Introduce cmake option to disable Fortran API

.github/workflows/ci.yml

@@ -140,7 +140,17 @@ jobs:
           cmake .. -DCMAKE_INSTALL_PREFIX=../install \
                    -DCMAKE_BUILD_TYPE=Release \
                    -DT8CODE_ROOT=$PWD/../t8code-local/prefix \
-                   -DENABLE_TESTING=ON -DJULIA_PROJECT_PATH=../libtrixi-julia
+                   -DLIBTRIXI_ENABLE_TESTING=ON -DJULIA_PROJECT_PATH=../libtrixi-julia
+
+      - name: Configure without Fortran (test_type == 'regular')
+        if: ${{ matrix.test_type == 'regular' }}
+        run: |
+          mkdir build-nofortran
+          cd build-nofortran
+          cmake .. -DCMAKE_INSTALL_PREFIX=../install-nofortran \
+                   -DCMAKE_BUILD_TYPE=Release \
+                   -DT8CODE_ROOT=$PWD/../t8code-local/prefix \
+                   -DLIBTRIXI_BUILD_FORTRAN_API=OFF
 
       - name: Configure (test_type == 'coverage')
         if: ${{ matrix.test_type == 'coverage' }}
@@ -154,14 +164,20 @@ jobs:
                    -DCMAKE_Fortran_FLAGS="-cpp --coverage -O0" \
                    -DCMAKE_EXE_LINKER_FLAGS="--coverage" \
                    -DCMAKE_SHARED_LINKER_FLAGS="--coverage" \
-                   -DENABLE_TESTING=ON -DJULIA_PROJECT_PATH=../libtrixi-julia
+                   -DLIBTRIXI_ENABLE_TESTING=ON -DJULIA_PROJECT_PATH=../libtrixi-julia
 
       - name: Build
         if: ${{ matrix.test_type == 'regular' || matrix.test_type == 'coverage' || matrix.test_type == 'smoke' }}
         run: |
           cd build
           make -j 2
 
+      - name: Build without Fortran
+        if: ${{ matrix.test_type == 'regular' }}
+        run: |
+          cd build-nofortran
+          make -j 2
+
       - name: Install
         if: ${{ matrix.test_type == 'regular' || matrix.test_type == 'coverage' || matrix.test_type == 'smoke' }}
         run: |
@@ -227,7 +243,7 @@ jobs:
           cmake .. -DCMAKE_INSTALL_PREFIX=../install \
                    -DCMAKE_BUILD_TYPE=Debug \
                    -DT8CODE_ROOT=$PWD/../t8code-local/prefix \
-                   -DUSE_PACKAGE_COMPILER=ON \
+                   -DLIBTRIXI_USE_PACKAGE_COMPILER=ON \
                    -DJULIA_PROJECT_PATH=$PWD/../libtrixi-julia
 
       - name: Build (test_type == 'package-compiler')
@@ -300,6 +316,16 @@ jobs:
         env:
           LIBTRIXI_DEBUG: all
 
+      - name: Run C example (Fortran API disabled)
+        if: ${{ matrix.test_type == 'regular'}}
+        run: |
+          cd build-nofortran/examples
+          mpirun -n 2 trixi_controller_simple_c \
+              ../../libtrixi-julia \
+              ../../LibTrixi.jl/examples/libelixir_p4est2d_euler_sedov.jl
+        env:
+          LIBTRIXI_DEBUG: all
+
       - name: Check error handling of examples
         if: ${{ matrix.test_type == 'regular' || matrix.test_type == 'coverage' }}
         run: |

CMakeLists.txt

@@ -1,7 +1,8 @@
 # Specify the minimum version
 #   3.9  required for regex submatches
 #   3.12 required for policy CMP0074 (using *_ROOT variables)
-cmake_minimum_required ( VERSION 3.12 )
+#   3.13 required for policy CMP0076 (target_sources() command converts relative paths to absolute)
+cmake_minimum_required ( VERSION 3.13 )
 
