added BUILD_<SHARED|STATIC>_LIBS options and comments

CMakeLists.txt

@@ -2,39 +2,67 @@ cmake_minimum_required(VERSION 3.16)
 
 # =========== SETUP THE PROJECT =============
 
+# Initialize the CMake project.
 project(Trexio 
 	VERSION 2.0.0 
 	DESCRIPTION "TREX I/O library" 
 	LANGUAGES C Fortran
 	)
 
+# Request the C99 standard.
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_C_STANDARD_REQUIRED ON)
 
+# By default, the shared TREXIO library is built (even without -DBUILD_SHARED_LIBS=ON).
+# To change this behaviour, append -DBUILD_STATIC_LIBS=ON to the cmake call.
+option(BUILD_SHARED_LIBS "Build the shared library" ON)
+option(BUILD_STATIC_LIBS "Build the static library" OFF)
+
+if(BUILD_SHARED_LIBS AND BUILD_STATIC_LIBS)
+  set(BUILD_SHARED_LIBS OFF)
+endif()
+
 # ========= DEFINE TREXIO C LIBRARY ========= 
 
-#IF DO_SHARED
-add_library(trexio SHARED
+# Set a list of TREXIO source files that are always compiled.
+set(TREXIO_SOURCES 
 	src/trexio.c
 	src/trexio_text.c
 	)
-#ELIF DO_STATIC
 
-#ENDIF
+# Conditional SHARED/STATIC build for TREXIO library.
+if(BUILD_SHARED_LIBS AND NOT BUILD_STATIC_LIBS)
 
+  message(STATUS "TREXIO :: shared C library will be built")
+  add_library(trexio SHARED ${TREXIO_SOURCES})
+
+elseif(NOT BUILD_SHARED_LIBS AND BUILD_STATIC_LIBS)
+  
+  message(STATUS "TREXIO :: static C library will be built")
+  add_library(trexio STATIC ${TREXIO_SOURCES})
+
+else()
+  message(FATAL_ERROR "Building both static and shared TREXIO simultaneously is not supported.")
+endif()
+
+# Set TREXIO version and include files.
 set_target_properties(trexio PROPERTIES 
 	VERSION ${PROJECT_VERSION}
 	PUBLIC_HEADER include/trexio.h
 	)
 
+# Set directories to be included at build time.
 target_include_directories(trexio PRIVATE src)
 include_directories(include)
 
 # ============= CONFIGURE HDF5 ============== 
 
+# By default TREXIO is configured with HDF5 support.
+# To change this, append -DENABLE-HDF5=OFF to the cmake call.
 option(ENABLE_HDF5 "Enable HDF5 support" ON)
 
 if(ENABLE_HDF5)
+  # Try to detect HDF5 installation using built-in FindHDF5.cmake macro.
   find_package(HDF5 REQUIRED COMPONENTS C HL)
 
   if(HDF5_FOUND)
@@ -44,13 +72,18 @@ if(ENABLE_HDF5)
   else()
     # Download and install HDF5 library using FetchContent
     # ...
-    # For now - raise a FatalError
-    message(FATAL_ERROR "HDF5 is enabled not found.")
+    # For now - raise a FATAL_ERROR
+    message(FATAL_ERROR "HDF5 is enabled but not found.")
   endif()
 
+  # If HDF5 found:
+  # - append the trexio_hdf5.c source file with the HDF5 back end
   target_sources(trexio PRIVATE src/trexio_hdf5.c)
+  # - define symbol HAVE_HDF5=1 (use to activate HDF5 back end in the preprocessor conditionals)
   target_compile_definitions(trexio PUBLIC HAVE_HDF5=1)
+  # - include dirs with HDF5 header files
   target_include_directories(trexio PRIVATE ${HDF5_C_INCLUDE_DIRS})
+  # - link to HDF5 C libraries
   target_link_libraries(trexio PRIVATE 
 	  ${HDF5_C_HL_LIBRARIES} 
 	  ${HDF5_C_LIBRARIES})
@@ -60,7 +93,7 @@ endif()
 
 enable_testing()
 
-# create the lists of tests
+# Create a list of tests for TEXT back end.
 set(Tests_text
   open_text
   io_dset_float_text
@@ -73,6 +106,7 @@ set(Tests_text
   )
 
 if(ENABLE_HDF5)
+# Create a list of tests for HDF5 back end.
   set(Tests_hdf5
     open_hdf5
     io_dset_float_hdf5
@@ -83,12 +117,14 @@ if(ENABLE_HDF5)
     io_str_hdf5
     overwrite_all_hdf5
     )
+
+# Set ${Tests} variable to the complete list of tests.
   set(Tests io_all ${Tests_text} ${Tests_hdf5})
 else()
   set(Tests ${Tests_text})
 endif()
 
-# Add all the ADD_TEST for each test
+# Compile each TREXIO test as an executable and add them to CTest using add_test
 foreach(test ${Tests})
   add_executable(${test} tests/${test}.c)
   target_link_libraries(${test} PRIVATE trexio)
@@ -98,6 +134,8 @@ endforeach ()
 # ============= INSTALL TREXIO ============== 
 
 include(GNUInstallDirs)
+# Use standard GNU directories for installation of TREXIO (e.g. /usr/local/lib|include).
+# The installation prefix can be modified using -DCMAKE_INSTALL_PREFIX=<custom/path> option of cmake.
 install(TARGETS trexio
     LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
     PUBLIC_HEADER DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}