Replace boost::filesystem by std::experimental::filesystem when the later is available

CMakeLists.txt

@@ -752,11 +752,27 @@ endif()
 
 
 
+################################################################################
+# Log4cpp - http://log4cpp.sourceforge.net/
+################################################################################
+find_package(LOG4CPP)
+set_package_properties(LOG4CPP PROPERTIES
+    URL "http://log4cpp.sourceforge.net/"
+    DESCRIPTION "Library of C++ classes for flexible logging to files"
+    PURPOSE "Required by GNU Radio."
+    TYPE REQUIRED
+)
+if(NOT LOG4CPP_FOUND)
+    message(FATAL_ERROR "*** Log4cpp is required to build gnss-sdr")
+endif()
+
+
+
 ################################################################################
 # Dectect availability of std::filesystem
 ################################################################################
 set(FILESYSTEM_FOUND FALSE)
-if(NOT (GNURADIO_VERSION VERSION_LESS 3.8))
+if(NOT (GNURADIO_VERSION VERSION_LESS 3.8) AND LOG4CPP_READY_FOR_CXX17)
     # Check if we have std::filesystem
     if(NOT (CMAKE_VERSION VERSION_LESS 3.8))
         if(POLICY CMP0057)
@@ -910,22 +926,6 @@ endif()
 
 
 
-################################################################################
-# Log4cpp - http://log4cpp.sourceforge.net/
-################################################################################
-find_package(LOG4CPP)
-set_package_properties(LOG4CPP PROPERTIES
-    URL "http://log4cpp.sourceforge.net/"
-    DESCRIPTION "Library of C++ classes for flexible logging to files"
-    PURPOSE "Required by GNU Radio."
-    TYPE REQUIRED
-)
-if(NOT LOG4CPP_FOUND)
-    message(FATAL_ERROR "*** Log4cpp is required to build gnss-sdr")
-endif()
-
-
-
 ################################################################################
 # volk_gnsssdr module - GNSS-SDR's own VOLK library
 ################################################################################

cmake/Modules/FindLOG4CPP.cmake

@@ -39,6 +39,20 @@ find_path(LOG4CPP_INCLUDE_DIR log4cpp/Category.hh
   $ENV{LOG4CPP_ROOT}/include
 )
 
+if(LOG4CPP_INCLUDE_DIR)
+    file(STRINGS ${LOG4CPP_INCLUDE_DIR}/log4cpp/Priority.hh _log4cpp_Priority)
+    set(_log4cpp_cxx17 TRUE)
+    foreach(_loop_var IN LISTS _log4cpp_Priority)
+        string(STRIP "${_loop_var}" _file_line)
+        if("throw(std::invalid_argument);" STREQUAL "${_file_line}")
+            set(_log4cpp_cxx17 FALSE)
+        endif()
+    endforeach()
+    if(${_log4cpp_cxx17})
+        set(LOG4CPP_READY_FOR_CXX17 TRUE)
+    endif()
+endif()
+
 set(LOG4CPP_NAMES log4cpp)
 find_library(LOG4CPP_LIBRARY
   NAMES ${LOG4CPP_NAMES}

src/algorithms/libs/gnss_sdr_flags.cc

@@ -43,7 +43,7 @@ namespace fs = std::experimental::filesystem;
 namespace fs = std::filesystem;
 #endif
 #else
-#include <boost/filesystem/path.hpp>
+#include <boost/filesystem/operations.hpp>  // for exists
 namespace fs = boost::filesystem;
 #endif