Request for information on the __INSIDE_CYGWIN__ #define

[Sean Seefried]

Hi guys,

I'm not entirely sure this is the place to ask this question. This  
question may be better directed towards the GCC mailing list. However,  
I hope someone here can help me.

My question centers around the __INSIDE_CYGWIN__ #define. From what I  
can gather from looking through the header files in /usr/include and  
sub-directories, it is used to "protect" Cygwin users from seeing  
Microsoft extensions in their preprocessed output. (It often prevents  
__declspec declarations from being defined for instance.)

However, try as I might, I simply cannot find a single place where it  
is defined.  So my natural thought is that one of the tools in the GNU  
Compiler Collection defines it. However, passing the verbose (-v)  
option showed that only __CYGWIN__ and __CYGWIN32__ were defined.

My questions are manifold:

a) How does this symbol get #defined?
b) If it's from some tool can someone provide me with command line  
flags to that tool which will show me all the other #defines it does?  
Or perhaps the information is in a configuration file somewhere. If  
so, could someone tell me where that is?
c) Why isn't this documented somewhere? I tried googling the symbol  
and got a mere three entries on it. Normally I wouldn't bother a high- 
volume list with what seems like such a basic question, but I simply  
couldn't find any other information on it.

If this is indeed the wrong place to ask this question could someone  
point me to the appropriate place? It'd be much appreciated.

Cheers,

Sean

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