I'm inexperienced with C, and working on a microcontroller with messages stored in arrays where each byte does something different. How do I give each element of the array a human-readable name instead of referencing them as msg[1], msg[2], etc.?
Is this what structs are for? But "you cannot make assumptions about the binary layout of a structure, as it may have padding between fields."
Should I just use macros like this? (I know "macros are bad", but the code is already full of them)
#define MSG_ID msg[0]
#define MSG_COMMAND msg[1]
Oh! Or I guess I could just do
MSG_ID = 0;
MSG_COMMAND = 1;
MSG[MSG_ID];
That's probably better, if a little uglier.
If you want to go that route, use a macro, for sure, but make them better than what you suggest:
Which will allow the code to name the arrays in ways that make sense, instead of ways that work with the macro.
Otherwise, you can define constants for the indexes instead (sorry I could not come up with better names for them...):
And macros are not bad if they are used responsibly. This kind of "simple aliasing" is one of the cases where macros help making the code easier to read and understand, provided the macros are named appropriately and well documented.
Edit: per @Lundin's comments, the best way to improve readability and safety of the code is to introduce a type and a set of functions, like so (assuming you store in
char
and a message isMESSAGE_SIZE
long):This method, though it brings some level of type safety and allows you to abstract the storage away from the use, also introduces call overhead, which in microcontroller world might be problematic. The compiler may alleviate some of this through inlining the functions (which you could incentize by adding the
inline
keyword to the definitions).