用C typeof运算符 [英] typeof operator in C

问题描述

时的typeof在C，一个真正的运营商？结果
我想因为C中没有多态性，没有什么在运行时做的。也就是说，答案的typeof在编译时是已知的。 （我想不出一个使用typeof运算的，不会在编译时已知的。）所以这似乎更编译时指令，不是一个运营商。

Is typeof in C, really an operator?
I'm thinking because there is no polymorphism in C, that there is nothing to do at run-time. That is, the answer to typeof is known at compile-time. (I can't think of a use of typeof that would not be known at compile time.) So it appears to be more of a compile-time directive, than an operator.

typeof运算是否使用任何（处理器）运行时间（GCC）？

Does typeof use any (processor) run-time (in GCC)?

推荐答案

由于的typeof 是一个编译器扩展，没有真正为它的定义，但在传统的C这将是一个运营商，如：的sizeof 和 _Alignof 也被看作是一个运营商。

Since typeof is a compiler extension, there is not really a definition for it, but in the tradition of C it would be an operator, e.g sizeof and _Alignof are also seen as an operators.

和你错了，C具有动态类型只能在运行时确定：变量修改（VM）类型

And you are mistaken, C has dynamic types that are only determined at run time: variable modified (VM) types.

size_t n = strtoull(argv[1], 0, 0);
double A[n][n];
typeof(A) B;

只能在运行时确定。

can only be determined at run time.

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