domiyanyue

class WrapperA{
public:
  A *p;
  WrapperA(){
     p = new A;
  }
  ~WrapperA(){
    delete p;
  }
};

domiyanyue

int mem_demo_static(){
  A a;
  return a.func(); 
  // A's destructor is called automatically
}

int mem_demo_dynamic(){
  A* a = new A;
  return a->func(); 
  // A's destructor is not called, memory leak!

domiyanyue

class A {
public:
   A(int n){
      array = new int[n];
   }
   ~A(){
     delete array;
   }
private:
  int *array;

domiyanyue

int demo3(){
  A *a = new A;
  int ra = a -> func();
  if(ra == 2) {
    try {
      B *b = new B;
    }
    catch (...)
    {
      delete a;

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int demo2(){
  A *a = new A;
  int ra = a -> func();
  if(ra == 2) {
    B *b = new B;
    int rb = b->func();
    delete a;
    delete b;
    return rb;
    

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int demo1(){
  A *a = new A();
  int r = a -> func();
  delete a;
  return r; 
}

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g++ main.o -L. -lmy_math -o a.out -Wl,-rpath,/home/cpp_tutorial/static_library
./a.out
0.5

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export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/cpp_tutorial/static_library
./a.out
0.5

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./a.out
./a.out: error while loading shared libraries: libmy_math.so: cannot open shared object file: No such file or directory

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rm libmy_math.a 
./a.out
0.5