关于ARRAYSIZE宏的问题

Question

我在MSDN.TextOut函数说明档中看到了一个ARRAYSIZE宏.(http://msdn.microsoft.com/en-us/library/dd145133(VS.85).aspx)
然后google发现有人讲该宏位于winnt.h中.(http://blog.csdn.net/zengkun100/archive/2008/12/21/3573575.aspx)
但是我并没有在我的visual studio 6(en)中的VC/INCLUDE/WINNT.H中发现该宏.

请问诸君,该宏是否存在,存在于何种版本当中?

MichealY

Answer 1

需要Visual C++ 2005或者更高版本

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MSMVP VC++

Answer 2

// RtlpNumberOf is a function that takes a reference to an array of N Ts.
//
// typedef T array_of_T[N];
// typedef array_of_T &reference_to_array_of_T;
//
// RtlpNumberOf returns a pointer to an array of N chars.
// We could return a reference instead of a pointer but older compilers do not accept that.
//
// typedef char array_of_char[N];
// typedef array_of_char *pointer_to_array_of_char;
//
// sizeof(array_of_char) == N
// sizeof(*pointer_to_array_of_char) == N
//
// pointer_to_array_of_char RtlpNumberOf(reference_to_array_of_T);
//
// We never even call RtlpNumberOf, we just take the size of dereferencing its return type.
// We do not even implement RtlpNumberOf, we just decare it.
//
// Attempts to pass pointers instead of arrays to this macro result in compile time errors.
// That is the point.
//
extern "C++" // templates cannot be declared to have 'C' linkage
template <typename T, size_t N>
char (*RtlpNumberOf( UNALIGNED T (&)[N] ))[N];

#define RTL_NUMBER_OF_V2(A) (sizeof(*RtlpNumberOf(A)))

#define ARRAYSIZE(A)    RTL_NUMBER_OF_V2(A)

这个宏是调用RtlpNumberOf 的,RTL开头的一般都是内核函数.

还有一种定义方法,这种方法也是可以获得数组长度的.
#define ARRAYSIZE(A) (sizeof(A)/sizeof((A)[0]))

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Hello world