MessagePack reader: reject an array/map 32 length equal to SIZE_MAX

On a platform with a 32-bit std::size_t, an array 32 or map 32 length of
0xFFFFFFFF equals unknown_size(), so start_array()/start_object() were
told the size was unknown and skipped the max_size() check. Route both
through the CBOR length check, renamed get_container_size(), which
already rejects that value.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

tests/src/unit-32bit.cpp

@@ -97,3 +97,23 @@ TEST_CASE("CBOR")
         }
     }
 }
+
+TEST_CASE("MessagePack")
+{
+    SECTION("parse errors")
+    {
+        SECTION("array/map size equal to the unknown-size sentinel")
+        {
+            // on 32-bit platforms an array 32/map 32 length of 0xFFFFFFFF aliases unknown_size()
+            std::vector<uint8_t> const varr = {0xDD, 0xFF, 0xFF, 0xFF, 0xFF};
+            std::vector<uint8_t> const vmap = {0xDF, 0xFF, 0xFF, 0xFF, 0xFF};
+
+            json _;
+            CHECK_THROWS_WITH_AS(_ = json::from_msgpack(varr), "[json.exception.out_of_range.408] syntax error while parsing MessagePack size: excessive array size", json::out_of_range&);
+            CHECK(json::from_msgpack(varr, true, false).is_discarded());
+
+            CHECK_THROWS_WITH_AS(_ = json::from_msgpack(vmap), "[json.exception.out_of_range.408] syntax error while parsing MessagePack size: excessive map size", json::out_of_range&);
+            CHECK(json::from_msgpack(vmap, true, false).is_discarded());
+        }
+    }
+}

tests/src/unit-regression2.cpp

@@ -1005,7 +1005,7 @@ TEST_CASE("regression test - excessive binary container size honors allow_except
     // allow_exceptions=true (the default) must still throw exactly as before.
     // The exact message text is not checked here: on platforms where
     // std::size_t is 32-bit, the CBOR reader's own length-narrowing check
-    // (get_cbor_container_size(), unrelated to this fix) intercepts a
+    // (get_container_size(), unrelated to this fix) intercepts a
     // declared length of 2^63 before it ever reaches the check this test
     // targets, with different (but equally valid, and already correct)
     // wording -- see unit-cbor.cpp for coverage of that message.