c - 重新类型转换一个变量，可能吗？

Question

是否可以永久地重铸 a 变量，或者有一个包装函数使变量的行为像另一种类型？

我想实现我在另一个问题中发布的内容: Typecasting variable with another typedef

更新:添加了 GCC 作为编译器。可能有一个有用的扩展？

Answer 1

是的，您可以将变量从一种类型转换为另一种类型:

 int x = 5;
 double y = (double) x; // <== this is what a cast looks like

但是，您不能就地修改标识符“x”的类型，如果这是您所要求的。不过，接近于此，您可以引入另一个作用域，该作用域使用某种新类型重新声明该标识符:

  int x = 5;
  double y = (double) x;
  {
      double x = y; // NOTE: this isn't the same as the 'x' identifier above
      // ...
  }
  // NOTE: the symbol 'x' reverts to its previous meaning here.

你可以做的另一件事是:

  int x = 5;
  double new_version_of_x = (double) x;  // Let's make 'x' mean this
  #define x new_version_of_x
  // The line above is pure evil, don't actually do it, but yes,
  // all lines after this one will think 'x' has type double instead
  // of int, because the text 'x' has been rewritten to refer to
  // 'new_version_of_x'. This will likely lead to all sorts of havoc