> Here, there's a conflict between the lexical scope of the function (main) and the macro (SWAP). It might interest to some to know that GCC has a macro called

> Here, there's a conflict between the lexical scope of the function (main) and the macro (SWAP). It might interest to some to know that GCC has a macro called __COUNTER__ (apparently also implemented by clang and MS), which auto-increments its value. You can then create something like a gensym to avoid conflict. Here's an implementation of the "defer" keyword in C++: template <typename F> struct privDefer { F f; privDefer(F f) : f(f) {} ~privDefer() { f(); } }; template <typename F> privDefer<F> defer_func(F f) { return privDefer<F>(f); } #define DEFER_1(x, y) x##y #define DEFER_2(x, y) DEFER_1(x, y) #define DEFER_3(x) DEFER_2(x, __COUNTER__) #define defer(code) auto DEFER_3(_defer_) = defer_func([&](){code;}) It was written by gingerBill, author of the Odin programming language.