Is it possible to have one macro expanded differently for one specific argument value and differently for all other arguments?
Say I define a current user:
#define CURRENT_USER john_smith
What I want to be able to do is to have a macro that will be expanded differently if user passed matches CURRENT_USER. Mind you that I don't know all possible user a priori. The most basic case:
#define IS_CURRENT_USER(user) \
/* this is not valid preprocessor macro */ \
#if user == CURRENT_USER \
1 \
#else \
0 \
#endif
With macro like that every other macro relying on the username could be done following way:
#define SOME_USER_SPECIFIC_MACRO(user) SOME_USER_SPECIFIC_MACRO_SWITCH_1(IS_CURRENT_USER(user))
#define SOME_USER_SPECIFIC_MACRO_SWITCH_1(switch) SOME_USER_SPECIFIC_MACRO_SWITCH_2(switch) // expand switch ...
#define SOME_USER_SPECIFIC_MACRO_SWITCH_2(switch) SOME_USER_SPECIFIC_MACRO_##switch // ... and select specific case
#define SOME_USER_SPECIFIC_MACRO_0 ... // not current user
#define SOME_USER_SPECIFIC_MACRO_1 ... // current user
Is this possible?
EDIT: Let me clarify. Say each programmer defines different CURRENT_USER in their config header. I want user specific macros to exand to something meaningful if and only if their user argument matches CURRENT_USER. As I would like those macros to contain _pragmas it can't be runtime check (as proposed in some anwsers below).
EDIT: Again, clarification. Say there's macro to disable optimisation of some sections of code:
#define TURN_OPTIMISATION_OFF __pragma optimize("", off)
Some programmers want to turn optimisation off for different sections of code but not all at one time. What I'd like is to have a macro:
#define TURN_OPTIMISATION_OFF(user) /* magic */
That will match user argument against CURRENT_USER macro, taken from per-programmer config file. If the user matches macro is expanded into pragma. If not, to nothing.