Copy functionality to check for fs libraries from dd4hep

Make podio look for a compatible filesystem library itself during the
cmake stage, eventually falling back to boost in case the compiler
doesn't support it natively.

CMakeLists.txt

@@ -71,8 +71,6 @@ option(CREATE_DOC "Whether or not to create doxygen doc target." OFF)
 option(ENABLE_SIO "Build the SIO block handlers and readers and writers." OFF)
 
 
-option(USE_BOOST_FS "Use the boost filesystem library (in case your system does not yet have it)" OFF)
-
 #--- Declare ROOT dependency ---------------------------------------------------
 list(APPEND CMAKE_PREFIX_PATH $ENV{ROOTSYS})
 set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
@@ -84,18 +82,19 @@ if(ROOT_VERSION VERSION_LESS 6.14)
 endif()
 list(APPEND PODIO_IO_HANDLERS ROOT)
 
-#--- optionally build with SIO -------------------------------------------------
+#--- enable podio macros--------------------------------------------------------
+include(cmake/podioMacros.cmake)
+
+# optionally build with SIO -------------------------------------------------
 if(ENABLE_SIO)
   find_package( SIO REQUIRED)
+  PODIO_CHECK_CPP_FS(PODIO_FS_LIBS)
   if (SIO_FOUND)
     MESSAGE( STATUS "Found SIO library - will build SIO I/O support" )
     list(APPEND PODIO_IO_HANDLERS SIO)
   endif()
 endif()
 
-#--- enable podio macros--------------------------------------------------------
-include(cmake/podioMacros.cmake)
-
 #--- enable unit testing capabilities ------------------------------------------
 include(CTest)
 

cmake/podioMacros.cmake

@@ -151,3 +151,40 @@ function(PODIO_GENERATE_DATAMODEL datamodel YAML_FILE RETURN_HEADERS RETURN_SOUR
     )
 
 endfunction()
+
+#---------------------------------------------------------------------------------------------------
+function(PODIO_CHECK_CPP_FS FS_LIBS)
+  SET(${have_filesystem} FALSE)
+  MESSAGE(VERBOSE "Checking for filesystem support of compiler")
+  # GNU implementation prior to 9.1 requires linking with -lstdc++fs and LLVM
+  # implementation prior to LLVM 9.0 requires linking with -lc++fs
+  # After that it should be built-in
+  FOREACH(FS_LIB_NAME "" stdc++fs c++fs)
+    MESSAGE(VERBOSE "Linking against ${FS_LIB_NAME}")
+    try_compile(have_filesystem ${CMAKE_BINARY_DIR}/try ${PROJECT_SOURCE_DIR}/cmake/try_filesystem.cpp
+      CXX_STANDARD ${CMAKE_CXX_STANDARD}
+      CXX_EXTENSIONS False
+      OUTPUT_VARIABLE HAVE_FS_OUTPUT
+      LINK_LIBRARIES ${FS_LIB_NAME}
+      )
+    MESSAGE(DEBUG "-----> " ${HAVE_FS_OUTPUT})
+    IF(have_filesystem)
+      MESSAGE(VERBOSE "Compiler supports filesystem when linking against ${FS_LIB_NAME}")
+      SET(${FS_LIBS} ${FS_LIB_NAME} PARENT_SCOPE)
+      BREAK()
+    ENDIF()
+    MESSAGE("Compiler not compatible when linking against ${FS_LIB_NAME}")
+  ENDFOREACH()
+
+  IF(NOT have_filesystem)
+    MESSAGE(STATUS "Compiler does not have filesystem support, falling back to boost::filesystem")
+    find_package(Boost REQUIRED COMPONENTS filesystem system)
+    SET(${FS_LIBS} Boost::filesystem Boost::system PARENT_SCOPE)
+    SET_TARGET_PROPERTIES(Boost::filesystem
+      PROPERTIES
+      INTERFACE_COMPILE_DEFINITIONS USE_BOOST_FILESYSTEM
+    )
+  GET_TARGET_PROPERTY(BOOST_FILESYSTEM_LOC Boost::filesystem IMPORTED_LOCATION)
+  GET_FILENAME_COMPONENT(BOOST_DIR ${BOOST_FILESYSTEM_LOC} DIRECTORY)
+  ENDIF()
+endfunction()

cmake/try_filesystem.cpp

@@ -0,0 +1,12 @@
+#include <iostream>
+#include <filesystem>
+
+int main(int, char**) {
+  namespace fs = std::filesystem;
+
+  for (const auto& file : fs::directory_iterator("./")) {
+    std::cout << file.path() << ": " << file.file_size() << '\n';
+  }
+
+  return 0;
+}

src/CMakeLists.txt

@@ -58,29 +58,14 @@ target_sources(podioDict PRIVATE podioDict.cxx)
 
 # SIO I/O library
 if(ENABLE_SIO)
-
-  if( USE_BOOST_FS )
-    find_package(boost)
-    add_definitions(-D USE_BOOST_FS)
-  endif()
-
   add_library(podioSioIO SHARED ${sio_sources})
   add_library(podio::podioSioIO ALIAS podioSioIO)
 
-  if(USE_BOOST_FS)
-    target_include_directories(podioSioIO PUBLIC
-      $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
-      $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
-      ${SIO_INCLUDE_DIRS}
-      ${BOOST_INCLUDE_DIR})
-    target_link_libraries(podioSioIO PUBLIC podio::podio ${SIO_LIBRARIES} ${CMAKE_DL_LIBS} boost_filesystem)
-  else()
-    target_include_directories(podioSioIO PUBLIC
-      $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
-      $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
-      ${SIO_INCLUDE_DIRS})
-    target_link_libraries(podioSioIO PUBLIC podio::podio ${SIO_LIBRARIES} ${CMAKE_DL_LIBS})
-  endif()
+  target_include_directories(podioSioIO PUBLIC
+    $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
+    $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
+    ${SIO_INCLUDE_DIRS})
+  target_link_libraries(podioSioIO PUBLIC podio::podio ${SIO_LIBRARIES} ${CMAKE_DL_LIBS} ${PODIO_FS_LIBS})
 
   LIST(APPEND INSTALL_LIBRARIES podioSioIO)
 endif()

src/SIOBlock.cc

@@ -4,7 +4,7 @@
 #include <dlfcn.h>
 #include <cstdlib>
 #include <sstream>
-#ifdef USE_BOOST_FS
+#ifdef USE_BOOST_FILESYSTEM
  #include <boost/filesystem.hpp>
 #else
  #include <filesystem>
@@ -152,7 +152,7 @@ namespace podio {
   }
 
   std::vector<std::string> SIOBlockLibraryLoader::getLibNames() {
-#ifdef USE_BOOST_FS
+#ifdef USE_BOOST_FILESYSTEM
     namespace fs = boost::filesystem;
 #else
     namespace fs = std::filesystem;