WASM: add flag that allows to insert assertions before each memory access in C code

core/src/main/java/org/teavm/backend/wasm/WasmTarget.java

@@ -375,7 +375,8 @@ public class WasmTarget implements TeaVMTarget {
 
     private void emitC(WasmModule module, BuildTarget buildTarget, String outputName) throws IOException {
         WasmCRenderer renderer = new WasmCRenderer();
-        //renderer.setLineNumbersEmitted(debugging);
+        renderer.setLineNumbersEmitted(Boolean.parseBoolean(System.getProperty("wasm.c.lineNumbers", "false")));
+        renderer.setMemoryAccessChecked(Boolean.parseBoolean(System.getProperty("wasm.c.assertMemory", "false")));
         renderer.render(module);
         try (OutputStream output = buildTarget.createResource(outputName);
                 Writer writer = new OutputStreamWriter(output, "UTF-8")) {

core/src/main/java/org/teavm/backend/wasm/render/WasmCRenderer.java

@@ -30,6 +30,7 @@ public class WasmCRenderer {
     String currentFile = "";
     int currentLine = -1;
     boolean lineNumbersEmitted;
+    boolean memoryAccessChecked;
     TextLocation lastReportedLocation;
 
     public boolean isLineNumbersEmitted() {
@@ -40,6 +41,14 @@ public class WasmCRenderer {
         this.lineNumbersEmitted = value;
     }
 
+    public boolean isMemoryAccessChecked() {
+        return memoryAccessChecked;
+    }
+
+    public void setMemoryAccessChecked(boolean memoryAccessChecked) {
+        this.memoryAccessChecked = memoryAccessChecked;
+    }
+
     void indent() {
         ++indentLevel;
     }
@@ -141,6 +150,7 @@ public class WasmCRenderer {
     private void renderFunction(WasmFunction function) {
         WasmCRenderingVisitor visitor = new WasmCRenderingVisitor(function.getResult(),
                 function.getLocalVariables().size(), function.getModule());
+        visitor.setMemoryAccessChecked(memoryAccessChecked);
 
         StringBuilder declaration = new StringBuilder();
         renderFunctionModifiers(declaration, function);

core/src/main/java/org/teavm/backend/wasm/render/WasmCRenderingVisitor.java

@@ -71,6 +71,7 @@ class WasmCRenderingVisitor implements WasmExpressionVisitor {
     private WasmModule module;
     private String[] localVariableNames;
     private Set<String> usedVariableNames = new HashSet<>();
+    private boolean memoryAccessChecked;
 
     WasmCRenderingVisitor(WasmType functionType, int variableCount, WasmModule module) {
         localVariableNames = new String[variableCount];
@@ -78,6 +79,14 @@ class WasmCRenderingVisitor implements WasmExpressionVisitor {
         this.module = module;
     }
 
+    public boolean isMemoryAccessChecked() {
+        return memoryAccessChecked;
+    }
+
+    public void setMemoryAccessChecked(boolean memoryAccessChecked) {
+        this.memoryAccessChecked = memoryAccessChecked;
+    }
+
     public CExpression getValue() {
         return value;
     }
@@ -699,8 +708,8 @@ class WasmCRenderingVisitor implements WasmExpressionVisitor {
 
         requiredType = WasmType.INT32;
         expression.getSelector().acceptVisitor(this);
-        value = cacheIfNeeded(WasmType.INT32, value, result);
         result.getLines().addAll(value.getLines());
+        value = cacheIfNeeded(WasmType.INT32, value, result);
         sb.append("wasm_table[" + value.getText() + "])(");
         translateArguments(expression.getArguments(), expression.getParameterTypes(), result, sb);
         sb.append(")");
@@ -761,7 +770,7 @@ class WasmCRenderingVisitor implements WasmExpressionVisitor {
 
         requiredType = WasmType.INT32;
         expression.getIndex().acceptVisitor(this);
-        CExpression index = value;
+        CExpression index = checkAddress(value);
         if (type == null) {
             value = index;
             return;
@@ -796,7 +805,7 @@ class WasmCRenderingVisitor implements WasmExpressionVisitor {
 
         requiredType = WasmType.INT32;
         expression.getIndex().acceptVisitor(this);
-        CExpression index = value;
+        CExpression index = checkAddress(value);
         if (type == null) {
             value = index;
             return;
@@ -837,7 +846,7 @@ class WasmCRenderingVisitor implements WasmExpressionVisitor {
 
         requiredType = WasmType.INT32;
         expression.getIndex().acceptVisitor(this);
-        CExpression index = value;
+        CExpression index = checkAddress(value);
         if (type == null) {
             value = index;
             return;
@@ -856,7 +865,7 @@ class WasmCRenderingVisitor implements WasmExpressionVisitor {
 
         requiredType = WasmType.INT32;
         expression.getIndex().acceptVisitor(this);
-        CExpression index = value;
+        CExpression index = checkAddress(value);
         if (type == null) {
             value = index;
             return;
@@ -874,7 +883,7 @@ class WasmCRenderingVisitor implements WasmExpressionVisitor {
 
         requiredType = WasmType.INT32;
         expression.getIndex().acceptVisitor(this);
-        CExpression index = value;
+        CExpression index = checkAddress(value);
 
         requiredType = WasmType.INT32;
         expression.getValue().acceptVisitor(this);
@@ -914,7 +923,7 @@ class WasmCRenderingVisitor implements WasmExpressionVisitor {
 
         requiredType = WasmType.INT32;
         expression.getIndex().acceptVisitor(this);
-        CExpression index = value;
+        CExpression index = checkAddress(value);
 
         requiredType = WasmType.INT64;
         expression.getValue().acceptVisitor(this);
@@ -961,7 +970,7 @@ class WasmCRenderingVisitor implements WasmExpressionVisitor {
 
         requiredType = WasmType.INT32;
         expression.getIndex().acceptVisitor(this);
-        CExpression index = value;
+        CExpression index = checkAddress(value);
 
         requiredType = WasmType.FLOAT32;
         expression.getValue().acceptVisitor(this);
@@ -982,7 +991,7 @@ class WasmCRenderingVisitor implements WasmExpressionVisitor {
 
         requiredType = WasmType.INT32;
         expression.getIndex().acceptVisitor(this);
-        CExpression index = value;
+        CExpression index = checkAddress(value);
 
         requiredType = WasmType.FLOAT64;
         expression.getValue().acceptVisitor(this);
@@ -997,6 +1006,27 @@ class WasmCRenderingVisitor implements WasmExpressionVisitor {
         value = result;
     }
 
+    private CExpression checkAddress(CExpression index) {
+        if (!memoryAccessChecked) {
+            return index;
+        }
+
+        CExpression checked = new CExpression();
+        checked.getLines().addAll(index.getLines());
+        String var;
+        if (!index.isRelocatable()) {
+            var = "tmp_" + temporaryIndex++;
+            checked.addLine("int32_t " + var + " = " + index.getText() + ";");
+        } else {
+            var = index.getText();
+        }
+        checked.addLine("assert(" + var + " < " + module.getMemorySize() * 65536 + ");");
+        checked.setText(var);
+        checked.setRelocatable(index.isRelocatable());
+
+        return checked;
+    }
+
     private CLine declareVariable(String name, WasmType type) {
         return new CSingleLine(mapType(type) + " " + name + ";");
     }