The behaviour of GCC is by no means clearly defined. Even taking it as given that any memory handling errors will result in arbitrary code execution (accessing uninitialised memory as you say, but also e.g. double free), there are other cases. GCC has been known to compile the addition of two integers into an arbitrary code execution. It has been known to compile code like:

    void doDangerousStuffIfAuthorized(AUTHORIZATION* authorizationPtr){
      AUTHORIZATION authorization = *authorizationPtr
      if(authorizationPtr == null || !isValid(authorization)) return;
      doDangerousStuff();
    }

into something that executes doDangerousStuff() when passed null. When users complain about such things, the answer is that the code was causing undefined behaviour and so what GCC is doing is correct according to the standard.