Let user choose which filesystem lib (std/boost) to use

CMakeLists.txt

@@ -4,12 +4,60 @@
 # See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt
 
 cmake_minimum_required( VERSION 3.1 )
+if(${CMAKE_VERSION} VERSION_GREATER "3.8.0")
+    # Honor CXX_STANDARD_REQUIRED in check_cxx_source_compiles
+    # (see https://cmake.org/cmake/help/v3.8/policy/CMP0067.html)
+    cmake_policy( SET CMP0067 NEW )
+endif()
 
 project( boostdep LANGUAGES CXX )
 
+# Compile with c++17 if available (so we can use std::filesystem),
+# but boostdep is c++98 compatible, so no CMAKE_CXX_STANDARD_REQUIRED is necessary
+set( CMAKE_CXX_STANDARD 17 )
+
 add_executable( boostdep src/boostdep.cpp )
 
-find_package( Boost COMPONENTS filesystem REQUIRED )
-target_link_libraries( boostdep Boost::filesystem )
+####### options #######
+
+# Decide if boostdep should use Boost.Filesystem or std::filesystem
+
+# We default to using the standard library when available
+# and Boost.Filesystem otherwise
+# NOTE: Prior to 3.8.0 check_cxx_source_compiles will not honor the c++17 setting,
+#        so with older cmake versions this will never detect std::filesystem correctly
+include( CheckCXXSourceCompiles )
+check_cxx_source_compiles(
+"
+#include <filesystem>
+int main() {
+    std::filesystem::is_directory( std::filesystem::current_path() );
+}
+"
+has_std_filesystem )
+
+option( BOOSTDEP_USE_STD_FS "Use std::filesystem instead of boost::filesystem" ${has_std_filesystem} )
+
+#~~~~~~ options ~~~~~~
+
+if( BOOSTDEP_USE_STD_FS )
+
+    message(STATUS "Using std::filesystem as filesystem library")
+    target_compile_definitions( boostdep PUBLIC BOOSTDEP_USE_STD_FS )
+    target_link_libraries( boostdep PUBLIC stdc++fs )
+    # NOTE: Some compilers (e.g. g++-8) will require additional linker flags
+    #        in order to use std::filesystem (e.g. -lstdc++fs).
+    #        We are NOT handling those special cases
+
+else()
+
+    message(STATUS "Using Boost::filesystem as filesystem library")
+    if( NOT TARGET Boost::filesystem )
+        find_package( Boost COMPONENTS filesystem REQUIRED )
+    endif()
+    target_link_libraries( boostdep PUBLIC Boost::filesystem )
+
+endif()
+
 
 install( TARGETS boostdep RUNTIME DESTINATION bin )

src/boostdep.cpp

@@ -9,8 +9,6 @@
 
 #define _CRT_SECURE_NO_WARNINGS
 
-#include <boost/filesystem.hpp>
-#include <boost/filesystem/fstream.hpp>
 #include <string>
 #include <iostream>
 #include <fstream>
@@ -21,7 +19,16 @@
 #include <climits>
 #include <cstdlib>
 
-namespace fs = boost::filesystem;
+#ifdef BOOSTDEP_USE_STD_FS
+    #include <filesystem>
+    namespace fs = std::filesystem;
+#else
+    #include <boost/filesystem.hpp>
+    #include <boost/filesystem/fstream.hpp>
+    namespace fs = boost::filesystem;
+#endif
+
+
 
 // header -> module
 static std::map< std::string, std::string > s_header_map;
@@ -48,7 +55,7 @@ static void scan_module_headers( fs::path const & path )
 
         for( ; it != last; ++it )
         {
-            if( it->status().type() == fs::directory_file )
+            if( fs::is_directory( it->status() ) )
             {
                 continue;
             }
@@ -74,7 +81,7 @@ static void scan_submodules( fs::path const & path )
     {
         fs::directory_entry const & e = *it;
 
-        if( e.status().type() != fs::directory_file )
+        if( fs::is_directory( it->status() ) )
         {
             continue;
         }
@@ -209,7 +216,7 @@ static void scan_module_path( fs::path const & dir, bool remove_prefix, std::map
 
         for( ; it != last; ++it )
         {
-            if( it->status().type() == fs::directory_file )
+            if( fs::is_directory( it->status() ) )
             {
                 continue;
             }
@@ -221,7 +228,11 @@ static void scan_module_path( fs::path const & dir, bool remove_prefix, std::map
                 header = header.substr( n+1 );
             }
 
+#ifdef BOOSTDEP_USE_STD_FS
+            std::ifstream is( it->path() );
+#else
             fs::ifstream is( it->path() );
+#endif
 
             scan_header_dependencies( header, is, deps, from );
         }
@@ -1667,7 +1678,7 @@ static void add_module_headers( fs::path const & dir, std::set<std::string> & he
 
         for( ; it != last; ++it )
         {
-            if( it->status().type() == fs::directory_file )
+            if( fs::is_directory( it->status() ) )
             {
                 continue;
             }