 # Reconfigure if Project.toml has changed
 set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS "${CMAKE_SOURCE_DIR}/LibTrixi.jl/Project.toml")
@@ -23,8 +24,18 @@ file(WRITE "${CMAKE_BINARY_DIR}/LIBTRIXI_VERSION" "${LIBTRIXI_VERSION}\n")
 project ( trixi VERSION ${LIBTRIXI_VERSION_MAJOR}.${LIBTRIXI_VERSION_MINOR}.${LIBTRIXI_VERSION_PATCH}
           DESCRIPTION "Interface library for using Trixi.jl from C/C++/Fortran" )
 
-# Enable C and Fortran
-enable_language(C Fortran)
+# Additional configuration options
+option( LIBTRIXI_BUILD_FORTRAN_API "Enable the build of the Fortran interface" ON )
+option( LIBTRIXI_ENABLE_TESTING "Build tests using Google Test (C) and test-drive (Fortran)" OFF )
+option( LIBTRIXI_USE_PACKAGE_COMPILER "Build standalone libtrixi.so using PackageCompiler.jl" )
+
+# Enable C always
+enable_language( C )
+
+# Optionally enable Fortran
+if( LIBTRIXI_BUILD_FORTRAN_API )
+    enable_language( Fortran )
+endif()
 
 # Enabling setting rpath for installation
 SET(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
@@ -47,8 +58,7 @@ endif()
 find_package( MPI REQUIRED )
 
 # Find Google Test and test-drive on demand
-option( ENABLE_TESTING "Build tests using Google Test (C) and test-drive (Fortran)" )
-if( ENABLE_TESTING )
+if( LIBTRIXI_ENABLE_TESTING )
     if ( NOT DEFINED JULIA_PROJECT_PATH )
         message( FATAL_ERROR "JULIA_PROJECT_PATH not set, tests will not work.")
     endif()
@@ -57,22 +67,23 @@ if( ENABLE_TESTING )
 
     find_package( GTest REQUIRED )
 
-    set ( TEST_DRIVE_FIND_METHOD fetch )
-    # Option TEST_DRIVE_BUILD_TESTING is hard-coded to ON, could be spared
-    find_package( test-drive REQUIRED )
+    if( LIBTRIXI_BUILD_FORTRAN_API )
+        set ( TEST_DRIVE_FIND_METHOD fetch )
+        # Option TEST_DRIVE_BUILD_TESTING is hard-coded to ON, could be spared
+        find_package( test-drive REQUIRED )
+    endif()
 endif()
 
-# Optionally use PackageCompiler.jl to build standalone libtrixi.so
-option( USE_PACKAGE_COMPILER "Build standalone libtrixi.so using PackageCompiler.jl" )
-
-# Fortran mod file location
-set(CMAKE_Fortran_MODULE_DIRECTORY ${CMAKE_BINARY_DIR})
+if( LIBTRIXI_BUILD_FORTRAN_API )
+    # Fortran mod file location
+    set(CMAKE_Fortran_MODULE_DIRECTORY ${CMAKE_BINARY_DIR})
+endif()
 
-if( USE_PACKAGE_COMPILER )
+if( LIBTRIXI_USE_PACKAGE_COMPILER )
     if ( NOT DEFINED JULIA_PROJECT_PATH )
         message( FATAL_ERROR "JULIA_PROJECT_PATH needs to be set for PackageCompiler.jl.")
     endif()
-    if ( ENABLE_TESTING )
+    if ( LIBTRIXI_ENABLE_TESTING )
         message( NOTICE "Testing is not supported when PackageCompiler is used.")
     endif()
 
@@ -89,10 +100,12 @@ if( USE_PACKAGE_COMPILER )
                         COMMAND ${CMAKE_COMMAND} -E copy ${PC_INIT_SOURCE} ${PC_INIT_BUILD}
                         DEPENDS ${PC_INIT_SOURCE} )
 
