How to generate random variable names in C++ using macros?

Question

I\'m creating a macro in C++ that declares a variable and assigns some value to it. Depending on how the macro is used, the second occurrence of the macro can override the v

Answer 1

Try the following:

// This is some crazy magic that helps produce __BASE__247
// Vanilla interpolation of __BASE__##__LINE__ would produce __BASE____LINE__
// I still can't figure out why it works, but it has to do with macro resolution ordering
#define PP_CAT(a, b) PP_CAT_I(a, b)
#define PP_CAT_I(a, b) PP_CAT_II(~, a ## b)
#define PP_CAT_II(p, res) res

#define UNIQUE_NAME(base) PP_CAT(base, __COUNTER__)

__COUNTER__ is rumored to have portability issues. If so, you can use __LINE__ instead and as long as you aren't calling the macro more than once per line or sharing the names across compilation units, you will be just fine.

Answer 2

Instead of having the preprocesser create a name, you could possibly let the macro user give you a name.

#define MY_MACRO(varname) int varname = getCurrentTime();