Cycle collector. (#175)

backend.native/tests/build.gradle

@@ -41,11 +41,11 @@ abstract class KonanTest extends DefaultTask {
         project.javaexec {
             main = 'org.jetbrains.kotlin.cli.bc.K2NativeKt'
             classpath = project.configurations.cli_bc
-            jvmArgs "-ea", 
+            jvmArgs "-ea",
                 "-Dkonan.home=${dist.canonicalPath}",
                 "-Djava.library.path=${dist.canonicalPath}/konan/nativelib"
             args("-output", output,
-                 source, 
+                 source,
                  *moreArgs,
                  *project.globalArgs)
         }
@@ -88,7 +88,7 @@ abstract class KonanTest extends DefaultTask {
 
 class RunKonanTest extends KonanTest {
     void compileTest(String source, String exe) {
-        runCompiler(source, exe, []) 
+        runCompiler(source, exe, [])
     }
 }
 
@@ -98,7 +98,7 @@ class LinkKonanTest extends KonanTest {
     void compileTest(String source, String exe) {
         def libDir = project.file(lib).absolutePath
         def libBc = "${libDir}.bc"
-        
+
         runCompiler(lib, libBc, ['-nolink', '-nostdlib'])
         runCompiler(source, exe, ['-library', libBc])
     }
@@ -246,8 +246,8 @@ task tostring3(type: RunKonanTest) {
             "1.17549E-38\n3.40282E+38\n-INF\nINF\n" +
             // Linux version prints -NAN.
             // "NAN\n" +
-            "4.94066E-324\n1.79769E+308\n-INF\nINF\n" 
-            // "NAN\n" 
+            "4.94066E-324\n1.79769E+308\n-INF\nINF\n"
+            // "NAN\n"
     source = "runtime/basic/tostring3.kt"
 }
 
@@ -359,7 +359,7 @@ task intrinsic(type: RunKonanTest) {
 }
 
 /*
-    Disabled until we extract the classes that should be 
+    Disabled until we extract the classes that should be
     always present from stdlib.kt.bc into a separate binary.
 
 task link(type: LinkKonanTest) {
@@ -805,6 +805,11 @@ task memory_throw_cleanup(type: RunKonanTest) {
     source = "runtime/memory/throw_cleanup.kt"
 }
 
+task memory_collect_cycles(type: RunKonanTest) {
+    goldValue = "42\n"
+    source = "runtime/memory/cycles0.kt"
+}
+
 task unit1(type: RunKonanTest) {
     goldValue = "First\nkotlin.Unit\n"
     source = "codegen/basics/unit1.kt"

backend.native/tests/runtime/memory/cycles0.kt

@@ -0,0 +1,45 @@
+data class Node(val data: Int, var next: Node?, var prev: Node?, val outer: Node?)
+
+fun makeCycle(len: Int, outer: Node?): Node {
+    val start = Node(0, null, null, outer)
+    var prev = start
+    for (i in 1 .. len - 1) {
+        prev = Node(i, prev, null, outer)
+    }
+    start.next = prev
+    return start
+}
+
+fun makeDoubleCycle(len: Int): Node {
+    val start = makeCycle(len, null)
+    var prev = start
+    var cur = prev.next
+    while (cur != start) {
+        cur!!.prev = prev
+        prev = cur
+        cur = cur.next
+    }
+    start.prev = prev
+    return start
+}
+
+fun createCycles(junk: Node) {
+    val cycle1 = makeCycle(1, junk)
+    val cycle2 = makeCycle(2, junk)
+    val cycle10 = makeCycle(10, junk)
+    val cycle100 = makeCycle(100, junk)
+    val dcycle1 = makeDoubleCycle(1)
+    val dcycle2 = makeDoubleCycle(2)
+    val dcycle10 = makeDoubleCycle(10)
+    val dcycle100 = makeDoubleCycle(100)
+
+}
+
+fun main(args : Array<String>) {
+    // Create outer link from cyclic garbage.
+    val outer = Node(42, null, null, null)
+    createCycles(outer)
+    konan.internal.GC.collect()
+    // Ensure outer is not collected.
+    println(outer.data)
+}