Added declaration for LMIC_DEBUG_PRINTF_FN

[frankleonrose]

Fix to #39.

[terrillmoore]

Hi Frank, I agree that we should do something like this.

The (undocumented) design intention was that the definition of LMIC_DEBUG_PRINTF_FN, if used, would come from the file pointed to by LMIC_DEBUG_INCLUDE; and so that file would also provide the prototype. I did not want to require that LMIC_DEBUG_PRINTF_FN be the name of a function, and I didn't want to dictate the prototype.

Other code is already using LMIC_DEBUG_PRINTF_FN with LMIC_DEBUG_INCLUDE, and so is already providing a prototype. I'm a little worried about providing the prototype in this way.

We could reliably detect a "command-line definition" (your use case) by checking a few thing before we include LMIC_DEBUG_INCLUDE. We'd have something like this:

#if LMIC_DEBUG_LEVEL > 0
# if defined(LMIC_DEBUG_PRINTF_FN) && ! defined(LMIC_DEBUG_INCLUDE)
//
// If defined at this point, LMIC_DEBUG_PRINTF_FN came from the build system.
// We don't have  LMIC_DEBUG_INCLUDE, so we need a prototype..
//
void LMIC_DEBUG_PRINTF_FN(const char *fmt, ...);
# endif

# ifdef LMIC_DEBUG_INCLUDE
// ... current code
# endif

# ifndef LMIC_DEBUG_PRINTF
// ... code as at present.

What do you think? I think this would be less intrusive. [Equivalently, and possibly less confusingly, we could do:

# ifdef LMIC_DEBUG_INCLUDE
...
# else if defined(LMIC_DEBUG_PRINTF_FN)
void LMIC_DEBUG_PRITNF_FN(const char *, ...);
# endif

(I now kind of like the second way better.)
--Terry

[frankleonrose]

How about just wrapping the declaration in #ifndef LMIC_DEBUG_INCLUDE?

#     ifndef LMIC_DEBUG_INCLUDE // If you use LMIC_DEBUG_INCLUDE, put the declaration in there
        void LMIC_DEBUG_PRINTF_FN(const char *f, ...);
#     endif // ndef LMIC_DEBUG_INCLUDE

Your second way would require repetition of the #define LMIC_DEBUG_PRINTF line and doesn't seem more clear.

#if defined(LMIC_DEBUG_INCLUDE)
...stringify...include...
# if !defined(LMIC_DEBUG_PRINTF)
#   ifdef LMIC_DEBUG_PRINTF_FN
#     define LMIC_DEBUG_PRINTF(f, ...) LMIC_DEBUG_PRINTF_FN(f, ## __VA_ARGS__) <-- same
#   else // ndef LMIC_DEBUG_PRINTF_FN
#     define LMIC_DEBUG_PRINTF(f, ...) printf(f, ## __VA_ARGS__)
#   endif // ndef LMIC_DEBUG_PRINTF_FN
# endif
#elif !defined(LMIC_DEBUG_PRINTF) && defined(LMIC_DEBUG_PRINTF_FN)
#     define LMIC_DEBUG_PRINTF(f, ...) LMIC_DEBUG_PRINTF_FN(f, ## __VA_ARGS__) <-- same
        void LMIC_DEBUG_PRINTF_FN(const char *f, ...);
# endif

[terrillmoore]

How about just wrapping the declaration in #ifndef LMIC_DEBUG_INCLUDE?

Agreed, much better. Will you push a change in that format or shall I?

[frankleonrose]

Done.