diff --git a/package.json b/package.json
index ca5f2564..4f7207a0 100644
--- a/package.json
+++ b/package.json
@@ -63,6 +63,7 @@
     "test-web": "nightwatch -e chrome test/web",
     "start": "electron .",
     "fuzzbasic": "jsfuzz gen/common/basic/fuzz.js ~/basic/corpus/ --versifier false",
+    "fuzzhdl": "jsfuzz -r binaryen gen/common/hdl/fuzz.js ~/verilator/corpus/ --versifier false",
     "machine": "node gen/tools/runmachine.js",
     "mkdoc": "typedoc --out web/jsdoc src/common/"
   },
diff --git a/src/common/hdl/fuzz.ts b/src/common/hdl/fuzz.ts
new file mode 100644
index 00000000..4687f3b9
--- /dev/null
+++ b/src/common/hdl/fuzz.ts
@@ -0,0 +1,35 @@
+
+//import binaryen = require('binaryen');
+import { HDLModuleJS } from "./hdlruntime";
+import { HDLModuleWASM } from "./hdlwasm";
+import { CompileError, VerilogXMLParser } from "./vxmlparser";
+
+export function fuzz(buf) {
+    var parser = new VerilogXMLParser();
+    var str = buf.toString();
+    try {
+        parser.parse(str);
+    } catch (e) {
+        if (e instanceof CompileError) return;
+        throw e;
+    }
+    /*
+    if (0) {
+        var wmod = new HDLModuleWASM(parser.modules['TOP'], parser.modules['@CONST-POOL@']);
+        wmod.traceBufferSize = 0x8000;
+        wmod.maxMemoryMB = 0.25;
+        wmod.init().then(() => {
+            wmod.powercycle();
+            wmod.tick2(10000);
+            wmod.dispose();
+        })
+    }
+    */
+    if (1) {
+        var jmod = new HDLModuleJS(parser.modules['TOP'], parser.modules['@CONST-POOL@']);
+        jmod.init();
+        jmod.powercycle();
+        jmod.tick2(10000);
+        jmod.dispose();
+    }
+}
diff --git a/src/common/hdl/hdlruntime.ts b/src/common/hdl/hdlruntime.ts
index 4d448b39..257dfec0 100644
--- a/src/common/hdl/hdlruntime.ts
+++ b/src/common/hdl/hdlruntime.ts
@@ -1,6 +1,6 @@
 
 import { byteArrayToString, safe_extend } from "../util";
-import { HDLBinop, HDLBlock, HDLConstant, HDLDataType, HDLExpr, HDLExtendop, HDLFuncCall, HDLModuleDef, HDLModuleRunner, HDLTriop, HDLUnop, HDLValue, HDLVariableDef, HDLVarRef, isArrayItem, isArrayType, isBinop, isBlock, isConstExpr, isFuncCall, isLogicType, isTriop, isUnop, isVarDecl, isVarRef, isWhileop } from "./hdltypes";
+import { HDLBinop, HDLBlock, HDLConstant, HDLDataType, HDLExpr, HDLExtendop, HDLFuncCall, HDLModuleDef, HDLModuleRunner, HDLSourceLocation, HDLTriop, HDLUnop, HDLValue, HDLVariableDef, HDLVarRef, isArrayItem, isArrayType, isBigConstExpr, isBinop, isBlock, isConstExpr, isFuncCall, isLogicType, isTriop, isUnop, isVarDecl, isVarRef, isWhileop } from "./hdltypes";
 
 interface VerilatorUnit {
     _ctor_var_reset(state) : void;
@@ -10,6 +10,18 @@ interface VerilatorUnit {
     _change_request(state) : boolean;
 }
 
+export class HDLError extends Error {
+    obj: any;
+    $loc: HDLSourceLocation;
+    constructor(obj: any, msg: string) {
+        super(msg);
+        Object.setPrototypeOf(this, HDLError.prototype);
+        this.obj = obj;
+        if (obj && obj.$loc) this.$loc = obj.$loc;
+        if (obj) console.log(obj);
+    }
+}
+
 export class HDLModuleJS implements HDLModuleRunner {
 
     mod: HDLModuleDef;
@@ -114,7 +126,7 @@ export class HDLModuleJS implements HDLModuleRunner {
                 return;
             }
         }
-        throw new Error(`model did not converge on reset()`)
+        throw new HDLError(null, `model did not converge on reset()`)
     }
 
