support bazel complie this project and format code.

learn_class/modern_cpp_30/obj/all.cpp

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+//
+// Created by light on 19-12-23.
+//
+
+#include <iostream>
+#include <string>
+#include <vector>
+
+struct Test {
+  Test() {
+    // std::cout << "construct a Test object" << std::endl;
+  }
+
+  Test(const Test &) {
+    std::cout << "copy construct  a Test object" << std::endl;
+  }
+
+  Test &operator=(const Test &t) {
+    std::cout << "copy assignment a Test object" << std::endl;
+    return *this;
+  }
+
+  Test(Test &&t) { std::cout << "move construct a Test object" << std::endl; }
+
+  Test &operator=(Test &&t) {
+    std::cout << "move assignment a Test object" << std::endl;
+    return *this;
+  }
+
+  ~Test() {
+    // std::cout << "destruct a Test object" << std::endl;
+  }
+};
+
+Test getTest() {
+  // anonymous object
+  return Test();
+}
+
+Test getTestWithName() {
+  // named return value
+  Test temp;
+  return temp;
+}
+/**
+ * 1.copy
+ * construct本身在RVO和NRVO两种情况下被优化了，如果再加上move反而画蛇添足。
+ * 2.加入了move assignment后，默认是调用move assignment而不是copy
+ * assignment，可以将move assignment注释后测试。
+ * 3.对于RVO和NRVO来说，construction的情况编译器优化得比较好了，加入move语义主要是对于assignment有比较大影响
+ */
+int main() {
+  std::cout << "==== common case ====" << std::endl;
+  Test o1;
+  std::cout << "---- Test copy construct: " << std::endl;
+  Test o2(o1); // two ways for copy construct
+  Test o3 = o1;
+  std::cout << "---- Test move construct: " << std::endl;
+  Test o4(std::move(o3));
+  std::cout << "---- Test assignment: " << std::endl;
+  o2 = o1;
+  std::cout << "---- Test move assignment: " << std::endl;
+  Test o5;
+  o5 = std::move(o4);
+
+  std::cout << "\n==== test for rvo ===" << std::endl;
+  std::cout << "---- Test rvo for copy construct: " << std::endl;
+  Test obj11(getTest());
+  Test obj1 = getTest();
+  std::cout << "---- Test rvo for move construct: " << std::endl;
+  Test obj12(std::move(getTest()));
+  std::cout << "---- Test rvo for assignment: " << std::endl;
+  Test obj2;
+  obj2 = getTest();
+  std::cout << "---- Test rvo move assignment: " << std::endl;
+  Test obj5;
+  obj5 = std::move(getTest());
+
+  std::cout << "\n==== test for nrvo ===" << std::endl;
+  std::cout << "---- Test nrvo for copy construct: " << std::endl;
+  Test obj33(getTestWithName());
+  Test obj3 = getTestWithName();
+  std::cout << "---- Test nrvo for move construct: " << std::endl;
+  Test obj34(std::move(getTestWithName()));
+  std::cout << "---- Test nrvo for assignment: " << std::endl;
+  Test obj4;
+  obj4 = getTestWithName();
+  std::cout << "---- Test nrvo move assignment: " << std::endl;
+  Test obj6;
+  obj6 = std::move(getTestWithName());
+
+  return 0;
+}