Conditional value for a #define

问题

I want to define a macro kDependentMacro to be 38 if the macro kIndependentMacro is defined and 40 otherwise. What is the simplest way to do that?

回答1:

#ifdef kIndependentMacro
#  define kDependentMacro 38
#else
#  define kDependentMacro 40
#endif

来源：https://stackoverflow.com/questions/3041300/conditional-value-for-a-define