c++ - 为什么 catch block 不共享 try block 的范围？

Question

令人惊讶的是，我无法通过谷歌搜索和搜索 SO 找到答案(关于 SO 有很多类似的问题，但与其他语言相关)。

我怀疑答案是否。如果是这样，就会有明显的不便，例如

try
{
  std::string fname = constructFileName(); // can throw MyException
  ofstream f;
  f.exceptions(ofstream::failbit | ofstream::badbit);
  f.open(fname.c_str());
  // ...
}
catch (ofstream::failure &e)
{
  cout << "opening file " << fname << " failed\n"; // fname is not in the scope
}
catch (MyException &e)
{
  cout << "constructing file name failed\n";
}

如果我的假设是正确的，你会如何处理？通过将 std::string fname; 移出 try，我猜？

我知道范围是由 {} block 定义的，但这似乎是一个合理的情况，嗯，异常(exception)。是不是抛出异常导致对象不能完全构造的原因？

Answer 1

Does catch block share the scope of the try block?

没有。

How do you deal with this? By moving the std::string fname; out of try, I guess?

是的。

I understand that a scope is defined by a {} block, but this seems as a reasonable case for, hmm, exception. Is the reason for that that objects can be not fully constructed if an exception is thrown?

C++ 最不需要的就是更复杂的规则和规则异常(exception)。 :-)