-    # Add a library target (libtrixi), only for Fortran module
-    add_library( ${PROJECT_NAME} OBJECT
-        src/api.f90
-    )
+    if( LIBTRIXI_BUILD_FORTRAN_API )
+        # Add a library target (libtrixi), only for Fortran module
+        add_library( ${PROJECT_NAME} OBJECT
+            src/api.f90
+        )
+    endif()
 
     # Custom command to run PackageCompiler.jl to produce libtrixi.so
     add_custom_command( OUTPUT ${PC_LIBTRIXI_SO}
@@ -123,12 +136,18 @@ else()
     # Library target
     add_library ( ${PROJECT_NAME} SHARED
         src/api.c
-        src/api.f90
         src/auxiliary.h
         src/auxiliary.c
         src/trixi.h
     )
 
+    # Build Fortran library target on demand
+    if( LIBTRIXI_BUILD_FORTRAN_API )
+        target_sources (${PROJECT_NAME} PRIVATE
+            src/api.f90
+        )
+    endif()
+
     # Include directories, private
     target_include_directories ( ${PROJECT_NAME} PRIVATE src )
 
@@ -141,7 +160,10 @@ else()
 
 
     # Include directories
-    target_include_directories( ${PROJECT_NAME} PRIVATE src ${JULIA_INCLUDE_DIRS} )
+    # PRIVATE: Do not include internal directory in projects building against libtrixi
+    # SYSTEM: Disable warnings/error from upstream libraries
+    target_include_directories( ${PROJECT_NAME} PRIVATE src )
+    target_include_directories( ${PROJECT_NAME} SYSTEM PRIVATE ${JULIA_INCLUDE_DIRS} )
 
     # Libraries to link
     target_link_libraries( ${PROJECT_NAME} PRIVATE ${JULIA_LIBRARY} )
@@ -160,13 +182,15 @@ else()
     add_library ( ${PROJECT_NAME}_tls OBJECT
         src/tls.c
     )
-    target_include_directories( ${PROJECT_NAME}_tls PRIVATE ${JULIA_INCLUDE_DIRS} )
+    target_include_directories( ${PROJECT_NAME}_tls SYSTEM PRIVATE ${JULIA_INCLUDE_DIRS} )
 
     # Add test on demand
-    if( ENABLE_TESTING )
+    if( LIBTRIXI_ENABLE_TESTING )
         enable_testing()
         add_subdirectory( test/c )
-        add_subdirectory( test/fortran )
+        if( LIBTRIXI_BUILD_FORTRAN_API )
+            add_subdirectory( test/fortran )
+        endif()
     endif()
 
 
@@ -183,7 +207,9 @@ set_target_properties ( ${PROJECT_NAME} PROPERTIES PUBLIC_HEADER src/trixi.h )
 # Common install configuration
 install( TARGETS ${PROJECT_NAME} )
 install( DIRECTORY LibTrixi.jl DESTINATION share/libtrixi PATTERN "lib" EXCLUDE )
-install( FILES ${CMAKE_Fortran_MODULE_DIRECTORY}/libtrixi.mod TYPE INCLUDE)
+if( LIBTRIXI_BUILD_FORTRAN_API )
+    install( FILES ${CMAKE_Fortran_MODULE_DIRECTORY}/libtrixi.mod TYPE INCLUDE)
+endif()
 install( PROGRAMS utils/libtrixi-init-julia TYPE BIN )
 
 # Add examples

README.md

@@ -56,6 +56,8 @@ For building, `cmake` and its typical workflow is used.
     - Specifying the directory `install_directory` for later installation is optional.
     - Optional specification of build type sets some default compiler options for optimized
       or debug code.
+    - By default the Fortran-Interface is built; it may be excluded with
+      `-DLIBTRIXI_BUILD_FORTRAN_API=OFF`.
     - Building with t8code support is optional. It requires to pass
       `-DT8CODE_ROOT=<t8code_install_directory>`.
 
