path: root/tests/programs/defer.zc

namespace;
include rt;

// defer: code that runs when the enclosing block ends, on every way out of it

fn pn(x) { rt.put_n(x); rt.put_c(' '); return 0; }
fn nl() { rt.put_c(10); return 0; }

// several defers run in reverse order of registration
fn order() {
	pn(1);
	defer pn(30);
	defer pn(20);
	defer { pn(10); pn(11); }
	pn(2);
	return 0;
}

// the deferred code sees the values the variables have when it runs
fn late() {
	let x = 1;
	defer pn(x);
	x = 2;
	x = 7;
	return 0;
}

// the value of return is computed before the defers run
fn early(a) {
	let x = a;
	defer x = x + 100;
	defer pn(x);
	if (a > 5) return x * 2;
	x = x + 1;
	return x;
}

// a defer that is never reached registers nothing
fn skipped(a) {
	if (a == 0) return 0 - 1;
	defer pn(500);
	if (a == 1) return 1;
	defer pn(501);
	return 2;
}

// a defer inside an if only applies when that branch ran
fn branch(a) {
	defer pn(9);
	if (a) { defer pn(1); pn(2); }
	else { defer pn(3); pn(4); }
	pn(5);
	return 0;
}

// break and continue run the defers of the blocks they leave
fn loops() {
	let i = 0;
	defer pn(900);
	while (i < 5) {
		defer pn(100 + i);
		i++;
		if (i == 2) continue;
		if (i == 4) break;
		pn(i);
	}
	pn(777);
	for (let j = 0; j < 3; j++) {
		defer { pn(200 + j); }
		if (j == 1) { defer pn(300); continue; }
		pn(j);
	}
	let k = 0;
	do {
		k++;
		defer pn(400 + k);
		if (k == 2) continue;
		if (k == 3) break;
	} while (k < 10);
	return 0;
}

// the deferred code means what it meant where it was written: a variable an
// inner block declares again does not capture its names
fn lexical(a) {
	let x = 1;
	defer pn(x);
	{
		let x = 50;
		defer pn(x + 1);
		if (a) return x;
		pn(x);
	}
	x = 2;
	let y = 3;
	return y;
}

// a defer outside the loop is not run by break or continue
fn outer() {
	defer pn(1000);
	for (let i = 0; i < 3; i++) {
		defer pn(i);
		{
			defer pn(50 + i);
			if (i == 1) continue;
			pn(60 + i);
		}
		if (i == 2) break;
	}
	pn(2000);
	return 0;
}

// nested blocks, each with its own
fn nest() {
	defer pn(1);
	{
		defer pn(2);
		{
			defer pn(3);
			pn(4);
		}
		pn(5);
	}
	pn(6);
	return 7;
}

// switch arms are blocks; break leaves the arm and the arm's defers run
fn arms(v) {
	defer pn(0);
	switch (v) {
		case 1: defer pn(11); pn(10);
		case 2: defer pn(21); if (v == 2) break; pn(20);
		default: defer pn(31); return 30;
	}
	pn(99);
	return 0;
}

// a block expression is a block too
fn bexpr() {
	let v = { defer pn(1); pn(2); 40 + 2 };
	pn(v);
	return 0;
}

// the owner stays usable until the block ends; the defer is the transfer
fn owner(n) {
	let p = rt.new(4);
	defer rt.free(p);
	p[0] = n;
	p[1] = n * 2;
	if (n == 3) return p[0] + p[1];
	pn(p[0] + p[1]);
	return 0;
}

fn owner_loop() {
	for (let i = 0; i < 3; i++) {
		let p = rt.new(2);
		defer rt.free(p);
		p[0] = i;
		if (i == 1) continue;
		pn(p[0]);
	}
	return 0;
}

// defer in a closure belongs to the closure
fn closure_defer() {
	let f = fn(a) { defer pn(a + 1); pn(a); return a * 2; };
	defer pn(0);
	pn(f(10));
	return 0;
}

// unchecked code: no analysis, the deferred code still runs
unchecked fn fn_in() {
	defer pn(5);
	pn(4);
	if (1) return 0;
	return 1;
}
fn unchecked_defer() {
	unchecked {
		defer pn(3);
		pn(2);
	}
	fn_in();
	return 0;
}

// a deferred block can have its own loops, with break and continue
fn deferred_loop() {
	defer {
		for (let i = 0; i < 5; i++) {
			if (i == 1) continue;
			if (i == 4) break;
			pn(i);
		}
	}
	pn(9);
	return 0;
}

fn main() {
	order(); nl();
	late(); nl();
	pn(early(1)); nl();
	pn(early(9)); nl();
	pn(skipped(0)); nl();
	pn(skipped(1)); nl();
	pn(skipped(2)); nl();
	branch(1); nl();
	branch(0); nl();
	loops(); nl();
	outer(); nl();
	pn(lexical(1)); nl();
	pn(lexical(0)); nl();
	pn(nest()); nl();
	arms(1); nl();
	arms(2); nl();
	arms(3); nl();
	bexpr(); nl();
	let before = rt.live_objects();
	pn(owner(3)); owner(4); nl();
	owner_loop(); nl();
	pn(rt.live_objects() - before); nl();
	closure_defer(); nl();
	unchecked_defer(); nl();
	deferred_loop(); nl();
	return 0;
}