     eval() {
@@ -139,7 +151,7 @@ export class HDLModuleJS implements HDLModuleRunner {
                 return;
             }
         }
-        throw new Error(`model did not converge on eval()`)
+        throw new HDLError(null, `model did not converge on eval()`)
     }
 
     tick2(iters: number) {
@@ -180,20 +192,20 @@ export class HDLModuleJS implements HDLModuleRunner {
                     if (isArrayItem(e) && isConstExpr(e.expr)) {
                         arr[e.index] = e.expr.cvalue;
                     } else {
-                        throw new Error(`non-const expr in initarray`);
+                        throw new HDLError(dt, `non-const expr in initarray`);
                     }
                 }
             }
             return arr;
         }
-        throw new Error(`no default value for var type: ${vardef.name}`);
+        throw new HDLError(dt, `no default value for var type: ${vardef.name}`);
     }
 
     constValue(expr: HDLExpr) : number {
         if (isConstExpr(expr)) {
             return expr.cvalue;
         } else {
-            throw new Error(`no const value for expr`);
+            throw new HDLError(expr, `no const value for expr`);
         }
     }
 
@@ -220,7 +232,7 @@ export class HDLModuleJS implements HDLModuleRunner {
                 s += ` = ${this.constValue(e)}`; // TODO?
             } else if (e.initValue != null) {
                 // TODO?
-                throw new Error(`can't init array here`);
+                throw new HDLError(e, `can't init array here`);
             } else if (isLogicType(e.dtype) && e.dtype.left > 31) {
                 // TODO: hack for big ints ($readmem)
                 s += ` = []`;
@@ -228,6 +240,8 @@ export class HDLModuleJS implements HDLModuleRunner {
             return s;
         } else if (isConstExpr(e)) {
             return `0x${e.cvalue.toString(16)}`;
+        } else if (isBigConstExpr(e)) {
+            return e.bigvalue.toString(); // TODO?
         } else if (isTriop(e)) {
             switch (e.op) {
                 case 'if':
@@ -239,8 +253,7 @@ export class HDLModuleJS implements HDLModuleRunner {
                 case 'condbound':
                     return `(${this.expr2js(e.cond, {cond:true})} ? ${this.expr2js(e.left)} : ${this.expr2js(e.right)})`;
                 default:
-                    console.log(e);
-                    throw Error(`unknown triop ${e.op}`);
+                    throw new HDLError(e, `unknown triop ${e.op}`);
             }
         } else if (isBinop(e)) {
             switch (e.op) {
@@ -260,8 +273,7 @@ export class HDLModuleJS implements HDLModuleRunner {
                 default:
                     var jsop = OP2JS[e.op];
                     if (!jsop) {
-                        console.log(e);
-                        throw Error(`unknown binop ${e.op}`)
+                        throw new HDLError(e, `unknown binop ${e.op}`)
                     }
                     if (jsop.startsWith('?')) {
                         jsop = jsop.substr(1);
@@ -287,9 +299,10 @@ export class HDLModuleJS implements HDLModuleRunner {
                 case 'extends':
                     let shift = 32 - (e as HDLExtendop).widthminv;
                     return `((${this.expr2js(e.left)} << ${shift}) >> ${shift})`;
+                case 'redxor':
+                    return `this.$$${e.op}(${this.expr2js(e.left)})`;
                 default:
-                    console.log(e);
-                    throw Error(`unknown unop ${e.op}`);
+                    throw new HDLError(e, `unknown unop ${e.op}`);
             }
         } else if (isBlock(e)) {
             // TODO: { e } ?
@@ -330,11 +343,11 @@ export class HDLModuleJS implements HDLModuleRunner {
                     return `${this.expr2js(e)}.forEach((a) => a.fill(0))`
                 } else {
                     // TODO: 3d arrays?
-                    throw Error(`unsupported data type for reset: ${JSON.stringify(e.dtype)}`);
+                    throw new HDLError(e, `unsupported data type for reset: ${JSON.stringify(e.dtype)}`);
                 }
             }
         } else {
-            throw Error(`can only reset var refs`);
+            throw new HDLError(e, `can only reset var refs`);
         }
     }
 