@@ -302,7 +304,7 @@ To try this out, perform the following steps:
     *using cmake*
     - Add
       ```
-      -DUSE_PACKAGE_COMPILER=ON -DJULIA_PROJECT_PATH=<libtrixi-julia_directory>
+      -DLIBTRIXI_USE_PACKAGE_COMPILER=ON -DJULIA_PROJECT_PATH=<libtrixi-julia_directory>
       ```
       to your cmake call (see above)
 3. From inside the `examples` folder you should be able to run the example (in parallel)

docs/src/developers.md

@@ -50,7 +50,7 @@ For testing the C interface of libtrixi we rely on [GoogleTest](https://google.g
 The tests are contained in `cpp`-files located under `test/c`. They are processed by `cmake` and made available via
 `ctest`, provided the options
 ```
--DENABLE_TESTING=ON -DJULIA_PROJECT_PATH=<libtrixi-julia_directory>
+-DLIBTRIXI_ENABLE_TESTING=ON -DJULIA_PROJECT_PATH=<libtrixi-julia_directory>
 ```
 are passed to `cmake` during configuration.
 The executables can then be found under `<build_directory>/test/c` (they will not be installed). To run them, execute

docs/src/index.md

@@ -56,6 +56,8 @@ For building, `cmake` and its typical workflow is used.
     - Specifying the directory `install_directory` for later installation is optional.
     - Optional specification of build type sets some default compiler options for optimized
       or debug code.
+    - By default the Fortran-Interface is built; it may be excluded with
+      `-DLIBTRIXI_BUILD_FORTRAN_API=OFF`.
     - Building with t8code support is optional. It requires to pass
       `-DT8CODE_ROOT=<t8code_install_directory>`.
 
@@ -306,7 +308,7 @@ To try this out, perform the following steps:
     *using cmake*
     - Add
       ```
-      -DUSE_PACKAGE_COMPILER=ON -DJULIA_PROJECT_PATH=<libtrixi-julia_directory>
+      -DLIBTRIXI_USE_PACKAGE_COMPILER=ON -DJULIA_PROJECT_PATH=<libtrixi-julia_directory>
       ```
       to your cmake call (see above)
 3. From inside the `examples` folder you should be able to run the example (in parallel)

examples/CMakeLists.txt

@@ -17,6 +17,11 @@ if ( NOT T8CODE_FOUND )
     list( FILTER EXAMPLES EXCLUDE REGEX "trixi_controller_baroclinic.*" )
 endif()
 
+if (NOT LIBTRIXI_BUILD_FORTRAN_API)
+    # Remove Fortran files if the the Fortran API is not build
+    list( FILTER EXAMPLES EXCLUDE REGEX ".*\.f90" )
+endif()
+
 foreach ( EXAMPLE ${EXAMPLES} )
 
     get_filename_component ( EXAMPLE_EXT ${EXAMPLE} EXT )
@@ -41,7 +46,7 @@ foreach ( EXAMPLE ${EXAMPLES} )
         ${TARGET_NAME}
         PRIVATE MPI::MPI_${EXAMPLE_LANG} ${PROJECT_NAME}
     )
-    if ( NOT USE_PACKAGE_COMPILER )
+    if ( NOT LIBTRIXI_USE_PACKAGE_COMPILER )
         target_link_libraries( ${TARGET_NAME} PRIVATE ${PROJECT_NAME}_tls )
     endif()
     if ( T8CODE_FOUND )
@@ -53,7 +58,9 @@ foreach ( EXAMPLE ${EXAMPLES} )
         ${TARGET_NAME}
         PRIVATE ${CMAKE_SOURCE_DIR}/src
     )
-    if ( T8CODE_FOUND )
+
+    if ( LIBTRIXI_BUILD_FORTRAN_API AND T8CODE_FOUND )
+        # Add the t8code include directory of the Fortran module file
         target_include_directories( ${TARGET_NAME} PRIVATE ${T8CODE_ROOT}/include/t8_fortran_interface/ )
     endif()