Introduce Java Object Layout to the codebase and write tests for core primitives (#3391)

It should further simplify reasoning about new fields in core classes

Author: qwwdfsad

kotlinx-coroutines-core/build.gradle

@@ -168,6 +168,7 @@ kotlin.sourceSets {
         api "org.jetbrains.kotlinx:lincheck:$lincheck_version"
         api "org.jetbrains.kotlinx:kotlinx-knit-test:$knit_version"
         implementation project(":android-unit-tests")
+        implementation "org.openjdk.jol:jol-core:0.16"
     }
 }
 

kotlinx-coroutines-core/jvm/test/MemoryFootprintTest.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2016-2022 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package kotlinx.coroutines
+
+import org.junit.Test
+import org.openjdk.jol.info.ClassLayout
+import kotlin.test.*
+
+
+class MemoryFootprintTest : TestBase(true) {
+
+    @Test
+    fun testJobLayout() = assertLayout(Job().javaClass, 24)
+
+    @Test
+    fun testCancellableContinuationFootprint() = assertLayout(CancellableContinuationImpl::class.java, 48)
+
+    private fun assertLayout(clz: Class<*>, expectedSize: Int) {
+        val size = ClassLayout.parseClass(clz).instanceSize()
+//        println(ClassLayout.parseClass(clz).toPrintable())
+        assertEquals(expectedSize.toLong(), size)
+    }
+}