Re: #define in a macro definition

[bill <bill dot pursell at gmail dot com>]

Brian Dessent wrote:

> "Samuel J. Guido" wrote:
>
>  
>
> > Is it possible with GCC to define an object-like macro within a
> > function-like macro, i.e. this is what I am trying to do...
> >
> > #define MyMacro(a) \
> >    #define a##Type 55
> >    
>
> As far as I can tell ISO C99 forbids this, in §6.10.3.2.1 which says:
>
> "Each # preprocessing token in the replacement list for a function-like
> macro shall be followed by a parameter as the next preprocessing token
> in the replacement list."
>
> So "#define" in the replacement list would be illegal unless 'define'
> was a parameter, in which case it would stringify it.
>
> I don't think what you're trying to do is possible in general with gcc,
> but I could be wrong.  Maybe if you explain in more detail why you would
> need such a thing, someone would be able to offer an alternative.
>
> Brian
>
>  
I was trying to do exactly this type of thing just last night!  My 
reason is I've got
a bunch of code that reads:
#ifdef FOO
debug("FOO\n");
#endif
It's printing to a debug file to help track down what options were 
defined.  This is
several hundred lines of code, and it's a bit ugly.  It would be nice to 
be able to 
write "PRINT_MACRO(FOO)"  and have it expand to the 3 lines above.