caster_odr unnamed namespace translation_unit_tag experiment

Author: rwgk

caster_odr/car.cc

@@ -0,0 +1,18 @@
+#include "engine.h"
+
+namespace engine {
+
+template <>
+struct specs<short> {
+  int power() const { return 100; }
+};
+
+template <>
+struct specs<long> {
+  int power() const { return 200; }
+};
+
+}  // namespace engine
+
+int short_car_power() { return engine::power<short>(); }
+int long_car_power() { return engine::power<long>(); }

caster_odr/compile_and_run.sh

@@ -0,0 +1,7 @@
+set -e
+set -x
+clang++ -std=c++11 car.cc truck.cc vehicle_specs.cc && a.out
+clang++ -std=c++11 truck.cc car.cc vehicle_specs.cc && a.out
+clang++ -std=c++11 -DUSE_TRANSLATION_UNIT_TAG car.cc truck.cc vehicle_specs.cc && a.out
+clang++ -std=c++11 -DUSE_TRANSLATION_UNIT_TAG truck.cc car.cc vehicle_specs.cc && a.out
+rm a.out

caster_odr/engine.h

@@ -0,0 +1,23 @@
+namespace engine {
+
+#ifdef USE_TRANSLATION_UNIT_TAG
+namespace {
+struct translation_unit_tag {};
+}  // namespace
+
+template <typename T, typename = translation_unit_tag>
+#else
+template <typename T>
+#endif
+struct specs;
+
+#ifdef USE_TRANSLATION_UNIT_TAG
+template <typename T, typename = translation_unit_tag>
+#else
+template <typename T>
+#endif
+int power() {
+  return specs<T>().power();
+}
+
+}  // namespace engine

caster_odr/truck.cc

@@ -0,0 +1,18 @@
+#include "engine.h"
+
+namespace engine {
+
+template <>
+struct specs<short> {
+  int power() const { return 300; }
+};
+
+template <>
+struct specs<long> {
+  int power() const { return 400; }
+};
+
+}  // namespace engine
+
+int short_truck_power() { return engine::power<short>(); }
+int long_truck_power() { return engine::power<long>(); }

caster_odr/vehicle_specs.cc

@@ -0,0 +1,14 @@
+#include <iostream>
+
+int short_car_power();
+int long_car_power();
+int short_truck_power();
+int long_truck_power();
+
+int main() {
+  std::cout << "short car   power:   " << short_car_power() << std::endl;
+  std::cout << "long  car   power:   " << long_car_power() << std::endl;
+  std::cout << "short truck power:   " << short_truck_power() << std::endl;
+  std::cout << "long  truck power:   " << long_truck_power() << std::endl;
+  return 0;
+}