Zero out GC children with explicit memory stores

15 files changed, 177 insertions, 21 deletions

diff --git a/runtime/src/gc.c b/runtime/src/gc.c
index b15c20dc..8d2efc08 100644
--- a/runtime/src/gc.c
+++ b/runtime/src/gc.c
@@ -87,12 +87,6 @@ void* shed__runtime__gc_alloc(size_t size, uint32_t children_offset, uint32_t ch
     object->children_offset = children_offset;
     object->children_count = children_count;
 
-    __builtin_memset(
-        ((void*) object) + children_offset,
-        0,
-        sizeof(void*) * children_count
-    );
-
     // TODO: is it possible to leave adding the root to the caller, and avoid
     // having to add so many roots? (Since some values will immediately become a
     // descendant of a root.)
diff --git a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineEffectTests]/[method:canGenerateCodeForDefineEffect(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineEffectTests]/[method:canGenerateCodeForDefineEffect(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
index f06a5f47..5475f888 100644
--- a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineEffectTests]/[method:canGenerateCodeForDefineEffect(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
+++ b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineEffectTests]/[method:canGenerateCodeForDefineEffect(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
@@ -74,6 +74,20 @@ Instructions:
 
 (
     (call (local "userDefinedEffectPointer__State__0") "shed__runtime__gc_alloc" ((int-const (byte-size-of (struct ((struct (data-ptr int int32 int32)) (struct (int int)))))) (int32-const (byte-offset-of (struct ((struct (data-ptr int int32 int32)) (struct (int int)))) (1))) (int32-const 2)))
+    (
+        memory-store
+        pointer=(local "userDefinedEffectPointer__State__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (int int))))
+        offset=(1 0)
+        value=(int-const 0)
+    )
+    (
+        memory-store
+        pointer=(local "userDefinedEffectPointer__State__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (int int))))
+        offset=(1 1)
+        value=(int-const 0)
+    )
     (call (local "closurePointer__read__0") "shed__runtime__gc_alloc" ((int-const (byte-size-of (struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct ()))))))) (int32-const (byte-offset-of (struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct ()))))) (1 2))) (int32-const 0)))
     (
         memory-store
diff --git a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:canCaptureFreeVariablesThatAreSetAfterDefinition(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:canCaptureFreeVariablesThatAreSetAfterDefinition(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
index 00c9a799..7ffd8bed 100644
--- a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:canCaptureFreeVariablesThatAreSetAfterDefinition(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
+++ b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:canCaptureFreeVariablesThatAreSetAfterDefinition(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
@@ -73,6 +73,20 @@ Instructions:
         memory-store
         pointer=(local "closurePointer__f__0")
         layout=(struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct (int int))))))
+        offset=(1 2 0)
+        value=(int-const 0)
+    )
+    (
+        memory-store
+        pointer=(local "closurePointer__f__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct (int int))))))
+        offset=(1 2 1)
+        value=(int-const 0)
+    )
+    (
+        memory-store
+        pointer=(local "closurePointer__f__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct (int int))))))
         offset=(1 0)
         value=(function-ptr-const "shed__function__f__0")
     )
diff --git a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:immutableFreeVariablesAreStoredInAndLoadedFromEnvironment(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:immutableFreeVariablesAreStoredInAndLoadedFromEnvironment(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
index b2251c34..b2b20774 100644
--- a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:immutableFreeVariablesAreStoredInAndLoadedFromEnvironment(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
+++ b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:immutableFreeVariablesAreStoredInAndLoadedFromEnvironment(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
@@ -73,6 +73,20 @@ Instructions:
         memory-store
         pointer=(local "closurePointer__f__0")
         layout=(struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct (int int))))))
+        offset=(1 2 0)
+        value=(int-const 0)
+    )
+    (
+        memory-store
+        pointer=(local "closurePointer__f__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct (int int))))))
+        offset=(1 2 1)
+        value=(int-const 0)
+    )
+    (
+        memory-store
+        pointer=(local "closurePointer__f__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct (int int))))))
         offset=(1 0)
         value=(function-ptr-const "shed__function__f__0")
     )
diff --git a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:pointersToFreeMutableVariablesAreStoredInAndLoadedFromEnvironment(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:pointersToFreeMutableVariablesAreStoredInAndLoadedFromEnvironment(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
index 9df8efff..cece95b3 100644
--- a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:pointersToFreeMutableVariablesAreStoredInAndLoadedFromEnvironment(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
+++ b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:pointersToFreeMutableVariablesAreStoredInAndLoadedFromEnvironment(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
@@ -73,6 +73,20 @@ Instructions:
         memory-store
         pointer=(local "closurePointer__f__0")
         layout=(struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct (data-ptr data-ptr))))))
+        offset=(1 2 0)
+        value=(data-ptr-const null)
+    )
+    (
+        memory-store
+        pointer=(local "closurePointer__f__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct (data-ptr data-ptr))))))
+        offset=(1 2 1)
+        value=(data-ptr-const null)
+    )
+    (
+        memory-store
+        pointer=(local "closurePointer__f__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct (data-ptr data-ptr))))))
         offset=(1 0)
         value=(function-ptr-const "shed__function__f__0")
     )
diff --git a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:positionalAndNamedParamsAreDefined(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:positionalAndNamedParamsAreDefined(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
