🐛 Fix mipi catalog payload size calculation

Problem:
- When logging runtime arguments whose total size is less than 2
  `std::uint32_t`s, the mipi builder uses the `log_by_args` path, despite the
  fact that packing the arguments according to the mipi spec means they could
  use much more space.

Solution:
- Calculate the size based on the packed space, not the original argument size.

Author: elbeno

include/log/catalog/mipi_builder.hpp

@@ -67,22 +67,20 @@ template <packer P> struct builder<defn::catalog_msg_t, P> {
     template <auto Level, typename... Ts>
     static auto build(string_id id, module_id m, Ts... args) {
         using namespace msg;
-        if constexpr ((0 + ... + sizeof(Ts)) <= sizeof(std::uint32_t) * 2) {
+        constexpr auto payload_size =
+            (sizeof(id) + ... + sizeof(typename P::template pack_as_t<Ts>));
+        if constexpr (payload_size <= sizeof(uint32_t) * 3) {
             constexpr auto header_size =
                 defn::catalog_msg_t::size<std::uint32_t>::value;
-            constexpr auto payload_size =
-                stdx::sized8{(sizeof(id) + ... +
-                              sizeof(typename P::template pack_as_t<Ts>))}
-                    .in<std::uint32_t>();
             using storage_t =
-                std::array<std::uint32_t, header_size + payload_size>;
+                std::array<std::uint32_t,
+                           header_size +
+                               stdx::sized8{payload_size}.in<std::uint32_t>()>;
             return catalog_builder<storage_t, P>{}.template build<Level>(
                 id, m, args...);
         } else {
             constexpr auto header_size =
                 defn::catalog_msg_t::size<std::uint8_t>::value;
-            constexpr auto payload_size =
-                (sizeof(id) + ... + sizeof(typename P::template pack_as_t<Ts>));
             using storage_t =
                 std::array<std::uint8_t, header_size + payload_size>;
             return catalog_builder<storage_t, P>{}.template build<Level>(

test/log/encoder.cpp

@@ -259,6 +259,17 @@ TEST_CASE("log more than two arguments", "[mipi]") {
     }
 }
 
+TEST_CASE("log more than two arguments whose size fits in two uint32_ts",
+          "[mipi]") {
+    CIB_LOG_ENV(logging::get_level, logging::level::TRACE);
+    test_critical_section::count = 0;
+    auto cfg = logging::binary::config{
+        test_log_buf_destination<logging::level::TRACE, log_env, 42u, 'a', 'b',
+                                 'c'>{}};
+    cfg.logger.log_msg<log_env>(stdx::ct_format<"{} {} {}">('a', 'b', 'c'));
+    CHECK(test_critical_section::count == 2);
+}
+
 TEST_CASE("log to multiple destinations", "[mipi]") {
     CIB_LOG_ENV(logging::get_level, logging::level::TRACE);
     test_critical_section::count = 0;