intercept.cc

#include <stdio.h>

#define NARG(...)  NARG_(__VA_ARGS__, RSEQ_N())
#define NARG_(...) ARG_N(__VA_ARGS__)
#define RSEQ_N() 8, 7, 6, 5, 4, 3, 2, 1, 0
#define ARG_N(_1, _2, _3, _4, _5, _6, _7, _8,  N, ...) N
#define CONCAT_(x, y) x##y
#define CONCAT(x, y) CONCAT_( x, y )
#define OVERLOAD(X, ...) CONCAT(X, NARG(__VA_ARGS__))
#define INTERCEPT(ret, func, ...) OVERLOAD(INTER, __VA_ARGS__)(ret, func, __VA_ARGS__)
#define INTER1(ret, func, unused) ret func() { return _##func(); }
#define INTER2(ret, func, t0, a0) ret func(t0 a0) { return _##func(a0); }
#define INTER4(ret, func, t0, a0, t1, a1) ret func(t0 a0, t1 a1) { return _##func(a0, a1); }

void _bar() {
	printf("_bar()\n");
}

int _foo(int x) {
	printf("_foo(%d)\n", x);
	return 0;
}

int _baz(int x, const char* s) {
	printf("_baz(%d, %s)\n", x, s);
	return 0;
}

INTERCEPT(void, bar);
INTERCEPT(int, foo, int, x);
INTERCEPT(int, baz, int, x, const char*, s);

int main() {
	bar();
	foo(1);
	baz(2, "hello");
}