Question

Can anyone tell me what this C statement means?

 static uint8_t chess_storage(DM%2) host_response[14] ;

Answer 1

It’s not valid C, you can’t have a % in that location. And you also can’t have that entire chess_storage(DM%2) thing in there, unless (possibly) it’s a macro that does something that you can do.

This:

static uint8_t host_response[14];

would declare host_response as an array of 14 8-bit unsigned integers (aka “bytes”).

If we add this:

#define chess_storage(size)
#define DM 1

then the code becomes at least valid, substituting we get a call of the macro chess_storage with the argument 1%2, which the preprocessor is able to compute. Since the macro is empty, that whole term will just go away, leaving the above array declaration.

There are probably other more “artistic” macros possible, too.