Can't seem to set up a top level CMakeLists.txt for the entire code gallery

[bangerth]

This might need @tamiko 's input:

I've gotten tired of configuring and compiling each code gallery program individually, so I tried to set up this CMakeLists.txt file in the top level of the code gallery:

cmake_minimum_required(VERSION 3.13.4)
project(code-gallery)

add_subdirectory(advection_reaction_estimator)

Interestingly, this does not work. When I create a build directory and call cmake .. from there, the output is the following:

-- The CXX compiler identification is GNU 4.8.5
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - failed
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ - broken
CMake Error at /raid/bangerth/bin/share/cmake-3.20/Modules/CMakeTestCXXCompiler.cmake:59 (message):
  The C++ compiler

    "/usr/bin/c++"

  is not able to compile a simple test program.

  It fails with the following output:

    Change Dir: /home/fac/g/bangerth/p/deal.II/1/code-gallery/build/CMakeFiles/CMakeTmp

    Run Build Command(s):/usr/bin/gmake -f Makefile cmTC_f0d54/fast && /usr/bin/gmake  -f CMakeFiles/cmTC_f0d54.dir/build.make CMakeFiles/cmTC_f0d54.dir/build
    gmake[1]: Entering directory `/raid/bangerth/p/deal.II/1/code-gallery/build/CMakeFiles/CMakeTmp'
    gmake[1]: Warning: File `CMakeFiles/cmTC_f0d54.dir/progress.make' has modification time 0.0017 s in the future
    Building CXX object CMakeFiles/cmTC_f0d54.dir/testCXXCompiler.cxx.o
    /usr/bin/c++   -std=c++20  -o CMakeFiles/cmTC_f0d54.dir/testCXXCompiler.cxx.o -c /home/fac/g/bangerth/p/deal.II/1/code-gallery/build/CMakeFiles/CMakeTmp/testCXXCompiler.cxx
    c++: error: unrecognized command line option ‘-std=c++20’
    gmake[1]: *** [CMakeFiles/cmTC_f0d54.dir/testCXXCompiler.cxx.o] Error 1
    gmake[1]: Leaving directory `/raid/bangerth/p/deal.II/1/code-gallery/build/CMakeFiles/CMakeTmp'
    gmake: *** [cmTC_f0d54/fast] Error 2

  CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
  CMakeLists.txt:8 (project)

-- Configuring incomplete, errors occurred!

That is, it errors out while trying to identify a C++ compiler, which it takes from /usr/bin, but this is not the one I want it to use nor the one it should find via my $PATH:

 which c++
/scratch/local/gcc-11.2.0/bin/c++

It is also not the one it should inherit from the deal.II configuration system. (The specific error you see above is because I do `export CXXFLAGS=-std=c++20 which the system compiler predictably does not understand, it being GCC 4.8.)

Curiously, if I call cmake from the subdirectory into which I asked cmake to recurse (namely, advection_reaction_estimator), then this all works:

code-gallery/build> cd ../advection_reaction_estimator/
reaction_estimator> cmake .
-- The CXX compiler identification is GNU 11.2.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /scratch/local/gcc-11.2.0/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Using the deal.II-9.5.0-pre installation found at /home/fac/g/bangerth/p/deal.II/1/install
-- Include macro /home/fac/g/bangerth/p/deal.II/1/install/share/deal.II/macros/macro_deal_ii_add_test.cmake
-- Include macro /home/fac/g/bangerth/p/deal.II/1/install/share/deal.II/macros/macro_deal_ii_initialize_cached_variables.cmake
-- Include macro /home/fac/g/bangerth/p/deal.II/1/install/share/deal.II/macros/macro_deal_ii_invoke_autopilot.cmake
-- Include macro /home/fac/g/bangerth/p/deal.II/1/install/share/deal.II/macros/macro_deal_ii_pickup_tests.cmake
-- Include macro /home/fac/g/bangerth/p/deal.II/1/install/share/deal.II/macros/macro_deal_ii_query_git_information.cmake
-- Include macro /home/fac/g/bangerth/p/deal.II/1/install/share/deal.II/macros/macro_deal_ii_setup_target.cmake
-- Include macro /home/fac/g/bangerth/p/deal.II/1/install/share/deal.II/macros/macro_shell_escape_option_groups.cmake
-- Include macro /home/fac/g/bangerth/p/deal.II/1/install/share/deal.II/macros/macro_target_compile_flags.cmake
-- Include macro /home/fac/g/bangerth/p/deal.II/1/install/share/deal.II/macros/macro_target_link_flags.cmake
###
#
#  WARNING:
#
#  CMAKE_BUILD_TYPE "" unsupported by current installation!
#  deal.II was configured with "DebugRelease".
#
#  CMAKE_BUILD_TYPE was forced to "Debug".
#
###
-- The C compiler identification is GNU 11.2.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /scratch/local/gcc-11.2.0/bin/gcc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Autopilot invoked
###
#
#  Project  DG_advection_reaction_estimator  set up with  deal.II-9.5.0-pre  found at
#      /home/fac/g/bangerth/p/deal.II/1/install
#
#  CMAKE_BUILD_TYPE:          Debug
#
#  You can now run
#       $ make                - to compile and link the program
#       $ make run            - to (compile, link and) run the program
#
#       $ make debug          - to switch the build type to 'Debug'
#       $ make release        - to switch the build type to 'Release'
#
#       $ make edit_cache     - to change (cached) configuration variables
#                               and rerun the configure and generate phases of CMake
#
#       $ make strip_comments - to strip the source files in this
#                               directory off their comments; this is irreversible
#       $ make clean          - to remove the generated executable as well as
#                               all intermediate compilation files
#       $ make runclean       - to remove all output generated by the program
#       $ make distclean      - to clean the directory from _all_ generated
#                               files (includes clean, runclean and the removal
#                               of the generated build system)
#       $ make info           - to view this message again
#
#  Have a nice day!
#
###
-- Configuring done
-- Generating done
-- Build files have been written to: /home/fac/g/bangerth/p/deal.II/1/code-gallery/advection_reaction_estimator

How do we make this work? Or is setting up multiple deal.II-based projects at once just not supported?

