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Variables defined by if-cases leak? (aka why is this even compiling?)

Do the variables declared inside the if statement seem to leak to the following expression?

I copied, copied some code and, to my surprise, it compiled when it shouldn't have been! I was going to pass the code, and I guessed that I had reached an error before that. Below is a working (?) Program that shows the problem.

The following code fragment calls a function for an object that does not exist:

#include <iostream>

class A {
public:
  virtual ~A() {}
};

class B : public A {
public:
  void fooB() { std::cout << "fooB\n"; }
};

class C : public A {
public:
  void fooC() { std::cout << "fooC\n"; }
};

int main() {

   A* a = new C();

   if (B* b = dynamic_cast<B*>(a)) {
      b->fooB();
   } else if (C* c = dynamic_cast<C*>(a)) {
      c->fooC();
      b->fooB();
   }

   return 0;
}

It compiles, and the output is this way:

fooC
fooB

This, of course, is wrong. Should I include some warnings to prevent this code from compiling?

Imagine the horrors if I tried to access some member variables or call a virtual function!

Same behavior in both VS2008 and GCC 4.8

+4
1

, b NULL else, - undefined.

+6

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