Fix errors on compilation with c++17

CMakeLists.txt

@@ -38,8 +38,8 @@ endif()
 # Using span from std
 if (NOT UUID_USING_CXX20_SPAN)
     target_include_directories(${PROJECT_NAME} INTERFACE
-            $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/gsl>
-            $<INSTALL_INTERFACE:include/gsl>)
+            $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
+            $<INSTALL_INTERFACE:include>)
     install(DIRECTORY gsl DESTINATION include)
 endif ()
 
@@ -70,4 +70,4 @@ export(EXPORT ${PROJECT_NAME}-targets
 if (UUID_BUILD_TESTS)
     enable_testing()
     add_subdirectory(test)
-endif ()
+endif ()

include/uuid.h

@@ -16,7 +16,21 @@
 #include <chrono>
 #include <numeric>
 #include <atomic>
+
+#ifdef __cplusplus
+
+#  if (__cplusplus >= 202002L) || (defined(_MSVC_LANG) && _MSVC_LANG >= 202002L)
+#    define LIBUUID_CPP20_OR_GREATER
+#  endif
+
+#endif
+
+
+#ifdef LIBUUID_CPP20_OR_GREATER
 #include <span>
+#else
+#include <gsl/gsl>
+#endif
 
 #ifdef _WIN32
 
@@ -950,4 +964,4 @@ namespace std
    };
 }
 
-#endif /* STDUUID_H */
+#endif /* STDUUID_H */

test/CMakeLists.txt

@@ -28,4 +28,4 @@ set_tests_properties("test_${PROJECT_NAME}"
         FAIL_REGULAR_EXPRESSION "Failed \\d+ test cases")
 set_tests_properties("test_${PROJECT_NAME}"
         PROPERTIES
-        TIMEOUT 120)
+        TIMEOUT 120)