excDblThrow.cc

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// Explore single- and double-throwing techniques
 
 
#include <iostream>
  using std::cerr;
 
 
struct B  {
 
  B()                         { cerr << "make B\n"; }
  B( B const & b )            { cerr << "copy B\n"; }
  virtual char  type() const  { return 'B'; };
 
};  // struct B
 
 
struct D : public B  {
 
  D()                         { cerr << "make D\n"; }
  D( const D & d ) : B( d )   { cerr << "copy D\n"; }
  virtual char  type() const  { return 'D'; };
 
};  // struct D
 
 
#define single( obj )               \
  cerr << "\nsingle( " #obj " )\n"; \
  const B &  ref = obj;             \
  throw ref;
 
 
#define double( obj )               \
  cerr << "\ndouble( " #obj " )\n"; \
  try  { throw obj; }               \
  catch ( const B & x )  { throw; }
 
 
void  f( void g() )  {
 
  try  { g(); }
//catch( D const & x )  { cerr << "Caught D is " << x.type() << '\n'; }
  catch( B const & x )  { cerr << "Caught B is " << x.type() << '\n'; }
 
}
 
 
void  test1()  { double( B() ); }
void  test2()  { double( D() ); }
void  test3()  { single( B() ); }
void  test4()  { single( D() ); }
 
 
int  main()  {
 
  cerr << "\nTesting double throws:\n";
  f( test1 );
  f( test2 );
 
  cerr << "\nTesting single throws:\n";
  f( test3 );
  f( test4 );
 
}