index dada1615..1d906b97 100644
--- a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:positionalAndNamedParamsAreDefined(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
+++ b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineFunctionTests]/[method:positionalAndNamedParamsAreDefined(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
@@ -81,6 +81,20 @@ Instructions:
         memory-store
         pointer=(local "closurePointer__f__0")
         layout=(struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct (int int))))))
+        offset=(1 2 0)
+        value=(int-const 0)
+    )
+    (
+        memory-store
+        pointer=(local "closurePointer__f__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct (int int))))))
+        offset=(1 2 1)
+        value=(int-const 0)
+    )
+    (
+        memory-store
+        pointer=(local "closurePointer__f__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (function-ptr (struct ()) (struct (int int))))))
         offset=(1 0)
         value=(function-ptr-const "shed__function__f__0")
     )
diff --git a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineStructTests]/[method:canGenerateCodeForDefineStruct(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineStructTests]/[method:canGenerateCodeForDefineStruct(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
index 8d3e1d22..665acac6 100644
--- a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineStructTests]/[method:canGenerateCodeForDefineStruct(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
+++ b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioDefineStructTests]/[method:canGenerateCodeForDefineStruct(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
@@ -25,6 +25,20 @@ Compilation unit elements:
             memory-store
             pointer=(local "structValuePointer__0")
             layout=(struct ((struct (data-ptr int int32 int32)) (struct (int (struct (int int))))))
+            offset=(1 1 0)
+            value=(int-const 0)
+        )
+        (
+            memory-store
+            pointer=(local "structValuePointer__0")
+            layout=(struct ((struct (data-ptr int int32 int32)) (struct (int (struct (int int))))))
+            offset=(1 1 1)
+            value=(int-const 0)
+        )
+        (
+            memory-store
+            pointer=(local "structValuePointer__0")
+            layout=(struct ((struct (data-ptr int int32 int32)) (struct (int (struct (int int))))))
             offset=(1 0)
             value=(int-const 0)
         )
diff --git a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioNamespaceTests]/[method:canDefineNamespace(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioNamespaceTests]/[method:canDefineNamespace(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
index ddc72f15..b2bde483 100644
--- a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioNamespaceTests]/[method:canDefineNamespace(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
+++ b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioNamespaceTests]/[method:canDefineNamespace(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
@@ -56,6 +56,20 @@
             (call (local "namespaceValue__0") "shed__runtime__gc_alloc" ((int-const (byte-size-of (struct ((struct (data-ptr int int32 int32)) (struct (int int)))))) (int32-const (byte-offset-of (struct ((struct (data-ptr int int32 int32)) (struct (int int)))) (1))) (int32-const 2)))
             (
                 memory-store
+                pointer=(local "namespaceValue__0")
+                layout=(struct ((struct (data-ptr int int32 int32)) (struct (int int))))
+                offset=(1 0)
+                value=(int-const 0)
+            )
+            (
+                memory-store
+                pointer=(local "namespaceValue__0")
+                layout=(struct ((struct (data-ptr int int32 int32)) (struct (int int))))
+                offset=(1 1)
+                value=(int-const 0)
+            )
+            (
+                memory-store
                 pointer=(data-ptr-const "shed__namespace__An_Example")
                 layout=data-ptr
                 offset=()
diff --git a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioTupleCreateTests]/[method:canGenerateCodeForTupleCreate(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioTupleCreateTests]/[method:canGenerateCodeForTupleCreate(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
index d6376954..f1e57c98 100644
--- a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioTupleCreateTests]/[method:canGenerateCodeForTupleCreate(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
+++ b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioTupleCreateTests]/[method:canGenerateCodeForTupleCreate(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
@@ -26,6 +26,27 @@ Instructions:
         pointer=(local "tuplePointer__0")
         layout=(struct ((struct (data-ptr int int32 int32)) (struct (int int int))))
         offset=(1 0)
+        value=(int-const 0)
+    )
+    (
+        memory-store
+        pointer=(local "tuplePointer__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (int int int))))
+        offset=(1 1)
+        value=(int-const 0)
+    )
+    (
+        memory-store
+        pointer=(local "tuplePointer__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (int int int))))
+        offset=(1 2)
+        value=(int-const 0)
+    )
+    (
+        memory-store
+        pointer=(local "tuplePointer__0")
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (int int int))))
+        offset=(1 0)
         value=(local "tupleElement__0__0")
     )
     (
diff --git a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioVarLoadTests]/[method:canGenerateCodeForVarLoad(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioVarLoadTests]/[method:canGenerateCodeForVarLoad(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
index 6e93849c..80a5a9d5 100644
--- a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioVarLoadTests]/[method:canGenerateCodeForVarLoad(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
+++ b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioVarLoadTests]/[method:canGenerateCodeForVarLoad(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
@@ -12,8 +12,8 @@ Instructions:
         memory-load
         (local "varValue__x__0")
         pointer=(local "local__x")
-        layout=(struct ((struct (data-ptr int int32 int32)) int))
-        offset=(1)
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (int))))
+        offset=(1 0)
     )
 )
 
