Fix compiling with C++17 + Clang 5 + libstdc++ v5

This basically tests the combination where the compiler supports most
of C++17 but the library does not.

.travis.yml

@@ -61,6 +61,13 @@ matrix:
               packages: ['clang-5.0']
       env: COMPILER='clang++-5.0' CPP14=1
 
+    - os: linux
+      compiler: clang
+      addons:
+          apt:
+              sources: *all_sources
+              packages: ['clang-5.0']
+      env: COMPILER='clang++-5.0' CPP17=1
 
     - os: linux
       compiler: clang

src/catch2/internal/catch_compiler_capabilities.hpp

@@ -222,7 +222,7 @@
   // Check if byte is available and usable
   #  if __has_include(<cstddef>) && defined(CATCH_CPP17_OR_GREATER)
   #    include <cstddef>
-  #    if __cpp_lib_byte > 0
+  #    if defined(__cpp_lib_byte) && (__cpp_lib_byte > 0)
   #      define CATCH_INTERNAL_CONFIG_CPP17_BYTE
   #    endif
   #  endif // __has_include(<cstddef>) && defined(CATCH_CPP17_OR_GREATER)

src/catch2/matchers/catch_matchers_templated.hpp

@@ -55,11 +55,11 @@ namespace Matchers {
             return arr;
         }
 
-        #ifdef CATCH_CPP17_OR_GREATER
+#if defined( __cpp_lib_logical_traits ) && __cpp_lib_logical_traits >= 201510
 
         using std::conjunction;
 
-        #else // CATCH_CPP17_OR_GREATER
+#else // __cpp_lib_logical_traits
 
         template<typename... Cond>
         struct conjunction : std::true_type {};
@@ -67,7 +67,7 @@ namespace Matchers {
         template<typename Cond, typename... Rest>
         struct conjunction<Cond, Rest...> : std::integral_constant<bool, Cond::value && conjunction<Rest...>::value> {};
 
-        #endif // CATCH_CPP17_OR_GREATER
+#endif // __cpp_lib_logical_traits
 
         template<typename T>
         using is_generic_matcher = std::is_base_of<

tests/SelfTest/UsageTests/Generators.tests.cpp

@@ -62,12 +62,12 @@ TEST_CASE("tables", "[generators]") {
 
 // Structured bindings make the table utility much nicer to use
 TEST_CASE( "strlen2", "[approvals][generators]" ) {
-    auto [test_input, expected] = GENERATE( table<std::string, size_t>({
-            {"one", 3},
-            {"two", 3},
-            {"three", 5},
-            {"four", 4}
-        }));
+    using tuple_type = std::tuple<std::string, int>; // see above workaround
+    auto [test_input, expected] =
+        GENERATE( table<std::string, size_t>( { tuple_type{ "one", 3 },
+                                                tuple_type{ "two", 3 },
+                                                tuple_type{ "three", 5 },
+                                                tuple_type{ "four", 4 } } ) );
 
     REQUIRE( test_input.size() == expected );
 }
@@ -103,11 +103,9 @@ TEST_CASE( "strlen3", "[generators]" ) {
 static auto eatCucumbers( int start, int eat ) -> int { return start-eat; }
 
 SCENARIO("Eating cucumbers", "[generators][approvals]") {
-
-    auto [start, eat, left] = GENERATE( table<int,int,int> ({
-            { 12, 5, 7 },
-            { 20, 5, 15 }
-        }));
+    using tuple_type = std::tuple<int, int, int>;
+    auto [start, eat, left] = GENERATE( table<int, int, int>(
+        { tuple_type{ 12, 5, 7 }, tuple_type{ 20, 5, 15 } } ) );
 
     GIVEN( "there are " << start << " cucumbers" )
     WHEN( "I eat " << eat << " cucumbers" )