[masterleinad]

I wouldn't expect in a CMake project that the compiler is inferred from any of the dependencies and specifying the compiler explicitly should still work. I am getting

$ cmake -DCMAKE_CXX_COMPILER=clang++ -DDEAL_II_DIR=~/Software/dealii-install/ ..
-- The C compiler identification is AppleClang 14.0.0.14000029
-- The CXX compiler identification is Clang 15.0.7
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /Library/Developer/CommandLineTools/usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /opt/homebrew/Cellar/llvm/15.0.7_1/bin/clang++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Using the deal.II-9.5.0-pre installation found at /Users/darndt/Software/dealii-install
-- Include macro /Users/darndt/Software/dealii-install/share/deal.II/macros/macro_deal_ii_add_test.cmake
-- Include macro /Users/darndt/Software/dealii-install/share/deal.II/macros/macro_deal_ii_initialize_cached_variables.cmake
-- Include macro /Users/darndt/Software/dealii-install/share/deal.II/macros/macro_deal_ii_invoke_autopilot.cmake
-- Include macro /Users/darndt/Software/dealii-install/share/deal.II/macros/macro_deal_ii_pickup_tests.cmake
-- Include macro /Users/darndt/Software/dealii-install/share/deal.II/macros/macro_deal_ii_query_git_information.cmake
-- Include macro /Users/darndt/Software/dealii-install/share/deal.II/macros/macro_deal_ii_setup_target.cmake
-- Include macro /Users/darndt/Software/dealii-install/share/deal.II/macros/macro_shell_escape_option_groups.cmake
-- Include macro /Users/darndt/Software/dealii-install/share/deal.II/macros/macro_target_compile_flags.cmake
-- Include macro /Users/darndt/Software/dealii-install/share/deal.II/macros/macro_target_link_flags.cmake
###
#
#  WARNING:
#
#  CMAKE_BUILD_TYPE "" unsupported by current installation!
#  deal.II was configured with "DebugRelease".
#
#  CMAKE_BUILD_TYPE was forced to "Debug".
#
###
-- Autopilot invoked
###
#
#  Project  DG_advection_reaction_estimator  set up with  deal.II-9.5.0-pre  found at
#      /Users/darndt/Software/dealii-install
#
#  CMAKE_BUILD_TYPE:          Debug
#
#  You can now run
#       $ make                - to compile and link the program
#       $ make run            - to (compile, link and) run the program
#
#       $ make sign           - to sign the executable with the supplied OSX developer key
#
#       $ make debug          - to switch the build type to 'Debug'
#       $ make release        - to switch the build type to 'Release'
#
#       $ make edit_cache     - to change (cached) configuration variables
#                               and rerun the configure and generate phases of CMake
#
#       $ make strip_comments - to strip the source files in this
#                               directory off their comments; this is irreversible
#       $ make clean          - to remove the generated executable as well as
#                               all intermediate compilation files
#       $ make runclean       - to remove all output generated by the program
#       $ make distclean      - to clean the directory from _all_ generated
#                               files (includes clean, runclean and the removal
#                               of the generated build system)
#       $ make info           - to view this message again
#
#  Have a nice day!
#
###
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/darndt/Software/dealii-code-gallery/build

[bangerth]

Ah, interesting. Using -DCMAKE_CXX_COMPILER actually works -- though it's not clear to me because I don't have to do that when configuring the individual code gallery programs, nor when configuring deal.II. It just gets the compiler from $PATH.

Anyway, the next problem we run into is then this:

CMake Error at /home/fac/g/bangerth/p/deal.II/1/install/share/deal.II/macros/macro_deal_ii_invoke_autopilot.cmake:89 (add_custom_target):
  add_custom_target cannot create target "run" because another target with
  the same name already exists.  The existing target is a custom target
  created in source directory
  "/home/fac/g/bangerth/p/deal.II/1/code-gallery/advection_reaction_estimator".
  See documentation for policy CMP0002 for more details.
Call Stack (most recent call first):
  NavierStokes_TRBDF2_DG/CMakeLists.txt:54 (DEAL_II_INVOKE_AUTOPILOT)

and many more of the same kind.

[masterleinad]

Right. This would work better if we were to use a more CMake-native approach again. 🙂 Something like

diff --git a/advection_reaction_estimator/CMakeLists.txt b/advection_reaction_estimator/CMakeLists.txt
index 826f55b..3091738 100644
--- a/advection_reaction_estimator/CMakeLists.txt
+++ b/advection_reaction_estimator/CMakeLists.txt
@@ -23,6 +23,5 @@ IF(NOT ${deal.II_FOUND})
     )
 ENDIF()

-DEAL_II_INITIALIZE_CACHED_VARIABLES()
-PROJECT(${TARGET})
-DEAL_II_INVOKE_AUTOPILOT()
+ADD_EXECUTABLE(${TARGET} ${TARGET_SRC})
+TARGET_LINK_LIBRARIES(${TARGET} dealii::dealii)

[bangerth]

Yes. Once @tamiko has this all in a stable state, that's what we may want to do with the tutorials first, and then also the code gallery...