#if and #error directive

future · Joined: 14 May 2004 Posts: 330

Hello,

I am trying to achieve something like this:

#if (sizeof(cfg)+sizeof(dia))>255 // if size of those 2 structs is greater than 255
#error eeprom full! // show the error
#endif

I get "expression must evaluate to a constant".

Does anyone know another way?

Thank you.

RossJ · Joined: 25 Aug 2004 Posts: 66

Your code works for me (compiled with PCWH 3.214 for a PIC18F2620). Are you sure cfg and dia are types and not just variables. You can't sizeof a variable, just its type. If you are creating structs, then you must use the typedef operator to declare a new type. Then do your sizeof with the type and declare your variables of the type. Also, make sure you have declared your types BEFORE trying to do a sizeof on it.