@@ -379,16 +392,27 @@ export class HDLModuleJS implements HDLModuleRunner {
         var strfn = byteArrayToString(barr); // convert to string
         // parse hex/binary file
         var strdata = this.getFileData(strfn) as string;
-        if (strdata == null) throw Error("Could not $readmem '" + strfn + "'");
+        if (strdata == null) throw new HDLError(null, "Could not $readmem '" + strfn + "'");
         var data = strdata.split('\n').filter(s => s !== '').map(s => parseInt(s, ishex ? 16 : 2));
         console.log('$readmem', ishex, strfn, data.length);
         // copy into destination array
-        if (memp === null) throw Error("No destination array to $readmem " + strfn);
-        if (memp.length < data.length) throw Error("Destination array too small to $readmem " + strfn);
+        if (memp === null) throw new HDLError(null, "No destination array to $readmem " + strfn);
+        if (memp.length < data.length) throw new HDLError(null, "Destination array too small to $readmem " + strfn);
         for (i=0; i<data.length; i++)
             memp[i] = data[i];
     }
 
+    $time(o) {
+        return new Date().getTime();
+    }
+
+    $$redxor(r: number) : number {
+        r=(r^(r>>1)); r=(r^(r>>2)); r=(r^(r>>4)); r=(r^(r>>8)); r=(r^(r>>16));
+        return r;
+    }
+
+    //
+
     isStopped() { return this.stopped; }
     isFinished() { return this.finished; }
     
diff --git a/src/common/hdl/hdlwasm.ts b/src/common/hdl/hdlwasm.ts
index 10fbfb72..ae75df3c 100644
--- a/src/common/hdl/hdlwasm.ts
+++ b/src/common/hdl/hdlwasm.ts
@@ -1,6 +1,7 @@
 
-import { hasDataType, HDLBinop, HDLBlock, HDLConstant, HDLDataType, HDLDataTypeObject, HDLExpr, HDLExtendop, HDLFuncCall, HDLModuleDef, HDLModuleRunner, HDLSourceLocation, HDLTriop, HDLUnop, HDLValue, HDLVariableDef, HDLVarRef, HDLWhileOp, isArrayItem, isArrayType, isBigConstExpr, isBinop, isBlock, isConstExpr, isFuncCall, isLogicType, isTriop, isUnop, isVarDecl, isVarRef, isWhileop } from "./hdltypes";
 import binaryen = require('binaryen');
+import { hasDataType, HDLBinop, HDLBlock, HDLConstant, HDLDataType, HDLDataTypeObject, HDLExpr, HDLExtendop, HDLFuncCall, HDLModuleDef, HDLModuleRunner, HDLSourceLocation, HDLTriop, HDLUnop, HDLValue, HDLVariableDef, HDLVarRef, HDLWhileOp, isArrayItem, isArrayType, isBigConstExpr, isBinop, isBlock, isConstExpr, isFuncCall, isLogicType, isTriop, isUnop, isVarDecl, isVarRef, isWhileop } from "./hdltypes";
+import { HDLError } from "./hdlruntime";
 
 const VERILATOR_UNIT_FUNCTIONS = [
     "_ctor_var_reset",
@@ -27,18 +28,6 @@ const TRACEBUF = "$$tbuf";
 
 ///
 
-export class HDLError extends Error {
-    obj: any;
-    $loc: HDLSourceLocation;
-    constructor(obj: any, msg: string) {
-        super(msg);
-        Object.setPrototypeOf(this, HDLError.prototype);
-        this.obj = obj;
-        if (obj && obj.$loc) this.$loc = obj.$loc;
-        if (obj) console.log(obj);
-    }
-}
-
 function getDataTypeSize(dt: HDLDataType) : number {
     if (isLogicType(dt)) {
         if (dt.left <= 7)
@@ -195,15 +184,13 @@ export class HDLModuleWASM implements HDLModuleRunner {
     traceEndOffset: number;
     trace: any;
     getFileData = null;
+    maxMemoryMB : number;
 
-    constructor(moddef: HDLModuleDef, constpool: HDLModuleDef) {
+    constructor(moddef: HDLModuleDef, constpool: HDLModuleDef, maxMemoryMB?: number) {
         this.hdlmod = moddef;
         this.constpool = constpool;
-        this.bmod = new binaryen.Module();
-        this.genTypes();
-        var membytes = this.globals.len;
-        var memblks = Math.ceil(membytes / 65536);
-        this.bmod.setMemory(memblks, memblks, MEMORY); // memory is in 64k chunks
+        this.maxMemoryMB = maxMemoryMB || 16;
+        this.genMemory();
         this.genFuncs();
     }
 
@@ -300,11 +287,26 @@ export class HDLModuleWASM implements HDLModuleRunner {
         if (this.bmod) {
             this.bmod.dispose();
             this.bmod = null;
+            this.instance = null;
+            this.databuf = null;
+            this.data8 = null;
+            this.data16 = null;
+            this.data32 = null;
         }
     }
 
