头文件被包含的顺序？
头文件被包含的顺序？
想定义一个宏，然后根据这个宏是否被定义来个条件编译，问题来了：怎么保证编译这个条件编译的时候，定义宏的头文件一定被包含了呢？ 如果在定义这个宏的头文件之前使用了条件编译，就达不到想要的效果了。
所以，这个宏应该定义在哪个头文件里呢？工程里文件很多的话，怎么确定这样的宏应该写在哪里？
[解决办法]
不想在头文件里定义，那就 ，工程->项目属性->通用配置->C/C++ ->预处理器->预处理器定义，
把你的宏仍在那里就行。
[解决办法]
CoCreateGuid
Creates a GUID, a unique 128-bit integer used for CLSIDs and interface identifiers.
HRESULT CoCreateGuid(
GUID *pguid //Pointer to the GUID on return
);
Parameter
pguid
[out] Pointer to the requested GUID on return.
Return Value
S_OK
The GUID was successfully created.
Win32 errors are returned byUuidCreate but wrapped as an HRESULT.
Remarks
The CoCreateGuid function calls the RPC function UuidCreate, which creates a GUID, a globally unique 128-bit integer. Use the CoCreateGuid function when you need an absolutely unique number that you will use as a persistent identifier in a distributed environment.To a very high degree of certainty, this function returns a unique value – no other invocation, on the same or any other system (networked or not), should return the same value.
[解决办法]
