Re: [boost] Preprocessot question

From: Paul Mensonides (pmenso57_at_[hidden])
Date: 2005-08-30 03:41:58

> -----Original Message-----
> From: boost-bounces_at_[hidden] 
> [mailto:boost-bounces_at_[hidden]] On Behalf Of Suman Cherukuri

> I'm using general 'C' compiler in this project (hence I 
> cannot use boost headers).  I want to write a macro as follows;
> 
> #define ERR(x, y) \
> { \
> #	ifndef ERR##x \
> #	define ERR##x \
> #	else \
> #	error ERR##x already defined\
> #	endif
> 	y = x; \
> }

As mentioned by Graeme, macros cannot expand to preprocessing directives.  Or,
more precisely, they cannot expand to anything that will be _interpreted_ as
preprocessing directives.  In the above, because it is a function-like macro,
the # token acts as a stringizing operator.  However, applying the stringizing
operator to anything but a formal argument is ill-formed.

Regards,
Paul Mensonides