sizeof：运算符还是函数？
可能的重复：
为什么 sizeof 是一个运算符？
为什么 sizeof 应该是成为 C 语言中的运算符，&不是函数？
它的用法看起来与函数调用类似，如 sizeof(int) 中所示。
它应该是某种伪函数吗？
Possible Duplicate:
Why is sizeof an operator?
Why is sizeof supposed to be an operator in C, & not a function?
Its usage seems similar to that of a function call, as in sizeof(int).
Is it supposed to be some kind of a pseudo-function?
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因为它不是一个函数；不可能编写一个可以将类型作为参数并返回其大小的函数！另请注意，
sizeof是在编译时实现的，如果您在变量上使用它，则不需要括号。Because it's not a function; it's not possible to write a function that can take a type as an argument and return its size! Note also that
sizeofis implemented at compile-time, and that the parentheses aren't necessary if you're using it on a variable.函数调用是在运行时评估的。
sizeof必须在编译时求值（尽管我相信 C99 对此引入了一些例外）A function call is evaluated at runtime.
sizeofmust be evaluated at compile time (though C99 introduces some exceptions to this, I believe)C 中的函数无法执行 sizeof 需要执行的操作。
根据定义，函数在运行时分配空间，并且只能对数据进行操作。
虽然 sizeof 也对数据类型进行操作，但这些数据类型是特定于编译器的。根据设计，函数不知道如何解释数据类型“int”并询问编译器其大小。
在 C99 之前，sizeof 完全是编译时的，但在新标准中，它也可以用于在运行时获取可变长度数组的信息。
A function in C cannot do what sizeof needs to do.
A function by definition is allocated space at runtime and can operate on data only.
While sizeof operates on datatypes as well, which are compiler specific. A function does not know how to interpret the datatype "int" and ask the compiler for its size, by design.
Before C99 sizeof was totally compile-time, but in the new standard, it can be used to get information at runtime as well, for variable-length arrays.
函数是您可以在运行时调用的东西。 sizeof 只有编译器才能理解。
function is something you can call at runtime. sizeof is only understood by the compiler.
sizeof 在编译时而不是执行时产生影响。当您输入诸如 sizeof(int) 之类的类型时，您只需要 ( ) 但如果 'i' 是 int 类型，您可以执行 sizeof i
sizeof has its effects at complite time not execution time. You only need the ( ) when you enter a type such as sizeof(int) but if 'i' is of type int you could do sizeof i