apply() Demo

demo.c

#include <stdio.h>

extern void* apply(void* func, void** args, size_t argc);

long bar(int a, int b, long c, long d, int e, long f, long g, int h) {
	printf( "a = %x\n"
		"b = %x\n"
		"c = %lx\n"
		"d = %lx\n"
		"e = %x\n"
		"f = %lx\n"
		"g = %lx\n"
		"h = %x\n",
		a, b, c, d, e, f, g, h);
	return h;
}

long foo(long a, long b, long c) {
	long baz = a ^ b & c;
	printf("a ^ b & c = %d\n", baz);

	long args[] = {
		0xaaddaadd,
		0xddaaddaa,
		0xaaaaaaaabbbbbbbb,
		0x1234123412341234,
		1,
		0x4321432143214321,
		0x9879879879879879,
		2
	};
	void* result = apply(bar, (void**) &args, 8);
	printf("--> %ld\n", (long) result);
	return (long) result;
}

int main() {
	long args[] = {3, 4, 5};
	void* result = apply(foo, (void**) &args, 3);
	printf("-> %ld\n", (long) result);
	return 0;
}

/*
$ ./test
	a ^ b & c = 7
	a = aaddaadd
	b = ddaaddaa
	c = aaaaaaaabbbbbbbb
	d = 1234123412341234
	e = 1
	f = 4321432143214321
	g = 9879879879879879
	h = 2
	--> 2
	-> 2
*/

What about arguments of different types?

This implementation doesn't handle types larger than 8 bytes. You might be interested in libapply (https://github.com/davvid/libapply), which is a much more general implementation.