Avoiding #if defined (xxx) typos

[akevan]

I'm wondering how to avoid typos in #ifdef pre-processor directives.

Obviously if I type #ifdef OPTIMIZED, and OPTIMIZED is spelled incorrectly, it will default to NOT optimized. Is there any way to avoid this and get the compiler to throw an error?

I remember seeing some code that looked like:

#define CORE_ON  1
#define CORE_OFF 0
#if (SOME_DIRECTIVE == CORE_OFF)
...
#endif
 

But that still seems vulnerable to typo errors... any tricks you guys have used to avoid this?

[Banfa]

Well this is unlikely to be an error that you miss, a missed type preprocessor symbol is like to cause altered program behaviour that should so up in testing if it doesn't cause an outright compiler error.

However you can take advantage of the fact that an undefined symbol is given the numeric value 0 by the preprocessor to do something like

#define OPTION1 1
#define OPTION2 2
#define OPTION3 3
 
#define SELECTED_OPTION OPTION3
 
#if (SELECTED_OPTION == OPTION1)
// option 1 code
#elif (SELECTED_OPTION == OPTION2)
// option 2 code
#if (SELECTED_OPTION == OPTION3)
// option 3 code
#else
#error SELECTED_OPTION Invalid
#endif
 

Note that your code doesn't do this because it defines CORE_OFF to 0 so you would not be able to tell the difference between CORE_OFF and any undefined symbol.