nmatthews-witekio
commented
10 months ago Clarification:
Think of a debug routine like printf...
one_bracket_debug("This is the value %d", x); then the one_bracket_debug macro has 2 arguments -- "This is the value %d" and x This means you have to use __va_args__ to deal with the extra multiple optional arguments.
if you use the double-bracket technique then: two_bracket_debug(("This is the value %d", x)); then the two_bracket_debug macro has 1 argument -- ("This is the value %d", x) So it can work without needing __va_args__i.e. on an older compiler.
Also if you do:
define two_bracket_debug(x)
the compiler knows that the argument x is unused -- so it can throw away all of -- ("This is the value %d", x) so the string literal "This is the value %d" probably doesn't make it into the executable
You could use __va_args__:
define one_bracket_debug(x...)
but there's probably a bit less chance for the compiler to be able to discard the string "This is the value %d"
That's all. It looks a bit weird in the code -- but actually it sort of makes sense -- especially if you do
define two_bracket_debug(x) printf x
then the single argument -- ("This is the value %d", x) -- gets rewritten easily as printf ("This is the value %d", x)
Add debugging routines
Macro definition with (()) allows all debugging strings to be removed from the executable if required -- keeping executable size smaller -- but allowing debugging to be turned on if/when required.