Escaping a # symbol in a #define macro?

Question

Without going into the gory details I want to use a #define macro that will expand to a #include but the '#' sign is confusing the preprocessor (as it thinks I want to quote an argument.)

For example, I want to do something like this:

#define MACRO(name) #include "name##foo" 

And use it thus:

MACRO(Test) 

Which will expand to:

#include "Testfoo" 

The humble # sign is causing the preprocessor to barf. MinGW gives me the following error:

'#' is not followed by a macro parameter

I guess I need to escape the # sign but I don't if this is even possible.

Yes, macros are indeed evil...

Answer 1

It is possible to insert a hash token into the preprocessed token stream. You can do it as follows:

#define MACRO(hash, name) hash include name MACRO(#,"hello") 

—expands to:

# include "hello" 

However, the standard explicitly rules out any further analysis of such line for the existence of preprocessing directives [cpp.rescan]:

The resulting completely macro-replaced preprocessing token sequence is not processed as a preprocessing directive even if it resembles one.

Answer 2

As far as I remember you cannot use another preprocessor directive in define.