问题
There are some new integer types in the Windows API to support Win64. They haven't always been supported; e.g. they aren't present in MSVC6.
How can I write an #if condition to detect if these types are supported by <windows.h>?
(My code needs to compile under many different versions of Microsoft Visual C++, including MSVC6. So I need to provide my own definitions of these types, with an #if to disable them in newer compilers).
(For searchers, the full list of types is: DWORD_PTR, INT_PTR, LONG_PTR, UINT_PTR, ULONG_PTR)
回答1:
The macro MSC_VER is a value that is within the range [1200, 1300) for MSVC 6. So you can use #if MSC_VER>=1200 && MSC_VER<1300.
EDIT: As Anders said, this is not really that valid of a test beyond "is my compiler MSVC 6". However, you can also use:
#if defined(MAXULONG_PTR)
Since DWORD_PTR is a value type, it has a maximum value defined for it in basetsd.h.
回答2:
Since those types are typedefs there's not a great, reliable way to determine whether or not they're defined at the pre-processor stage. MSN's suggestion of testing the compiler version is pretty good, but as Anders indicated in a comment, a more recent SDK might be in use (I think VC6 was supported up through the 2003 SDK - I'm not sure if those types are in that SDK or not).
You could check for something the SDK does define as a macro that uses these types, like GetWindowLongPtr:
#if !defined( GetWindowLongPtr)
typedef DWORD DWORD_PTR;
#endif
Kludgy, but I think you might be stuck with kludgy.
来源：https://stackoverflow.com/questions/2723284/how-to-detect-if-the-windows-dword-ptr-type-is-supported-using-an-ifdef