Reverted the previous change regarding warnings aboit slicing excepti…

…ons.

Apparently, slicing was intentional, and the test verified that it worked.
This commit restores the previous behavior and disables the gcc warning
instead.

test/operations_test.cpp

@@ -291,6 +291,12 @@ namespace
 
   //  exception_tests()  ---------------------------------------------------------------//
 
+#if defined(BOOST_GCC) && BOOST_GCC >= 80000
+#pragma GCC diagnostic push
+// catching polymorphic type "X" by value - that's the intention of the test
+#pragma GCC diagnostic ignored "-Wcatch-value"
+#endif
+
   void exception_tests()
   {
     cout << "exception_tests..." << endl;
@@ -304,7 +310,7 @@ namespace
     {
       fs::create_directory("no-such-dir/foo/bar");
     }
-    catch (std::runtime_error& x)
+    catch (std::runtime_error x)
     {
       exception_thrown = true;
       if (report_throws) cout << x.what() << endl;
@@ -325,7 +331,7 @@ namespace
     {
       fs::create_directory("no-such-dir/foo/bar");
     }
-    catch (system_error& x)
+    catch (system_error x)
     {
       exception_thrown = true;
       if (report_throws) cout << x.what() << endl;
@@ -343,7 +349,7 @@ namespace
     {
       fs::create_directory("no-such-dir/foo/bar");
     }
-    catch (fs::filesystem_error& x)
+    catch (fs::filesystem_error x)
     {
       exception_thrown = true;
       if (report_throws) cout << x.what() << endl;
@@ -368,7 +374,7 @@ namespace
     {
       fs::create_directory("no-such-dir/foo/bar");
     }
-    catch (fs::filesystem_error& x)
+    catch (const fs::filesystem_error& x)
     {
       exception_thrown = true;
       if (report_throws) cout << x.what() << endl;
@@ -407,6 +413,10 @@ namespace
     cout << "  exception_tests complete" << endl;
   }
 
+#if defined(BOOST_GCC) && BOOST_GCC >= 80000
+#pragma GCC diagnostic pop
+#endif
+
   // create a directory tree that can be used by subsequent tests  ---------------------//
   //
   //    dir