diff --git a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioVarStoreTests]/[method:canGenerateCodeForVarStore(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioVarStoreTests]/[method:canGenerateCodeForVarStore(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
index bd2b4eaf..feea5bf2 100644
--- a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioVarStoreTests]/[method:canGenerateCodeForVarStore(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
+++ b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioVarStoreTests]/[method:canGenerateCodeForVarStore(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
@@ -10,8 +10,8 @@ Instructions:
     (
         memory-store
         pointer=(local "local__x")
-        layout=(struct ((struct (data-ptr int int32 int32)) int))
-        offset=(1)
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (int))))
+        offset=(1 0)
         value=(local "b")
     )
 )
diff --git a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioVarStoreTests]/[method:canStoreIntoVarMultipleTimes(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioVarStoreTests]/[method:canStoreIntoVarMultipleTimes(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
index 2dd55297..08d01b4d 100644
--- a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioVarStoreTests]/[method:canStoreIntoVarMultipleTimes(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
+++ b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.shidtopatio.ShidToPatioVarStoreTests]/[method:canStoreIntoVarMultipleTimes(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
@@ -10,15 +10,15 @@ Instructions:
     (
         memory-store
         pointer=(local "local__x")
-        layout=(struct ((struct (data-ptr int int32 int32)) int))
-        offset=(1)
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (int))))
+        offset=(1 0)
         value=(local "b")
     )
     (
         memory-store
         pointer=(local "local__x")
-        layout=(struct ((struct (data-ptr int int32 int32)) int))
-        offset=(1)
+        layout=(struct ((struct (data-ptr int int32 int32)) (struct (int))))
+        offset=(1 0)
         value=(local "a")
     )
 )
diff --git a/src/main/java/org/shedlang/compiler/patio/types/PatioOffsets.java b/src/main/java/org/shedlang/compiler/patio/types/PatioOffsets.java
index f427bd41..5a3be3ff 100644
--- a/src/main/java/org/shedlang/compiler/patio/types/PatioOffsets.java
+++ b/src/main/java/org/shedlang/compiler/patio/types/PatioOffsets.java
@@ -1,6 +1,9 @@
 package org.shedlang.compiler.patio.types;
 
 import org.pcollections.PVector;
+import org.pcollections.TreePVector;
+
+import java.util.List;
 
