EBO for multiset and multimap

untests/flat_multiset_tests.cpp

@@ -70,6 +70,16 @@ namespace
         return !(l == r);
     }
 
+    template < typename T >
+    class dummy_less {
+    public:
+        dummy_less(int i) : i(i) {}
+        bool operator()(const T& l, const T& r) const {
+            return l < r;
+        }
+        int i = 0;
+    };
+
     template < typename T >
     constexpr std::add_const_t<T>& my_as_const(T& t) noexcept {
         return t;
@@ -77,6 +87,14 @@ namespace
 }
 
 TEST_CASE("flat_multiset") {
+    SECTION("sizeof") {
+        REQUIRE(sizeof(flat_multiset<int>) == sizeof(std::vector<int>));
+
+        struct vc : flat_multiset<int>::value_compare {
+            int i;
+        };
+        REQUIRE(sizeof(vc) == sizeof(int));
+    }
     SECTION("types") {
         using set_t = flat_multiset<int>;
 
@@ -392,6 +410,16 @@ TEST_CASE("flat_multiset") {
         REQUIRE(my_as_const(s0).key_comp().i == 42);
         REQUIRE(my_as_const(s0).value_comp().i == 42);
     }
+    SECTION("custom_less") {
+        using set_t = flat_multiset<int, dummy_less<int>>;
+        auto s0 = set_t(dummy_less<int>(42));
+        auto s1 = set_t(dummy_less<int>(21));
+        REQUIRE(s0.key_comp().i == 42);
+        REQUIRE(s1.key_comp().i == 21);
+        s0.swap(s1);
+        REQUIRE(s0.key_comp().i == 21);
+        REQUIRE(s1.key_comp().i == 42);
+    }
     SECTION("operators") {
         using set_t = flat_multiset<int>;