Is there a way to escape a C preprocessor directive?

Question

What I am trying to do is have the C preprocessor output #ifdef, #else, and #endif directives. That is, I would like to somehow "escape" a directive so that the output of the preprocessor includes the directive were the preprocessor to run on the output.

Is it possible to "escape" a CPP directive so that it is outputted by the preprocessor such that the output of an escaped directive would be a preprocessor directive if the CPP output were to be itself preprocessed?

Answer 1

A slight variant of Marcelo Cantos's answer works for me on GNU cpp 4.4.3:

#define HASH(x) x

...

HASH(#)ifdef __cplusplus
class foo { };
HASH(#)endif