 public class PatioOffsets {
     private PatioOffsets() {
@@ -8,6 +11,16 @@ public class PatioOffsets {
 
     public static PatioDataLayout offsetDataLayout(
         PatioDataLayout patioDataLayout,
+        List<Integer> patioOffsets
+    ) {
+        return offsetDataLayout(
+            patioDataLayout,
+            TreePVector.from(patioOffsets)
+        );
+    }
+
+    public static PatioDataLayout offsetDataLayout(
+        PatioDataLayout patioDataLayout,
         PVector<Integer> patioOffsets
     ) {
         // TODO: check that offset is valid?
diff --git a/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioGc.java b/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioGc.java
index 351dee49..4bb7c3a3 100644
--- a/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioGc.java
+++ b/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioGc.java
@@ -3,11 +3,10 @@ package org.shedlang.compiler.shidtopatio;
 import org.shedlang.compiler.patio.PatioFunctionDeclaration;
 import org.shedlang.compiler.patio.PatioLocal;
 import org.shedlang.compiler.patio.instructions.PatioCall;
-import org.shedlang.compiler.patio.operands.PatioInt32Const;
-import org.shedlang.compiler.patio.operands.PatioIntConst;
-import org.shedlang.compiler.patio.operands.PatioLocalRef;
-import org.shedlang.compiler.patio.operands.PatioOperand;
+import org.shedlang.compiler.patio.instructions.PatioMemoryStore;
+import org.shedlang.compiler.patio.operands.*;
 import org.shedlang.compiler.patio.types.*;
+import org.shedlang.compiler.patio.values.PatioDataPtrValueNull;
 import org.shedlang.compiler.patio.values.PatioIntValueByteOffsetOf;
 import org.shedlang.compiler.patio.values.PatioIntValueByteSizeOf;
 import org.shedlang.compiler.sources.Source;
@@ -154,12 +153,39 @@ public class ShidToPatioGc {
 
         var offset = new PatioInt32Const(new PatioIntValueByteOffsetOf(layout, childrenOffset));
 
-        return context.addInstruction(new PatioCall(
+        context = context.addInstruction(new PatioCall(
             Optional.of(destination),
             ALLOC.name(),
             List.of(size, offset, PatioInt32Const.of(childrenCount)),
             source
         ));
+
+        for (var childIndex = 0; childIndex < childrenCount; childIndex++) {
+            var childOffset = Lists.concat(childrenOffset, List.of(childIndex));
+            var childDataLayout = PatioOffsets.offsetDataLayout(layout, childOffset);
+
+            var zero = switch (childDataLayout) {
+                case PatioDataLayoutDataPtr patioDataLayoutDataPtr ->
+                    new PatioDataPtrConst(new PatioDataPtrValueNull());
+
+                case PatioDataLayoutInt dataLayoutInt ->
+                    PatioIntConst.of(0);
+
+                default ->
+                    // TODO: better error
+                    throw new IllegalArgumentException("unsupported child");
+            };
+
+            context = context.addInstruction(new PatioMemoryStore(
+                destination,
+                layout,
+                childOffset,
+                zero,
+                source
+            ));
+        }
+
+        return context;
     }
 
     // == Collection  ==
diff --git a/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioVars.java b/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioVars.java
index 37e30123..34143882 100644
--- a/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioVars.java
+++ b/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioVars.java
@@ -16,9 +16,13 @@ public class ShidToPatioVars {
     }
 
     private static final PatioDataLayout VAR_DATA_LAYOUT =
-        ShidToPatioGc.gcObjectDataLayout(PatioDataLayouts.fromType(ShidToPatioTypes.VALUE_TYPE));
+        ShidToPatioGc.gcObjectDataLayout(
+            PatioDataLayouts.struct(List.of(
+                PatioDataLayouts.fromType(ShidToPatioTypes.VALUE_TYPE)
+            ))
+        );
 
-    private static final List<Integer> VALUE_OFFSET = ShidToPatioGc.gcObjectOffset(List.of());
+    private static final List<Integer> VALUE_OFFSET = ShidToPatioGc.gcObjectOffset(List.of(0));
     private static final List<Integer> GC_CHILDREN_OFFSET = ShidToPatioGc.gcObjectOffset(List.of());
     private static final int GC_CHILDREN_COUNT = 1;