     //
 
+    private genMemory() {
+        this.bmod = new binaryen.Module();
+        this.genTypes();
+        var membytes = this.globals.len;
+        if (membytes > this.maxMemoryMB*1024*1024)
+            throw new HDLError(null, `cannot allocate ${membytes} bytes, limit is ${this.maxMemoryMB} MB`);
+        var memblks = Math.ceil(membytes / 65536);
+        this.bmod.setMemory(memblks, memblks, MEMORY); // memory is in 64k chunks
+    }
+
     private genTypes() {
         // generate global variables
         var state = new Struct();
diff --git a/src/common/hdl/vxmlparser.ts b/src/common/hdl/vxmlparser.ts
index 3eaa1f11..c622636f 100644
--- a/src/common/hdl/vxmlparser.ts
+++ b/src/common/hdl/vxmlparser.ts
@@ -1,4 +1,5 @@
 
+import { HDLError } from "./hdlruntime";
 import { HDLAlwaysBlock, HDLArrayItem, HDLBinop, HDLBlock, HDLConstant, HDLDataType, HDLDataTypeObject, HDLExpr, HDLExtendop, HDLFile, HDLFuncCall, HDLHierarchyDef, HDLInstanceDef, HDLLogicType, HDLModuleDef, HDLNativeType, HDLPort, HDLSensItem, HDLSourceLocation, HDLTriop, HDLUnit, HDLUnop, HDLUnpackArray, HDLValue, HDLVariableDef, HDLVarRef, HDLWhileOp, isArrayType, isBinop, isBlock, isConstExpr, isFuncCall, isLogicType, isTriop, isUnop, isVarDecl, isVarRef } from "./hdltypes";
 
 /**
@@ -16,6 +17,13 @@ import { HDLAlwaysBlock, HDLArrayItem, HDLBinop, HDLBlock, HDLConstant, HDLDataT
  * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer
  */
 
+ export class CompileError extends Error {
+    constructor(obj: HDLSourceLocation|XMLNode, msg: string) {
+        super(msg);
+        Object.setPrototypeOf(this, CompileError.prototype);
+    }
+}
+
 interface XMLNode {
     type: string;
     text: string | null;
@@ -47,10 +55,11 @@ function parseXMLPoorly(s: string, openfn?: XMLVisitFunction, closefn?: XMLVisit
 
     function closetop() {
         top = stack.pop();
-        if (top.type != ident) throw Error("mismatch close tag: " + ident);
+        if (top == null || top.type != ident) throw new CompileError(node, "mismatch close tag: " + ident);
         if (closefn) {
             top.obj = closefn(top);
         }
+        if (stack.length == 0) throw new CompileError(null, "close tag without open: " + ident);
         stack[stack.length - 1].children.push(top);
     }
     function parseattrs(as: string): { [id: string]: string } {
@@ -79,24 +88,16 @@ function parseXMLPoorly(s: string, openfn?: XMLVisitFunction, closefn?: XMLVisit
             }
             if (attrs && attrs.endsWith('/')) closetop();
         } else if (content != null) {
+            if (stack.length == 0) throw new CompileError(null, "content without element");
             var txt = escapeXML(content as string).trim();
             if (txt.length) stack[stack.length - 1].text = txt;
         }
     }
-    if (stack.length != 1) throw Error("tag not closed");
-    if (stack[0].type != '?xml') throw Error("?xml needs to be first element");
+    if (stack.length != 1) throw new CompileError(null, "tag not closed");
+    if (stack[0].type != '?xml') throw new CompileError(null, "?xml needs to be first element");
     return top;
 }
 
-export class CompileError extends Error {
-    $loc : HDLSourceLocation;
-    constructor(msg: string, loc: HDLSourceLocation) {
-        super(msg);
-        Object.setPrototypeOf(this, CompileError.prototype);
-        this.$loc = loc;
-    }
-}
-
 export class VerilogXMLParser implements HDLUnit {
 
     files: { [id: string]: HDLFile } = {};
@@ -131,12 +132,13 @@ export class VerilogXMLParser implements HDLUnit {
     }
 
     name2js(s: string) {
+        if (s == null) throw new CompileError(null, `no name`);
         return s.replace(/[^a-z0-9_]/gi, '$');
     }
 
     findChildren(node: XMLNode, type: string, required: boolean) : XMLNode[] {
         var arr = node.children.filter((n) => n.type == type);
-        if (arr.length == 0 && required) throw Error(`no child of type ${type}`);
+        if (arr.length == 0 && required) throw new CompileError(node, `no child of type ${type}`);
         return arr;
     }
 
