builtin: fix map.clear() not resetting map's metas and keys blocks (fix #22139) (#22140)

cmd/tools/bench/map_clear.v

@@ -0,0 +1,19 @@
+import benchmark
+
+fn main() {
+	max_iterations := arguments()[1] or { '1_000_000' }.int()
+	assert max_iterations > 0
+	mut m := {
+		123: 456
+		789: 321
+	}
+	mut volatile sum := u64(0)
+	mut b := benchmark.start()
+	for i in 0 .. max_iterations {
+		m.clear()
+		m[i] = i * 2
+		sum += u64(m.len)
+	}
+	assert m.len == 1
+	b.measure('m.clear(), iterations: ${max_iterations}, sum: ${sum}')
+}

cmd/tools/bench/map_clear_runner.vsh

@@ -0,0 +1,23 @@
+#!/usr/bin/env -S v -raw-vsh-tmp-prefix tmp
+
+import os
+
+const time_fmt = '"CPU: %Us\tReal: %es\tElapsed: %E\tRAM: %MKB\t%C"'
+const flags = os.getenv('FLAGS')
+
+unbuffer_stdout()
+
+start := os.args[1] or { '1_000_000' }.int()
+end := os.args[2] or { '10_000_000' }.int()
+step := os.args[3] or { '500_000' }.int()
+
+os.chdir(os.dir(@VEXE))!
+vcmd := 'v ${flags} cmd/tools/bench/map_clear.v'
+
+println('>> start: ${start} | end: ${end} | step: ${step} | workdir: "${os.getwd()}" | flags: "${flags}" | vcmd: "${vcmd}"')
+assert os.system(vcmd) == 0
+
+println('running...')
+for i := start; i <= end; i += step {
+	os.system('/usr/bin/time -f ${time_fmt} cmd/tools/bench/map_clear ${i}') == 0
+}

vlib/builtin/map.v

@@ -317,6 +317,14 @@ pub fn (mut m map) clear() {
 	m.len = 0
 	m.even_index = 0
 	m.key_values.len = 0
+	m.key_values.deletes = 0
+	unsafe {
+		if m.key_values.all_deleted != 0 {
+			free(m.key_values.all_deleted)
+		}
+		vmemset(m.key_values.keys, 0, m.key_values.key_bytes * m.key_values.cap)
+		vmemset(m.metas, 0, sizeof(u32) * (m.even_index + 2 + m.extra_metas))
+	}
 }
 
 @[inline]

vlib/builtin/map_issue_22139_clear_test.v

@@ -0,0 +1,59 @@
+fn test_map_clear_done_several_times() {
+	mut ints := map[int]int{}
+
+	ints[5] = 5
+	dump(ints.len)
+	assert ints.len == 1
+
+	ints.clear()
+	dump(ints.len)
+	assert ints.len == 0
+
+	ints[5] = 3
+	dump(ints.len)
+	assert ints.len == 1
+
+	ints.clear()
+	dump(ints.len)
+	assert ints.len == 0
+
+	ints[5] = 123
+	dump(ints.len)
+	assert ints.len == 1
+}
+
+fn test_map_clear_in_loop_metas_should_be_cleared_too() {
+	mut ints := map[int]int{}
+	for i in 0 .. 100 {
+		ints[i] = i * 123
+		ints.clear()
+		assert ints.len == 0
+		// dump(ints)
+		ints[i] = i
+		// dump(ints)
+		assert ints.len == 1
+		ints[1000 + i] = 1000 * i
+		assert ints.len == 2
+	}
+}
+
+fn test_map_clear_in_loop_delete_keys() {
+	mut ints := map[int]int{}
+	for i in 0 .. 100 {
+		ints[i] = i * 123
+		ints[i + 2] = i
+		ints.delete(i)
+		ints.delete(i + 1)
+		ints.delete(i + 2)
+		ints.delete(i + 3)
+		ints.delete(i + 4)
+		ints.clear()
+		assert ints.len == 0
+		// dump(ints)
+		ints[i] = 5
+		// dump(ints)
+		assert ints.len == 1
+		ints[1000 + i] = 1000 * i
+		assert ints.len == 2
+	}
+}