From 2242b12c09562b0227c8ee875750930f42b06b50 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Thu, 21 Dec 2023 16:37:44 +0000
Subject: Check that we're not using placeholder unrelocatable values

---
 .../wasm/structure/binary/WasmBinaryWriter.java    | 27 +++++++++++-----------
 1 file changed, 14 insertions(+), 13 deletions(-)

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/backends/wasm/structure/binary/WasmBinaryWriter.java b/src/main/java/org/shedlang/compiler/backends/wasm/structure/binary/WasmBinaryWriter.java
index bb931c65..0c35db7e 100644
--- a/src/main/java/org/shedlang/compiler/backends/wasm/structure/binary/WasmBinaryWriter.java
+++ b/src/main/java/org/shedlang/compiler/backends/wasm/structure/binary/WasmBinaryWriter.java
@@ -60,7 +60,7 @@ public class WasmBinaryWriter {
         var funcIndex = indexTable.funcIndex(funcName);
         writeRelocatableIndex(
             WasmRelocationType.FUNCTION_INDEX_LEB,
-            funcIndex.value(),
+            OptionalInt.of(funcIndex.value()),
             new WasmRelocatableIndex.FuncIndex(funcName)
         );
     }
@@ -69,7 +69,7 @@ public class WasmBinaryWriter {
         var globalIndex = indexTable.globalIndex(globalName);
         writeRelocatableIndex(
             WasmRelocationType.GLOBAL_INDEX_LEB,
-            globalIndex.value(),
+            OptionalInt.of(globalIndex.value()),
             new WasmRelocatableIndex.GlobalIndex(globalName)
         );
     }
@@ -77,8 +77,7 @@ public class WasmBinaryWriter {
     public void writeMemoryAddressConst(WasmMemoryAddress index) throws IOException {
         writeRelocatableIndex(
             WasmRelocationType.MEMORY_ADDR_SLEB,
-            // TODO: use actual value? Or throw if not in relocatable section?
-            0,
+            OptionalInt.empty(),
             new WasmRelocatableIndex.MemoryAddress(index)
         );
     }
@@ -90,8 +89,7 @@ public class WasmBinaryWriter {
     public void writeTableElementIndexConst(WasmFuncName funcName) throws IOException {
         writeRelocatableIndex(
             WasmRelocationType.TABLE_INDEX_SLEB,
-            // TODO: use actual value? Or throw if not in relocatable section?
-            0,
+            OptionalInt.empty(),
             new WasmRelocatableIndex.TableElementIndex(funcName)
         );
     }
@@ -100,7 +98,7 @@ public class WasmBinaryWriter {
         var tagIndex = indexTable.tagIndex(tag);
         writeRelocatableIndex(
             WasmRelocationType.TAG_INDEX_LEB,
-            tagIndex.value(),
+            OptionalInt.of(tagIndex.value()),
             new WasmRelocatableIndex.TagIndex(tag)
         );
     }
@@ -109,14 +107,14 @@ public class WasmBinaryWriter {
         var typeIndex = indexTable.typeIndex(funcType);
         writeRelocatableIndex(
             WasmRelocationType.TYPE_INDEX_LEB,
-            typeIndex.value(),
+            OptionalInt.of(typeIndex.value()),
             new WasmRelocatableIndex.TypeIndex(funcType)
         );
     }
 
     private void writeRelocatableIndex(
         WasmRelocationType relocationType,
-        int unrelocatedIndex,
+        OptionalInt unrelocatedIndex,
         WasmRelocatableIndex index
     ) throws IOException {
         // TODO: handle custom sections?
@@ -125,11 +123,12 @@ public class WasmBinaryWriter {
             .orElse(false);
 
         if (isRelocatable) {
+            var value = unrelocatedIndex.orElse(0);
             var sectionContentsOffset = writer.position() - sectionContentsStart;
             if (relocationType.isSigned()) {
-                writePaddedSignedInt32(unrelocatedIndex);
+                writePaddedSignedInt32(value);
             } else {
-                writePaddedUnsignedInt32(unrelocatedIndex);
+                writePaddedUnsignedInt32(value);
             }
 
             if (!relocationEntries.containsKey(sectionIndex)) {
@@ -141,11 +140,13 @@ public class WasmBinaryWriter {
                 sectionContentsOffset,
                 index
             ));
+        } else if (unrelocatedIndex.isEmpty()) {
+            throw new IllegalStateException("cannot write memory address outside of relocatable section");
         } else {
             if (relocationType.isSigned()) {
-                writeSignedInt32(unrelocatedIndex);
+                writeSignedInt32(unrelocatedIndex.getAsInt());
             } else {
-                writeUnsignedInt32(unrelocatedIndex);
+                writeUnsignedInt32(unrelocatedIndex.getAsInt());
             }
         }
     }
-- 
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