@@ -165,7 +167,7 @@ export class VerilogXMLParser implements HDLUnit {
             instances: [],
             vardefs: {},
         }
-        if (this.cur_module) throw new Error(`nested modules not supported`);
+        if (this.cur_module) throw new CompileError(node, `nested modules not supported`);
         this.cur_module = module;
         return module;
     }
@@ -176,8 +178,7 @@ export class VerilogXMLParser implements HDLUnit {
             this.defer(() => {
                 def.dtype = this.dtypes[dtype_id];
                 if (!def.dtype) {
-                    console.log(node);
-                    throw Error(`Unknown data type ${dtype_id} for ${node.type}`);
+                    throw new CompileError(node, `Unknown data type ${dtype_id} for ${node.type}`);
                 }
             })
         }
@@ -193,19 +194,19 @@ export class VerilogXMLParser implements HDLUnit {
             else
                 return BigInt('0x' + numstr);
         } else {
-            throw Error(`could not parse constant "${s}"`);
+            throw new CompileError(null, `could not parse constant "${s}"`);
         }
     }
     
     resolveVar(s: string, mod: HDLModuleDef) : HDLVariableDef {
         var def = mod.vardefs[s];
-        if (def == null) throw Error(`could not resolve variable "${s}"`);
+        if (def == null) throw new CompileError(null, `could not resolve variable "${s}"`);
         return def;
     }
 
     resolveModule(s: string) : HDLModuleDef {
         var mod = this.modules[s];
-        if (mod == null) throw Error(`could not resolve module "${s}"`);
+        if (mod == null) throw new CompileError(null, `could not resolve module "${s}"`);
         return mod;
     }
 
@@ -325,7 +326,7 @@ export class VerilogXMLParser implements HDLUnit {
     }
 
     visit_inititem(node: XMLNode) : HDLArrayItem {
-        if (node.children.length != 1) throw Error('expected 1 children');
+        this.expectChildren(node, 1, 1);
         return {
             index: parseInt(node.attrs['index']),
             expr: node.children[0].obj
@@ -334,7 +335,7 @@ export class VerilogXMLParser implements HDLUnit {
 
     visit_cfunc(node: XMLNode) : HDLBlock {
         if (this.cur_module == null) { // TODO?
-            console.log('no module open, skipping', node);
+            //console.log('no module open, skipping', node);
             return;
         }
         var block = this.visit_begin(node);
@@ -363,7 +364,7 @@ export class VerilogXMLParser implements HDLUnit {
     }
 
     visit_port(node: XMLNode) : HDLPort {
-        if (node.children.length != 1) throw Error('expected 1 children');
+        this.expectChildren(node, 1, 1);
         var varref: HDLPort = {
             $loc: this.parseSourceLocation(node),
             name: node.attrs['name'],
@@ -379,7 +380,12 @@ export class VerilogXMLParser implements HDLUnit {
     }
 
     visit_module_files(node: XMLNode) {
-        node.children.forEach((n) => this.files[(n.obj as HDLFile).id].isModule = true);
+        node.children.forEach((n) => {
+            if (n.obj) {
+                var file = this.files[(n.obj as HDLFile).id];
+                if (file) file.isModule = true;
+            }
+        });
     }
 
     visit_file(node: XMLNode) {
@@ -404,9 +410,12 @@ export class VerilogXMLParser implements HDLUnit {
     }
 
     visit_cells(node: XMLNode) {
+        this.expectChildren(node, 1, 9999);
         var hier = node.children[0].obj as HDLHierarchyDef;
-        var hiername = hier.name;
-        this.hierarchies[hiername] = hier;
+        if (hier != null) {
+            var hiername = hier.name;
+            this.hierarchies[hiername] = hier;
+        }
     }
 
