使用dynamic_cast转换问题！
帮忙看看是什么问题：

C/C++ code

#include <iostream>#include <fstream>#include <string>using namespace std;void write(ostream &file){     ofstream &file1=dynamic_cast<ofstream&>(file);     file1.put('a');}int main(){    string  filename;    cin>>filename;    ofstream ifile;    ifile.open(filename.c_str(),ofstream::app);    write(ifile);      ifile.close();    ifile.clear();    return 0; }

[解决办法]
当然不对了
dynamic_cast是向上转化的，你这是向下转换，不安全
[解决办法]
MSDN
class B { ... };
class D : public B { ... };

void f()
{
B* pb = new D; // unclear but ok
B* pb2 = new B;

D* pd = dynamic_cast<D*>(pb); // ok: pb actually points to a D
...
D* pd2 = dynamic_cast<D*>(pb2); //error: pb2 points to a B, not a D
// pd2 == NULL
...
}