Bring compartment stack management under compiler control

lib/CodeGen.cs

@@ -3645,11 +3645,14 @@ public class DowncallReceiver : CallReceiver {
             return null;
         }
         public static object push_compartment(object[] args) {
-            Compartment.Push();
-            return null;
+            var old = Compartment.Top;
+            Compartment.Top = new Compartment();
+            Kernel.InitCompartment();
+            return Handle.Wrap(old);
         }
         public static object pop_compartment(object[] args) {
-            Compartment.Pop();
+            Compartment.Top.RunEnd();
+            Compartment.Top = (Compartment)Handle.Unbox(args[1]);
             return null;
         }
         public static object new_unit(object[] args) {

lib/Kernel.cs

@@ -4624,34 +4624,39 @@ public class Compartment {
         internal static void BeforeExit(object sender, EventArgs args) {
             if (disable_end) return;
             disable_end = true;
-            while (Top.prev != null) { Pop(); }
-            Top.end.Run();
+
+            while (true) {
+                Compartment tokill = null;
+                lock (pending) {
+                    if (pending.Count > 0) tokill = ((IEnumerable<Compartment>)pending).GetEnumerator().Current;
+                }
+                if (tokill == null) break;
+                tokill.RunEnd();
+            }
+
             // XXX is this really the best place?
             Builtins.stdout.Flush();
             Builtins.stderr.Flush();
         }
 
-        Compartment prev;
-        private Compartment() { }
+        internal Compartment() { lock(pending) pending.Add(this); }
 
+        [TrueGlobal]
+        internal static HashSet<Compartment> pending = new HashSet<Compartment>();
         [TrueGlobal]
         public static Compartment Top = new Compartment();
+        internal bool end_run;
 
         internal PhaserList check = new PhaserList(true);
         internal PhaserList init  = new PhaserList(false);
         internal PhaserList end   = new PhaserList(true);
 
-        internal static void Push() {
-            Compartment n = new Compartment();
-            n.prev = Top;
-
-            Top = n;
-            Kernel.InitCompartment();
-        }
+        internal void RunEnd() {
+            if (end_run) return;
+            end_run = true;
+            lock(pending) pending.Remove(this);
 
-        internal static void Pop() {
-            Top.end.Run();
-            Top = Top.prev;
+            end.Run();
         }
 
         // and here's a bunch of smart constructors

src/NieczaBackendDotnet.pm6

@@ -342,7 +342,7 @@ class Unit {
 }
 
 method push_compartment() { downcall("push_compartment") }
-method pop_compartment() { downcall("pop_compartment") }
+method pop_compartment($c) { downcall("pop_compartment", $c) }
 method get_codepoint($str) { downcall("get_codepoint", $str) }
 
 method create_unit($name, $filename, $source, $main, $run) {

src/NieczaFrontendSTD.pm6

@@ -269,8 +269,8 @@ method parse(:$unitname, :$filename, :$source, :$outer, :$run, :$main, :$evalmod
     my $*UNIT;
     my $*CCSTATE; my $*BORG; my %*RX; my $*XACT; my $*VAR; my $*IN_REDUCE;
 
-    $*backend.push_compartment unless $evalmode;
-    LEAVE { $*backend.pop_compartment unless $evalmode };
+    my $oldc = $*backend.push_compartment unless $evalmode;
+    LEAVE { $*backend.pop_compartment($oldc) unless $evalmode };
     my $*unit = $*backend.create_unit($unitname, $filename, $*no_incl_source ?? $Backend.gethash($source) !! $source, $main, $run);
     my $*settingref = $*niecza_outer_ref ||
         ($lang ne 'NULL' ?? $*unit.need_unit($lang).bottom !! Any);