for more details.
#*
#* You should have received a copy of the GNU Lesser General Public
#* License along with FMS.  If not, see <http://www.gnu.org/licenses/>.
#***********************************************************************

prefix=/opt
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

# Including the following, as they may be useful when building other components
# and as a way to better record how the library was built.
ccompiler=mpicc
fccompiler=mpifort
cppflagss.compiled= -fopenmp
cflags.compiled=-I/opt/release/linux-rocky8-x86_64/intel-2021.2.0/netcdf-c-4.9.2-chhxlgbmo52jl5jxr6jdduooa5hukdji/include -fopenmp
fcflags.compiled=-I/opt/release/linux-rocky8-x86_64/intel-2021.2.0/netcdf-fortran-4.6.1-o7w4mq2twc22q6k4wq5lu7le36jzfaws/include -I/opt/release/linux-rocky8-x86_64/intel-2021.2.0/netcdf-fortran-4.6.1-o7w4mq2twc22q6k4wq5lu7le36jzfaws/include  -FR -real-size 64 -fopenmp
ldflags.compiled=-L/opt/release/linux-rocky8-x86_64/intel-2021.2.0/netcdf-c-4.9.2-chhxlgbmo52jl5jxr6jdduooa5hukdji/lib -L/opt/release/linux-rocky8-x86_64/intel-2021.2.0/hdf5-1.14.3-hhugjls2qcwfrp5bdscl7s2sxleqsuyw/lib -lnetcdf -lhdf5_hl -lhdf5 -lm -L/opt/release/linux-rocky8-x86_64/intel-2021.2.0/netcdf-fortran-4.6.1-o7w4mq2twc22q6k4wq5lu7le36jzfaws/lib -lnetcdff -lnetcdf -lm -L/opt/release/linux-rocky8-x86_64/intel-2021.2.0/netcdf-c-4.9.2-chhxlgbmo52jl5jxr6jdduooa5hukdji/lib -L/opt/release/linux-rocky8-x86_64/intel-2021.2.0/hdf5-1.14.3-hhugjls2qcwfrp5bdscl7s2sxleqsuyw/lib -lnetcdf -lhdf5_hl -lhdf5 -lm

Name: FMS
Description: The Flexible Modeling System Infrastructure Library
URL: https://www.gfdl.noaa.gov/fms
Version: 2024.03
Libs: -L$(libdir) -lFMS
Libs.private: -lnetcdff -lnetcdf 
Cflags: -I${includedir}
Fflags: -I${includedir}

The above appears to confirm the Guide to pkg-config:

Libs.private: The link flags for private libraries required by this package but not exposed to applications.