     visit_cell(node: XMLNode) : HDLHierarchyDef {
@@ -449,8 +458,7 @@ export class VerilogXMLParser implements HDLUnit {
             default:
                 dtype = this.dtypes[dtypename];
                 if (dtype == null) {
-                    console.log(node);
-                    throw Error(`unknown data type ${dtypename}`);
+                    throw new CompileError(node, `unknown data type ${dtypename}`);
                 }
         }
         this.dtypes[id] = dtype;
@@ -471,18 +479,18 @@ export class VerilogXMLParser implements HDLUnit {
             this.dtypes[id] = dtype;
             this.defer(() => {
                 dtype.subtype = this.dtypes[sub_dtype_id];
-                if (!dtype.subtype) throw Error(`Unknown data type ${sub_dtype_id} for array`);
+                if (!dtype.subtype) throw new CompileError(node, `Unknown data type ${sub_dtype_id} for array`);
             })
             return dtype;
         } else {
-            throw Error(`could not parse constant exprs in array`)
+            throw new CompileError(node, `could not parse constant exprs in array`)
         }
     }
 
     visit_senitem(node: XMLNode) : HDLSensItem {
         var edgeType = node.attrs['edgeType'];
         if (edgeType != "POS" && edgeType != "NEG")
-            throw Error("POS/NEG required")
+            throw new CompileError(node, "POS/NEG required")
         return {
             $loc: this.parseSourceLocation(node),
             edgeType: edgeType,
@@ -505,8 +513,13 @@ export class VerilogXMLParser implements HDLUnit {
     visit_constpool(node: XMLNode) {
     }
 
+    expectChildren(node: XMLNode, low: number, high: number) {
+        if (node.children.length < low || node.children.length > high)
+            throw new CompileError(node, `expected between ${low} and ${high} children`);
+    }
+
     __visit_unop(node: XMLNode) : HDLUnop {
-        if (node.children.length != 1) throw Error('expected 1 children');
+        this.expectChildren(node, 1, 1);
         var expr: HDLUnop = {
             $loc: this.parseSourceLocation(node),
             op: node.type,
@@ -521,12 +534,12 @@ export class VerilogXMLParser implements HDLUnit {
         var unop = this.__visit_unop(node) as HDLExtendop;
         unop.width = parseInt(node.attrs['width']);
         unop.widthminv = parseInt(node.attrs['widthminv']);
-        if (unop.width != 32) throw Error(`extends width ${unop.width} != 32`)
+        if (unop.width != 32) throw new CompileError(node, `extends width ${unop.width} != 32`)
         return unop;
     }
 
     __visit_binop(node: XMLNode) : HDLBinop {
-        if (node.children.length != 2) throw Error('expected 2 children');
+        this.expectChildren(node, 2, 2);
         var expr: HDLBinop = {
             $loc: this.parseSourceLocation(node),
             op: node.type,
@@ -539,7 +552,7 @@ export class VerilogXMLParser implements HDLUnit {
     }
 
     visit_if(node: XMLNode) : HDLTriop {
-        if (node.children.length < 2 || node.children.length > 3) throw Error('expected 2 or 3 children');
+        this.expectChildren(node, 2, 3);
         var expr: HDLTriop = {
             $loc: this.parseSourceLocation(node),
             op: 'if',
@@ -553,7 +566,7 @@ export class VerilogXMLParser implements HDLUnit {
 
     // while and for loops
     visit_while(node: XMLNode) : HDLWhileOp {
-        if (node.children.length < 2 || node.children.length > 4) throw Error('expected 2-4 children');
+        this.expectChildren(node, 2, 4);
         var expr: HDLWhileOp = {
             $loc: this.parseSourceLocation(node),
             op: 'while',
@@ -567,7 +580,7 @@ export class VerilogXMLParser implements HDLUnit {
     }
 
     __visit_triop(node: XMLNode) : HDLBinop {
-        if (node.children.length != 3) throw Error('expected 2 children');
+        this.expectChildren(node, 3, 3);
         var expr: HDLTriop = {
             $loc: this.parseSourceLocation(node),
             op: node.type,
@@ -677,8 +690,7 @@ export class VerilogXMLParser implements HDLUnit {
         if (method) {
             return method.bind(this)(node);
         } else {
-            console.log(node);
-            throw Error(`no visitor for ${node.type}`)
+            throw new CompileError(node, `no visitor for ${node.type}`)
         }
     }
 
diff --git a/src/common/hdl/vxmltest.ts b/src/common/hdl/vxmltest.ts
index 62fb60ad..3f75ef43 100644
--- a/src/common/hdl/vxmltest.ts
+++ b/src/common/hdl/vxmltest.ts
@@ -107,6 +107,6 @@ async function testJSvsWASM() {
     }
 }
 
-testJSvsWASM();
-//testWASM().then(testJS);
+//testJSvsWASM();
+testWASM().then(testJS).then(testJSvsWASM);