[Runtime macro] Where can I find those stuffs?

Wed Feb 25 18:57:00 GMT 2004

Alvyn Liang wrote:
> I also find out there are so many macros such as __i486__, __i586__,
> _M_IX86, _X86_, WIN32_LEAN_AND_MEAN, __USE_W32_SOCKETS... , etc. They are
> not in the textbooks I bought. I bought "GCC The complete Reference" and
> some c++ books, they do not mention so many variables. Can someone tell me
> where I can find the information of those Macros?

That's a long story, now..
* Some macros are built in to GCC (__i486__, etc.)
* Some macros are required by the platform header files for enabling or 
disabling certain bits of functionality (e.g. WIN32_LEAN_AND_MEAN, etc.) 
For these, the rule is that you use them if the platform documentation 
tells you to use them. (I.e. *RTFM* first!)
There's a nice way to tell you what the "standard GCC macros" for a 
platform are:
 % touch xx.c # empty file
 % gcc -dN -E xx.c # or -dM
This will dump out a nice dump of all the macros that are compiled in to 
cc1, or are passed in from the spec file. -dN will print only the 
names, while -dM will print the full #define statements.
Really useful..
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