#ifdef inside #define

I am trying to write something like this:

#define COV_ON(x) \
#ifdef COVERAGE_TOOL \
_Pragma (COVERAGE #x)
#endif

Is there any way to define `COV_ON` like this? I know what I have done above is wrong as I can't have `#ifdef` inside #define. (`#` is not an allowed character in `#define`).
So is there any solution?

Simply turn it around:

#ifdef COVERAGE_TOOL
#define COV_ON(x) _Pragma (COVERAGE #x)
#else
#define COV_ON(x) /* foo */
#endif

#ifdef COVERAGE_TOOL
#define COV_ON(x) _Pragma (COVERAGE #x)
#else
#define COV_ON(x)
#endif

You cannot. But you can swap `#ifdef` and `#define`:

#ifdef COVERAGE_TOOL
# define COV_ON(x) _Pragma (COVERAGE #x)
#else
# define COV_ON(x)
#endif

Not possible. Do it the other way around:

#ifdef COVERAGE_TOOL
#define COV_ON(x) _Pragma (COVERAGE #x)
#else
#define COV_ON(x)
#endif

As you mentioned it is not possible to have an #ifdef in a #define. What you should do instead is reverse the order:

#ifdef COVERAGE_TOOL \
#define COV_ON(x) \
etc.
#endif