问题
I am trying to include 2 platform-specific stdafx.h files in my .cpp file, but the compiler is unhappy when I try to #ifdef it.
#ifdef _WIN32
#include "stdafx.h"
#elif _MAC
#include "MAC/stdafx.h"
#endif
You may wonder why I am using stdafx.h in the Mac code, but that is not important at the moment :).
When I try to compile the code on Windows, I receive: Fatal Error C1018. I tried enclosing other header files with #ifdef in the same file, and the compiler was happy. Therefore, it looks like Windows doesn't like stdafx.h to be #ifdef-ed, or that Windows only allows #include stdafx.h to be the first line in the file.
So my question is, why?
Kat
回答1:
When the compiler includes a pre-compiled header, it basically "forgets" anything that came before the header. Thus your #elif isn't matched to a #if anymore.
回答2:
This is because you have Precompiled Headers turned on - turn it off and you should be fine.
来源：https://stackoverflow.com/questions/1435804/why-am-i-unable-to-ifdef-stdafx-h