Multiple preprocessor directives on one line in C++

Question

A hypothetical question: Is it possible to have a C++ program, which includes preprocessor directives, entirely on one line?

Such a line would look like this:

Answer 1

A few years late - but here is a pattern I use every day:

#ifdef _DEBUG
    #define DEBUGTRACE(debuglevel, code)    \
        if ( traceLevelActive(debuglevel) ) \
            {code}
#else
    #define DEBUGTRACE(debuglevel, code)
#endif

Usage:

DEBUGTRACE(DEBUG_LEVEL2, printf("you are in debug mode"); );

or, more elaborate:

DEBUGTRACE(DEBUG_LEVEL2, {
    if (somethingistrue)
        printf("Debugging is TRUE");
    else
        foo();
});

If _DEBUG is defined, then your code is include. If not, then nothing is not compiled.