Ensure mp-units are compatible with std::atomic

test/runtime/CMakeLists.txt

@@ -24,7 +24,7 @@ cmake_minimum_required(VERSION 3.5)
 
 find_package(Catch2 3 REQUIRED)
 
-add_executable(unit_tests_runtime distribution_test.cpp fmt_test.cpp math_test.cpp)
+add_executable(unit_tests_runtime distribution_test.cpp fmt_test.cpp math_test.cpp atomic_test.cpp)
 if(${projectPrefix}BUILD_CXX_MODULES)
     target_compile_definitions(unit_tests_runtime PUBLIC ${projectPrefix}MODULES)
 endif()

test/runtime/atomic_test.cpp

@@ -0,0 +1,41 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2024 Nick Thompson
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#include <catch2/catch_all.hpp>
+#include <mp-units/math.h>
+#include <mp-units/ostream.h>
+#include <mp-units/systems/angular/angular.h>
+#include <mp-units/systems/isq/space_and_time.h>
+#include <mp-units/systems/si/unit_symbols.h>
+#include <mp-units/systems/si/units.h>
+#include <limits>
+#include <atomic>
+
+using namespace mp_units;
+using namespace mp_units::si::unit_symbols;
+
+TEST_CASE("std::atomic works with dimensioned types", "[atomic][assignment]")
+{
+  std::atomic<isq::area[m2]> a = 3.0*isq::area[m2];
+  std::atomic<isq::area[m2]> b = 3.0*isq::area[m2];
+  REQUIRE(a == b);
+}